Nature Energy

In wind farms, turbines are operated to maximize only their own power production. Individual operation results in wake losses that reduce farm energy. Here we operate a wind turbine array collectively to maximize array production through wake steering. We develop a physics-based, data-assisted flow control model to predict the power-maximizing control strategy. We first validate the model with a multi-month field experiment at a utility-scale wind farm. The model is able to predict the yaw-misalignment angles which maximize array power production within ± 5° for most wind directions (5–32% gains). Using the validated model, we design a control protocol which increases the energy production of the farm in a second multi-month experiment by 3.0% ± 0.7% and 1.2% ± 0.4% for wind speeds between 6 m s−1 and 8 m s−1  and all wind speeds, respectively. The predictive model can enable a wider adoption of collective wind farm operation. Individual operation of turbines in wind farms results in energy losses from wake interactions. Here Howland et al. report on an experimentally validated model to implement collective operation of turbines, which increases the farm’s energy production.

Water electrolysis is a key technology to establish CO 2 -neutral hydrogen production. Nonetheless, the near-surface structure of electrocatalysts during the anodic oxygen evolution reaction (OER) is still largely unknown, which hampers knowledge-driven optimization. Here using operando X-ray absorption spectroscopy and density functional theory calculations, we provide quantitative near-surface structural insights into oxygen-evolving CoO x (OH) y nanoparticles by tracking their size-dependent catalytic activity down to 1 nm and their structural adaptation to OER conditions. We uncover a superior intrinsic OER activity of sub-5 nm nanoparticles and a size-dependent oxidation leading to a near-surface Co–O bond contraction during OER. We find that accumulation of oxidative charge within the surface Co ³⁺ O 6 units triggers an electron redistribution and an oxyl radical as predominant surface-terminating motif. This contrasts the long-standing view of high-valent metal ions driving the OER, and thus, our advanced operando spectroscopy study provides much needed fundamental understanding of the oxygen-evolving near-surface chemistry.

Understanding what drives household-level decisions to keep cooking with polluting cookstoves and fuels must be grounded in theory for sustained change to occur. New research examines the literature through a behavioural model and finds that affordability, technical aspects, and fuel supply are the main drivers of fuel stacking.

In recent years, the investment community has become increasingly aware of the investment risks from both the physical effects of climate change and the regulatory responses to facilitate the transition to a net-zero economy. The potential impact of climate transition risks is especially large for fossil energy companies, given their central role in producing carbon emissions. Here we discuss how concerns about climate risks influence the way investors allocate their capital and exercise their oversight of firms, and how this investor response affects companies in the energy sector. We then explore how different energy firms have responded to climate-related pressures from their investors and other stakeholders. We conclude by highlighting promising areas of research for understanding how climate risks affect the interaction between financial markets and the energy sector. Managing climate risk exposures of assets and loan portfolios is increasingly important for actors within financial markets. This Review examines how such risks affect investor behaviour and hence the wider energy sector, and highlights areas for future research into the interactions between them.

Hard to decarbonize homes represent a complex problem that has historically been neglected in favour of the lower hanging fruit of easier to treat properties. To enable an equitable net zero transition, we must understand these homes in a holistic manner take into account the impacts of different routes to decarbonization on occupants.

Globally, 2.8 billion people cook with biomass fuels, resulting in devastating health and environmental consequences. Efforts to transition households to cooking with clean fuels are hampered by ‘fuel stacking’, the reliance on multiple fuels and stoves. Consequently, there have been few interventions that have realized the full potential of clean cooking. Here we conduct a structured literature review (N = 100) to identify drivers of fuel stacking and specify them according to a psychological model of behaviour, the Capability–Opportunity–Motivation (COM-B) model. We create a taxonomy of stacking and find that the Physical Opportunity domain accounted for 82% of drivers. Our results have important implications for intervention design as they suggest improving opportunity is the most effective pathway to adoption of cleaner fuels. The findings are used to derive recommendations about how policymakers and practitioners can proactively address drivers of stacking to foster adoption of clean cooking stoves and fuels. Realizing the full potential of clean cooking transitions requires an understanding of fuel stacking in which multiple fuels and stoves are used. Towards this end, Perros et al. analyse the literature on clean cooking interventions through a behavioural model and identify underlying drivers of stacking.

