Csaba Janáky

• PhD
• Head of Department at University of Szeged

Replacing Ir with anode catalyst materials that are more abundant is a long-sought objective within the CO2 electrolysis community. The chemical environment (near-neutral pH, carbonate buffer electrolyte) that inherently develops during long-term operation, however, limits the pool of applicable candidates. In this contribution, Ir was replaced wit...

Hydrogen is expected to play an important role in decarbonizing different heavy industries and the transportation sector. Water electrolysis is, therefore, one of the most rapidly spreading energy technologies, with PEM electrolyzers taking a continuously increasing share in the technology mix. Most often, the aim is to form green hydrogen, utilizi...

Low‐dimensional copper halides with perovskite–analogue structure are a rapidly growing material family for light‐emitting and X‐ray screening devices. Among them Cs3Cu2I5 exhibits exceptional optoelectronic properties (large Stokes shift, high emission yield), due to the strong confinement effect of its 0D structure. However, its radioluminescence...

Ternary cesium-copper halide pseudo-perovskites are an emerging class of semiconductors in the field of optoelectronics. Similarly, to metal-halide perovskites, by controlling the halide-composition, their emission properties can be fine-tuned. Here...

This study demonstrates the electrochemical reduction of carbon monoxide (COR) at high current densities in a zero‐gap electrolyzer cell and cell stack. By systematically optimizing both the commercially available membrane electrode assembly components (including binder content and gas diffusion layer) and the operating conditions, we could perform...

Korunk társadalmának aktuális, az emberi életet döntően befolyásoló feladatai közé tartozik a levegőben felhalmozódott szén-dioxid koncentrációjának csökkentése. Erre megoldásként szolgálhat a szén-dioxid elektrokémiai reduk ciója, amelyet különböző pontforrásokon alkalmazva csökkenthető a légkörbe jutó szén-dioxid mennyisége. A Szegedi Tudományegy...

The importance of developing efficient technologies for converting solar energy into chemical energy has drawn attention, particularly through solar water splitting using photocatalytic materials. It highlighted the complexity of factors affecting the performance of photoelectrodes in this process, including bandgap energy, carrier density, morphol...

The ongoing energy transition will require a number of emerging technological concepts (e.g. Power-to-X and Hydrogen Economy, etc.) which will ultimately combine renewable energy, novel chemical production/conversion processes and innovative, integrated devices/systems to produce sustainable platform molecules, fuels and materials. In this book, re...

Membrane electrode assemblies (MEAs) are the key components of zero-gap CO 2 electrolyzers, having various functions in the electrolysis process. The catalyst layers serve as the reaction interface, the porous transport layers ensure reactant and product transport to and from the catalysts, while the membrane is responsible for the ion transport be...

One of the most important challenge of humanity in the mid-21st century is to maintain economic growth in an environmentally sustainable way. The European Green Deal addresses this issue, and it aims at making Europe climate neutral by 2050. To reach this aim, a promising technology is to convert a greenhouse gas, carbon dioxide into valuable chemi...

Understanding photophysical processes in lead halide perovskites is an important aspect of optimizing the performance of optoelectronic devices. The determination of exact charge carrier extraction rate constants remains elusive, as there is a large and persistent discrepancy in the reported absolute values. In this review, we concentrate on experi...

Despite the considerable efforts made by the community, the high operation cell voltage of CO2 electrolyzers is still to be decreased to move toward commercialization. This is mostly due to the high energy need of the oxygen evolution reaction (OER), which is the most often used anodic pair for CO2 reduction. In this study, OER was replaced by the...

Photoelectrochemistry holds the promise of directly converting sunlight to valuable chemical products. Photoelectrochemical (PEC) methods, however, lag behind their electrochemical counterparts in terms of current density. In this work, we demonstrate that, by using concentrated sunlight, we can achieve current densities similar to electrochemical...

The kinetics of electron extraction at the electron transfer layer/perovskite interface strongly affects the efficiency of a perovskite solar cell. By combining transient absorption and time-resolved photoluminescence spectroscopy, the electron extraction process between FA0.83Cs0.17Pb(I0.83Br0.17)3 and TiO2 single crystals with different orientati...

Photoelectrodes with FTO/Au/Sb2Se3/TiO2/Au architecture were studied in photoelectrochemical CO2 reduction reaction (PEC CO2RR). The preparation is based on a simple spin coating technique, where nanorod-like structures were obtained for Sb2Se3, as confirmed by SEM images. A thin conformal layer of TiO2 was coated on the Sb2Se3 nanorods via ALD, wh...

