Huan Huang’s research while affiliated with Institute of High Energy Physics, Chinese Academy of Sciences and other places

In order to expand the range of synchrotron radiation structural characterization modes, an automated in-situ X-ray absorption fine structure (XAFS) spectroscopy characterization for electrochemical research has been established. An in-situ control system equipped with an automatic trigger capability facilitates automated acquisition of XAFS and electrochemical data. Furthermore, the quick scanning XAFS (QXAFS) terminal, in-situ server and data storage were all controlled by remote users, enabling remote measurement to be achieved. Using this system, the evolution of the local structure near Fe atoms during the charging and discharging of lithium-sulfur battery (LSB) cathode materials was observed, which provides deep insights into the sulfur reaction pathway in LSBs by leveraging structural information. The system established here paves the way for fully automated and intelligent in-situ XAFS experiments.

Learning from nature has garnered significant attention in the scientific community for its potential to inspire creative solutions in material or catalyst design. The study highlights the design of a biomimetic single selenium (Se) site‐modified carbon (C) moiety that retains the unique reactivity of selenoenzyme with peroxides, which plays crucial roles in selectively catalyzing the oxygen reduction reaction (ORR). The as‐designed Se−C demonstrates nearly 100 % 4‐electron selectivity, evidenced by 0.039 % of H2O2 yield at 0.5 V versus reversible hydrogen electrode, outperforming commercial platinum (Pt) by 65 times. In situ X‐ray absorption spectroscopy and theoretical calculations attribute this exceptional selectivity to the enzyme‐like behaviors of the Se site to steal an O atom from peroxide intermediates. The second achievement is the significantly increased consecutive 2+2 electron selectivity. Benefiting from the enzyme‐like H2O2 reduction activity with a higher onset potential of 0.915 V compared to Pt at 0.875 V, the Se−C as a secondary catalytic site reduced the H2O2 yields of the Co−N−C, Fe−N−C, and N−C catalysts by 96 %, 67 %, and 98 %, respectively, via a consecutive 2+2 electron pathway. This also leads to more stable catalysts via protecting the active sites from oxidative attacks. This work establishes new pathways for precise tuning of reaction selectivity in ORR and beyond.

Learning from nature has garnered significant attention in the scientific community for its potential to inspire creative solutions in material or catalyst design. The study reports a biomimetic single selenium (Se) site‐modified carbon (C) moiety that retains the unique reactivity of selenoenzyme with peroxides, aiming to selectively catalyze the oxygen reduction reaction (ORR). The as‐designed Se‐C demonstrates nearly 100% 4‐electron selectivity, evidenced by 0.039% of H2O2 yield at 0.5 V versus reversible hydrogen electrode, outperforming commercial platinum (Pt) by 65 times. In‐situ X‐ray absorption spectroscopy and theoretical calculations attribute this exceptional selectivity to the enzyme‐like behaviors of the Se site to steal an O atom from peroxide intermediates. The second achievement is the significantly increased consecutive 2+2 electron selectivity. Benefiting from the enzyme‐like H2O2 reduction activity with a higher onset potential of 0.915 V compared to Pt at 0.875 V, the Se‐C as a secondary catalytic site reduced the H2O2 yields of the Co‐N‐C, Fe‐N‐C, and N‐C catalysts by 96%, 67%, and 98%, respectively, via a consecutive 2+2 electron pathway. This also leads to more stable catalysts via protecting the active sites from oxidative attacks. This work establishes new pathways for precise tuning of reaction selectivity in ORR and beyond.

Efforts to improve the specific capacity and energy density of lithium nickel-cobalt-manganese oxide (NCM) cathodes focus on operating at high voltages or increasing nickel content. However, both approaches necessitate a...