The broad bandgap tunability of organic–inorganic metal halide perovskites enables the fabrication of multi-junction all-perovskite tandem solar cells with ultra-high power conversion efficiencies (PCEs). Controllable crystallization plays a crucial role in the formation of high-quality perovskites. Here we report a universal close-space annealing strategy that increases grain size, enhances crystallinity and prolongs carrier lifetimes in low-bandgap (low-Eg) and wide-bandgap (wide-Eg) perovskite films. By placing the intermediate-phase perovskite films with their faces towards solvent-permeable covers during the annealing process, high-quality perovskite absorber layers are obtained with a slowed solvent releasing process, enabling fabrication of efficient single-junction perovskite solar cells (PVSCs) and all-perovskite tandem solar cells. As a result, the best PCEs of 21.51% and 18.58% for single-junction low-Eg and wide-Eg PVSCs are achieved and thus ensure the fabrication of 25.15% efficiency 4-terminal and 25.05% efficiency 2-terminal all-perovskite tandem solar cells.

Understanding carrier loss mechanisms at microscopic regions is imperative for the development of high-performance polycrystalline inorganic thin-film solar cells. Despite the progress achieved for kesterite, a promising environmentally benign and earth-abundant thin-film photovoltaic material, the microscopic carrier loss mechanisms and their impact on device performance remain largely unknown. Herein, we unveil these mechanisms in state-of-the-art Cu2ZnSnSe4 (CZTSe) solar cells using a framework that integrates multiple microscopic and macroscopic characterizations with three-dimensional device simulations. The results indicate the CZTSe films have a relatively long intragrain electron lifetime of 10–30 ns and small recombination losses through bandgap and/or electrostatic potential fluctuations. We identify that the effective minority carrier lifetime of CZTSe is dominated by a large grain boundary recombination velocity (~10⁴ cm s⁻¹), which is the major limiting factor of present device performance. These findings and the framework can greatly advance the research of kesterite and other emerging photovoltaic materials.

As climate change accelerates, governments will be forced to adapt to its impacts. The public could respond by increasing mitigation behaviours and support for decarbonization, creating a virtuous cycle between adaptation and mitigation. Alternatively, adaptation could generate backlash, undermining mitigation behaviours. Here we examine the relationship between adaptation and mitigation in the power sector, using the case of California’s public safety power shut-offs in 2019. We use a geographically targeted survey to compare residents living within power outage zones to matched residents in similar neighbourhoods who retained their electricity. Outage exposure increased respondent intentions to purchase fossil fuel generators while it may have reduced intentions to purchase electric vehicles. However, exposure did not change climate policy preferences, including willingness to pay for either wildfire or climate-mitigating reforms. Respondents blamed outages on their utility, not local, state or federal governments. Our findings demonstrate that energy infrastructure disruptions, even when not understood as climate adaptations, can still be consequential for decarbonization trajectories. Climate change adaptation policies could influence public decarbonization behaviours positively or negatively, impacting further mitigation and adaptation efforts. This study examines public responses to planned power outages in California and finds that the outages shaped some energy behavioural intentions but did not alter climate or energy policy preferences.

Whether additional natural gas infrastructure is needed or would be detrimental to achieving climate protection goals is currently highly controversial. Here we combine five perspectives to argue why expansion of the natural gas infrastructure hinders a renewable energy future and is no bridge technology. We highlight that natural gas is a fossil fuel with a significantly underestimated climate impact that hinders decarbonization through carbon lock-in and stranded assets. We propose five ways to avoid common shortcomings for countries that are developing strategies for greenhouse gas reduction: manage methane emissions of the entire natural gas value chain, revise assumptions of scenario analyses with new research insights on greenhouse gas emissions related to natural gas, replace the ‘bridge’ narrative with unambiguous decarbonization criteria, avoid additional natural gas lock-ins and methane leakage, and take climate-related risks in energy infrastructure planning seriously.

Flexible all-perovskite tandem photovoltaics open up new opportunities for application compared to rigid devices, yet their performance lags behind. Now, researchers show that molecule-bridged interfaces mitigate charge recombination and crack formation, improving the efficiency and mechanical reliability of flexible devices.

In the intensive search for novel battery architectures, the spotlight is firmly on solid-state lithium batteries. Now, a strategy based on solid-state sodium–sulfur batteries emerges, making it potentially possible to eliminate scarce materials such as lithium and transition metals.

One of the key targets for further development of sodium-ion batteries is to improve their cycle life. Now, an electrolyte formulation is proposed to tackle the dissolution of both the solid-electrolyte interphases and the transition metals in cathodes, leading to enhanced cyclability.

International maritime shipping—powered by heavy fuel oil—is a major contributor to global CO2, SO2, and NOx emissions. The direct electrification of maritime vessels has been underexplored as a low-emission option despite its considerable efficiency advantage over electrofuels. Past studies on ship electrification have relied on outdated assumptions on battery cost, energy density values and available on-board space. We show that at battery prices of US$100 kWh−1 the electrification of intraregional trade routes of less than 1,500 km is economical, with minimal impact to ship carrying capacity. Including the environmental costs increases the economical range to 5,000 km. If batteries achieve a US$50 kWh−1 price point, the economical range nearly doubles. We describe a pathway for the battery electrification of containerships within this decade that electrifies over 40% of global containership traffic, reduces CO2 emissions by 14% for US-based vessels, and mitigates the health impacts of air pollution on coastal communities. The maritime shipping industry is heavily energy-consuming and highly polluting, and, as such, is urgently seeking low-emission options. Here the authors examine the feasibility of battery-electric ships and show that the battery price declines could facilitate the electrification of short to medium-range shipping.

Critics have opposed clean energy public investment by claiming that governments must not pick winners, green subsidies enable rent-seeking behaviour, and failed companies means failed policy. These arguments are problematic and should not determine the direction of energy investment policies.

Electrification models used to plan future energy systems have become increasingly sophisticated, but typically oversimplify the financial landscape. New research shows that more accurate accounting of the costs of capital significantly changes the least-cost pathway to providing electrification across sub-Saharan Africa.

The UN Sustainable Development Goal 7 (SDG 7) on energy access and Goal 5 (SDG 5) on gender equality are inextricably linked. A new study utilizing field-based data from India unpacks how levels of women’s empowerment in households influences their awareness, usage, satisfaction, and preference for energy services.

Metal halide perovskite solar cells have shown promising performance, but mainly on small-area devices and under laboratory conditions. Now, researchers have demonstrated the fabrication of large-area devices assembled and packaged into modules and reported on their operation outdoors.

Nitrogen-coordinated iron catalysts are exciting potential replacements for platinum at the cathode of proton-exchange membrane fuel cells, but still tend to have poor long-term durability. Now, a thin and porous nitrogen-doped carbon film deposited at the surface of a highly active but unstable Fe–N–C catalyst is shown to drastically improve its stability.

Nitrogen-coordinated single atom iron sites (FeN4) embedded in carbon (Fe–N–C) are the most active platinum group metal-free oxygen reduction catalysts for proton-exchange membrane fuel cells. However, current Fe–N–C catalysts lack sufficient long-term durability and are not yet viable for practical applications. Here we report a highly durable and active Fe–N–C catalyst synthesized using heat treatment with ammonia chloride followed by high-temperature deposition of a thin layer of nitrogen-doped carbon on the catalyst surface. We propose that catalyst stability is improved by converting defect-rich pyrrolic N-coordinated FeN4 sites into highly stable pyridinic N-coordinated FeN4 sites. The stability enhancement is demonstrated in membrane electrode assemblies using accelerated stress testing and a long-term steady-state test (>300 h at 0.67 V), approaching a typical Pt/C cathode (0.1 mgPt cm−2). The encouraging stability improvement represents a critical step in developing viable Fe–N–C catalysts to overcome the cost barriers of hydrogen fuel cells for numerous applications. Fe–N–C materials are promising oxygen reduction catalysts for proton-exchange membrane fuel cells but still lack sufficient long-term durability for practical applications. Here the authors fabricate an Fe–N–C material with a thin N–C layer on the surface, leading to a highly durable and active catalyst.