More and more basic practical application scenarios have been gradually ignored/disregarded, in fundamental research on rechargeable batteries, e.g. assessing cycle life under various depths‐of‐discharge (DODs). Herein, although benefit from the additional energy density introduced by anionic redox, we critically revealed that lithium‐rich layered oxide (LRLO) cathodes present anomalously poor capacity retention at low‐DOD cycling, which is essentially different from typical layered cathodes (e.g. NCM), and pose a formidable impediment to the practical application of LRLO. We systemically demonstrated that DOD‐dependent capacity decay is induced by the anionic redox and accumulation of oxidized lattice oxygen (Oⁿ⁻). Upon low‐DOD cycling, the accumulation of Oⁿ⁻ and the persistent presence of vacancies in the transition metal (TM) layer intensified the in‐plane migration of TM, exacerbating the expansion of vacancy clusters, which further facilitated detrimental out‐of‐plane TM migration. As a result, the aggravated structural degradation of LRLO at low‐DOD impeded reversible Li⁺ intercalation, resulting in rapid capacity decay. Furthermore, prolonged accumulation of Oⁿ⁻ persistently corroded the electrode‐electrolyte interface, especially negative for pouch‐type full‐cells with the shuttle effect. Once the “double‐edged sword” effect of anionic redox being elucidated under practical condition, corresponding modification strategies/routes would become distinct for accelerating the practical application of LRLO.

More and more basic practical application scenarios have been gradually ignored/disregarded, in fundamental research on rechargeable batteries, e.g. assessing cycle life under various depths‐of‐discharge (DODs). Herein, although benefit from the additional energy density introduced by anionic redox, we critically revealed that lithium‐rich layered oxide (LRLO) cathodes present anomalously poor capacity retention at low‐DOD cycling, which is essentially different from typical layered cathodes (e.g. NCM), and pose a formidable impediment to the practical application of LRLO. We systemically demonstrated that DOD‐dependent capacity decay is induced by the anionic redox and accumulation of oxidized lattice oxygen (On‐). Upon low‐DOD cycling, the accumulation of On‐ and the persistent presence of vacancies in the transition metal (TM) layer intensified the in‐plane migration of TM, exacerbating the expansion of vacancy clusters, which further facilitated detrimental out‐of‐plane TM migration. As a result, the aggravated structural degradation of LRLO at low‐DOD impeded reversible Li+ intercalation, resulting in rapid capacity decay. Furthermore, prolonged accumulation of On‐ persistently corroded the electrode‐electrolyte interface, especially negative for pouch‐type full‐cells with the shuttle effect. Once the “double‐edged sword” effect of anionic redox being elucidated under practical condition, corresponding modification strategies/routes would become distinct for accelerating the practical application of LRLO.

Layered oxide cathodes encounter structural challenges during cycling, prompting the exploration of an ingenious heterostructure strategy, which incorporates stable components into the layered structure as strain regulators to enhance materials cycle stability. Despite considerable research efforts, identifying suitable, convenient, and cost-effective materials and methods remains elusive. Herein, focused on lithium cobalt oxide (LiCoO2), we utilized its low-temperature polymorph as a strain-retardant embedded within a cathode. Our findings reveal that the low-temperature component, exhibiting zero-strain characteristic, adopts a complex configuration with a predominant lithiated spinel structure, also featuring both cubic-layered and typical-layered configurations. But this composite cathode exhibits a sluggish lithium-ion transport rate, attributed to Co&Li dislocation at the dual structural boundaries and the formation of cobalt(iii) oxide. This investigation presents a pioneering endeavor in employing heterostructure strategies, underscoring the critical role of such strategies in component selection, which ultimately propels the advancement of layered oxide cathode candidates for Li-ion battery technology.

Replacement of expensive and rare platinum with metal–nitrogen–carbon catalysts for oxygen reduction reactions in proton exchange membrane fuel cells is hindered by their inferior activity. Herein, we report a highly active iron-nitrogen-carbon catalyst by optimizing the carbon structure and coordination environments of Fe-N4 sites. A critical high-temperature treatment with ammonium chloride and ammonium bromide not only enhances the intrinsic activity and density of Fe-N4 sites, but also introduces numerous defects, trace Br ions and creates mesopores in the carbon framework. Notably, surface Br ions significantly improve the interaction between the ionomer and catalyst particles, promoting ionomer infiltration and optimizing the O2 transport and charge transfer at triple-phase boundary. This catalyst delivers a high peak power density of 1.86 W cm⁻² and 54 mA cm⁻² at 0.9 ViR-free in a H2-O2 fuel cells at 80 °C. Our findings highlight the critical role of interface microenvironment regulation.