Monolithic all-perovskite tandem photovoltaics promise to combine low-cost and high-efficiency solar energy harvesting with the advantages of all-thin-film technologies. To date, laboratory-scale all-perovskite tandem solar cells have only been fabricated using non-scalable fabrication techniques. In response, this work reports on laser-scribed all-perovskite tandem modules processed exclusively with scalable fabrication methods (blade coating and vacuum deposition), demonstrating power conversion efficiencies up to 19.1% (aperture area, 12.25 cm2; geometric fill factor, 94.7%) and stable power output. Compared to the performance of our spin-coated reference tandem solar cells (efficiency, 23.5%; area, 0.1 cm2), our prototypes demonstrate substantial advances in the technological readiness of all-perovskite tandem photovoltaics. By means of electroluminescence imaging and laser-beam-induced current mapping, we demonstrate the homogeneous current collection in both subcells over the entire module area, which explains low losses (<5%rel) in open-circuit voltage and fill factor for our scalable modules. All-perovskite tandem photovoltaics hold technological potential yet their upscaling is not trivial. Here Nejand et al. fabricate mini-modules using scalable methods and laser-scribed interconnections, achieving a 19.1% efficiency over an aperture area of 12.25 cm2.

Legal mandates are critical to supporting action on sustainable development goals and climate change targets. Yet, new research highlights the importance of initial endowments for energy transitions, and how they can lead to disparate outcomes across regions.

The capacity factor (cf) is a critical variable for quantifying wind turbine efficiency. Climate change-induced wind resource variations and technical wind turbine fleet development will alter future cfs. Here we define 12 techno-climatic change scenarios to assess regional and global onshore cfs in 2021–2060. Despite a decreasing global wind resource, we find an increase in future global cf caused by fleet development. The increase is significant under all evaluated techno-climatic scenarios. Under the likely emissions scenario Shared Socioeconomic Pathway 2–4.5, global cf increases from 0.251 in 2021 up to 0.310 in 2035 under ambitious fleet development. This cf enhancement is equivalent to a 361 TWh yield improvement under the globally installed capacity of 2020 (698 GW). To increase the contribution of the future wind turbine fleet to the Intergovernmental Panel on Climate Change climate protection goals, we recommend a rapid wind turbine fleet conversion.

As a vital step towards the industrialization of perovskite solar cells, outdoor field tests of large-scale perovskite modules and panels represent a mandatory step to be accomplished. Here we demonstrate the manufacturing of large-area (0.5 m²) perovskite solar panels, each containing 40 modules whose interfaces are engineered with two-dimensional materials (GRAphene-PErovskite (GRAPE) panels). We further integrate nine GRAPE panels for a total panel area of 4.5 m² in a stand-alone solar farm infrastructure with peak power exceeding 250 W, proving the scalability of this technology. We provide insights on the system operation by analysing the panel characteristics as a function of temperature and light intensity. The analysis, carried out over a months-long timescale, highlights the key role of the lamination process of the panels on the entire system degradation. A life-cycle assessment based on primary data indicates the high commercial potential of the GRAPE panel technology in terms of energy and environmental performances.

All-perovskite tandem solar cells are promising for achieving photovoltaics with power conversion efficiencies above the detailed balance limit of single-junction cells, while retaining the low cost, light weight and other advantages associated with metal halide perovskite photovoltaics. However, the efficiency and stability of all-perovskite tandem cells are limited by the Sn–Pb-based narrow-bandgap perovskite cells. Here we show that the formation of quasi-two-dimensional (quasi-2D) structure (PEA)2GAPb2I7 from additives based on mixed bulky organic cations phenethylammonium (PEA+) and guanidinium (GA+) provides critical defect control to substantially improve the structural and optoelectronic properties of the narrow-bandgap (1.25 eV) Sn–Pb perovskite thin films. This 2D additive engineering results in Sn–Pb-based absorbers with low dark carrier density (~1.3 × 1014 cm−3), long bulk carrier lifetime (~9.2 μs) and low surface recombination velocity (~1.4 cm s−1), leading to 22.1%-efficient single-junction Sn–Pb perovskite cells and 25.5%-efficient all-perovskite two-terminal tandems with high photovoltage and long operational stability. Tong et al. form a 2D perovskite layer with two large organic cations to improve the structural and optoelectronic properties of Sn–Pb perovskites, and eventually the performance of single-junction and tandem solar cells.

Electrifying 600 million people in sub-Saharan Africa will require substantial investments. Integrated electrification models inform key policy decisions and electricity access investments in many countries. While current electrification models apply sophisticated geospatial methods, they often make simplistic assumptions about financing conditions. Here we establish cost of capital values, reflecting country and electrification mode (that is, grid extension, minigrids and stand-alone systems), and specific risks faced by investors and integrate them into an open source electrification model. We find that the cost of capital for off-grid electrification is much higher than currently assumed, up to 32.2%. Accounting for finance shifts approximately 240 million people from minigrids to stand-alone systems in our main scenario, suggesting a more cost-effective electrification mode mix than previously suggested. In turn, electrification models based on uniform cost of capital assumptions increase the per kWh cost of electricity by 20%, on average. Upscaling and mainstreaming off-grid finance can lower electrification cost substantially.

The achievement of sustainable energy systems requires well-designed energy policies, particularly targeted strategies to plan the direction of energy development, regulations monitored and executed through credible authorities and laws enforced by the judicial system for the enhancement of actions and national targets. The Asia–Pacific region (APAC), responsible for more than half of global energy consumption, has enacted a large number of energy policies over the past two decades, but progress on the energy transition remains slow. This study focuses on the aggregate effect of energy policies on the progress towards sustainable targets in 42 emerging economies from 2000 to 2017. We find that energy policies have contributed to improving access to electricity (3.0%), access to clean cooking (3.8%), energy efficiency (1.4%) and renewable electricity capacity (6.9%), respectively. Among different types of energy policy (strategies, laws and regulations), strategies have greater impacts on advancing electrification, clean cooking and renewable electricity capacity than laws and regulations, whereas the laws are more effective for achieving energy efficiency.

In recent years, global studies have attempted to understand the contribution that energy demand reduction could make to climate mitigation efforts. Here we develop a bottom-up, whole-system framework that comprehensively estimates the potential for energy demand reduction at a country level. Replicable for other countries, our framework is applied to the case of the United Kingdom where we find that reductions in energy demand of 52% by 2050 compared with 2020 levels are possible without compromising on citizens’ quality of life. This translates to annual energy demands of 40 GJ per person, compared with the current Organisation for Economic Co-operation and Development average of 116 GJ and the global average of 55 GJ. Our findings show that energy demand reduction can reduce reliance on high-risk carbon dioxide removal technologies, has moderate investment requirements and allows space for ratcheting up climate ambition. We conclude that national climate policy should increasingly develop and integrate energy demand reduction measures.

Sodium-ion batteries (NIBs) have attracted worldwide attention for next-generation energy storage systems. However, the severe instability of the solid–electrolyte interphase (SEI) formed during repeated cycling hinders the development of NIBs. In particular, the SEI dissolution in NIBs with a high-voltage cathode is more severe than in the case of Li-ion batteries (LIBs) and leads to continuous side reactions, electrolyte depletion and irreversible capacity loss, making NIBs less stable than LIBs. Here we report a rational electrolyte design to suppress the SEI dissolution and enhance NIB performance. Our electrolyte lowers the solvation ability for SEI components and facilitates the formation of insoluble SEI components, which minimizes the SEI dissolution. In addition to the stable SEI on a hard carbon (HC) anode, we also show a stable interphase formation on a NaNi0.68Mn0.22Co0.1O2 (NaNMC) cathode. Our HC||NaNMC full cell with this electrolyte demonstrates >90% capacity retention after 300 cycles when charged to 4.2 V. This study enables high-voltage NIBs with long cycling performance and provides a guiding principle in electrolyte design for sodium-ion batteries.

Energy access delivers broad socio-economic benefits, but few studies have examined how benefits are allocated within the household. Here we conduct a large-scale survey with 4,624 respondents across six Indian states to provide results on intra-household differences across multiple outcome dimensions of energy service, including knowledge, satisfaction, utilization and opinion. Using a Women’s Empowerment Index (WEI) to measure household-level gender equality, we find that women in low-WEI households are less aware of energy services and use less electricity than their spouses. This awareness gap manifests in differences in satisfaction, as women in higher-WEI households show more concern with energy services and fuel sources. Overall, these results signify that the ‘one-size-fits-all’ approach of providing energy access may not effectively meet the goal of sustainable energy for all. Bridging the gender gap through targeted information and learning campaigns that empower and educate women could unlock additional support for sustainable energy policies. Improved energy access can bring socio-economic benefits, yet these may not be evenly distributed within the household. Zhang et al. conduct a large-scale survey in India and find gender-based disparities in energy services within households.

Lightweight flexible perovskite solar cells are promising for building integrated photovoltaics, wearable electronics, portable energy systems and aerospace applications. However, their highest certified efficiency of 19.9% lags behind their rigid counterparts (highest 25.7%), mainly due to defective interfaces at charge-selective contacts with perovskites on top. Here we use a mixture of two hole-selective molecules based on carbazole cores and phosphonic acid anchoring groups to form a self-assembled monolayer and bridge perovskite with a low temperature-processed NiO nanocrystal film. The hole-selective contact mitigates interfacial recombination and facilitates hole extraction. We show flexible all-perovskite tandem solar cells with an efficiency of 24.7% (certified 24.4%), outperforming all types of flexible thin-film solar cell. We also report 23.5% efficiency for larger device areas of 1.05 cm². The molecule-bridged interfaces enable significant bending durability of flexible all-perovskite tandem solar cells that retain their initial performance after 10,000 cycles of bending at a radius of 15 mm.

Oxygen redox at high voltage has emerged as a transformative paradigm for high-energy battery cathodes such as layered transition-metal oxides by offering extra capacity beyond conventional transition-metal redox. However, these cathodes suffer from voltage hysteresis, voltage fade and capacity drop upon cycling. Single-crystalline cathodes have recently shown some improvements, but these challenges remain. Here we reveal the fundamental origin of oxygen redox instability to be from the domain boundaries that are present in single-crystalline cathode particles. By investigating single-crystalline cathodes with different domain boundaries structures, we show that the elimination of domain boundaries enhances the reversible lattice oxygen redox while inhibiting the irreversible oxygen release. This leads to significantly suppressed structural degradation and improved mechanical integrity during battery cycling and abuse heating. The robust oxygen redox enabled through domain boundary control provides practical opportunities towards high-energy, long-cycling, safe batteries. Oxygen redox instability at high voltages hinders the application of high-energy battery cathodes. Here the authors report that elimination of domain boundaries in single-crystal cathodes improves the redox stability and consequently the electrochemical performance in extended high-voltage cycling.

All-perovskite tandem devices are promising due to their high efficiency and low cost but their development is hindered by narrow-bandgap absorbers. Now, researchers combine two large organic cations to improve the optoelectronic quality of narrow-bandgap tin–lead perovskites, enabling single-junction and tandem cells with enhanced efficiency and stability.

High-performance electrolytes are urgently required in the development of reversible lithium-metal batteries that offer high energy densities. Now, a versatile liquefied gaseous electrolyte is demonstrated with inherent safety, temperature resilience, high recyclability, and promising electrochemical properties.

Controlling the crystallization of perovskite films over large areas is key to the manufacturing of solar cells, but is difficult with existing fabrication methods. Now, researchers tailor the composition of the precursor ink to fabricate uniform and phase-pure perovskite layers, enabling a 15.3%-efficient photovoltaic module with an area of 205 cm2.

High-energy density, improved safety, temperature resilience and sustainability are desirable properties for lithium-battery electrolytes, yet these metrics are rarely achieved simultaneously. Inspired by the compositions of clean fire-extinguishing agents, we demonstrate inherently safe liquefied gas electrolytes based on 1,1,1,2-tetrafluoroethane and pentafluoroethane that maintain >3 mS cm⁻¹ ionic conductivity from −78 to +80 °C. As a result of beneficial solvation chemistry and a fluorine-rich environment, lithium cycling at >99% Coulombic efficiency for over 200 cycles at 3 mA cm⁻² and 3 mAh cm⁻² was demonstrated in addition to stable cycling of Li/NMC622 full batteries from −60 to +55 °C. In addition, we demonstrate a one-step solvent-recycling process based on the vapour pressure difference at different temperatures of the liquefied gas electrolytes, which promises sustainable operation at scale. This work provides a route to sustainable, temperature-resilient lithium-metal batteries with fire-extinguishing properties that maintain state-of-the-art electrochemical performance.

Photoelectrochemical water splitting is an attractive solar-to-hydrogen pathway. However, the lifetime of photoelectrochemical devices is hampered by severe photocorrosion of semiconductors and instability of co-catalysts. Here we report a strategy for stabilizing photoelectrochemical devices that use a polyacrylamide hydrogel as a highly permeable and transparent device-on-top protector. A hydrogel-protected Sb2Se3 photocathode exhibits stability over 100 h, maintaining ~70% of the initial photocurrent, and the degradation rate gradually decreases to the saturation level. The structural stability of a Pt/TiO2/Sb2Se3 photocathode remains unchanged beyond this duration, and effective bubble escape is ensured through the micro gas tunnel formed in the hydrogel to achieve a mechanically stable protector. We demonstrate the versatility of the device-on-top hydrogel protector under a wide electrolyte pH range and by using a SnS photocathode and a BiVO4 photoanode with ~500 h of lifetime.

Traditional centralized optimization and management schemes may be incompatible with a changing energy system whose structure is becoming increasingly distributed. This challenge can hopefully be addressed by blockchain. However, existing blockchains have not been well prepared to integrate mathematical optimization, which plays a key role in many energy system applications. Here we propose a blockchain consensus mechanism tailored to support mathematical optimization problems, called Proof of Solution (PoSo). PoSo mimics Proof of Work (PoW) by replacing the meaningless mathematical puzzle in PoW with a meaningful optimization problem. This is inspired by the fact that both the solutions to the puzzle and to an optimization problem are hard to find but easy to verify. We show the security and necessity of PoSo by using PoSo to enable energy dispatch and trading for two integrated energy systems. The results show that compared with existing optimization schemes, PoSo ensures that only the optimal solution is accepted and executed by participants. Further, compared with existing blockchains, PoSo can seamlessly incorporate mathematical optimization and minimize the workload associated with searching and verifying the optimum.

Sodium-based batteries have attracted wide interests in the academic and industrial fields. However, their energy density is still lower than that of Li-based batteries. Here we report an initial anode-free Na battery with an energy density of over 200 Wh kg−1, which is even higher than that of the commercial LiFePO4||graphite battery. Through introducing graphitic carbon coating on the Al current collector and boron-containing electrolytes in the battery, we show that uniform nucleation and robust interphases enable reversible and crack-free Na deposition. Benefitting from the synergetic effects derived from the built cooperative interfaces, the cycling lifetime of the Na battery without applying additional pressure reaches 260 cycles, which is the longest life for large-size cells with zero excess Na. The insights gained from the Na plating/stripping behaviour and interfacial chemistry in this work pave the way for further development of Na batteries with even higher performance. Sodium-ion batteries have long been tipped as a promising post-Li-ion storage technology but their performance is still inferior to Li-ion batteries. Here the authors design an ampere-hour-scale battery with an initial Na-free anode configuration to achieve an energy density that rivals Li-ion batteries.

Blockchains offer a lot of opportunities for efficiency and decentralized management in energy systems. Researchers now show the electricity dispatch is a useful problem uniquely suited to serve as proof of work in a new consensus mechanism for decentralized grid management.