The production of syngas (i.e., a mixture of CO and H2) via the electrochemical reduction of CO2 and water can contribute to the green transition of various industrial sectors. Here we provide a joint academic–industrial perspective on the key technical and economical differences of the concurrent (i.e., CO and H2 are generated in the same electrol...

Thanks to the intense scientific interest, the field of CO 2 electrolysis witnessed remarkable progress (industrially relevant partial current densities, selective electrocatalysts towards small molecule products, multi-cell stacks, etc.) in the past decade. However, despite all these efforts, the energy efficiency of CO 2 electrolyzers is still re...

One of the most urgent challenges of our society is the continuously rising level of CO 2 in the atmosphere, caused by anthropogenic emission, including different point sources (e.g., cement factories, automobiles, airplanes). The electrochemical CO 2 reduction reaction (CO 2 RR) can be an alternative route for the chemical- and energy industries t...

Electrochemical CO reduction (ECOR) can act as a potential bridge between CO 2 -to-CO technologies and renewable production of C 2+ chemicals. Copper has been the most widely studied cathode catalyst for ECOR because of its unique ability to produce multicarbon products. Iridium and nickel are the most-widely used anode materials for acidic and alk...

Conversion of solar energy to valuable chemicals by using photoelectrochemical (PEC) techniques such as water splitting, carbon dioxide reduction reaction (CO 2 RR) and nitrogen reduction reaction (N 2 RR), are promising methods to solve the issues of energy crisis and global warming [1-2]. Two-dimensional (2D) and layered semiconductors, for examp...

Carbon monoxide is already an important raw material for the synthesis of different bulk chemicals (e.g., phosgene and different products thereof). Considering that it can be a building block for the synthesis of virtually any organic compound, carbon monoxide might play an important role in the production of synthetic fuels and other typical petro...

2D transition metal dichalcogenides are an attractive family of materials in the field of electronics and optoelectronics. They are excellent candidates for sensitive photodetectors, light harvesting devices (photovoltaics, photocatalysts or photoelectrodes), lasers or non-linear optical devices. All these applications rely on light-matter interact...

Photoelectrodes with architecture FTO/Au/Sb 2 Se 3 /TiO 2 for solar hydrogen evolution reactions (HER) and CO 2 reduction reactions (CO2RR) were studied. The fabrication followed a simple spin-coating technique whereby nanorod-like structures were obtained for the Sb 2 Se 3 as shown in the SEM images. A layer of TiO 2 was deposited via ALD which ac...

Electrochemical energy conversion devices are considered key in reducing CO2 emissions and significant efforts are being applied to accelerate device development. Unlike other technologies, low temperature electrolyzers have the ability to directly convert CO2 into a range of value‐added chemicals. To make them commercially viable, however, device...

To reach industrially relevant current densities in the electrochemical reduction of carbon dioxide, this process must be performed in continuous-flow electrolyzer cells, applying gas diffusion electrodes. Beyond the chemical composition of the catalyst, both its morphology and the overall structure of the catalyst layer are decisive in terms of re...

The persulfate-based advanced oxidation process is a promising method for degrading organic pollutants. Herein, TiO2 and ZnO photocatalysts were combined with the peroxydisulfate ion (PDS) to enhance the efficiency. ZnO was significantly more efficient in PDS conversion and SO4•− generation than TiO2. For ZnO, the PDS increased the transformation r...

Ternary copper halide pseudo‐perovskites are in the forefront of research as potential active materials in light emission applications. The optoelectronic properties of these compounds can be fine‐tuned by the preparation of mixed‐halide compositions. After irradiation, self‐trapped excitonic states are formed in these materials. However, the emiss...

Electrochemical energy conversion devices are considered key in reducing CO2 emissions and significant efforts are being applied to accelerate device development. Unlike other technologies, low temperature electrolyzers have the ability to directly convert CO2 into a range of value‐added chemicals. To make them commercially viable, however, device...

Magnesium vanadate (MgV2O6) and its alloys with copper vanadate were synthesized via the solution combustion technique. Phase purity and solid solution formation were confirmed by a variety of experimental techniques, supported by electronic structure simulations based on density functional theory (DFT). Powder X-ray diffraction combined with Rietv...

We demonstrate a two-step electrosynthesis approach for the preparation of silver pyrovanadate, Ag4V2O7 in thin-film form. In the first, cathodic step, polycrystalline Ag was deposited on fluorine doped tin oxide substrate from a non-aqueous bath. Aqueous pyrovanadate species were then generated by aging of a CO2-infused sodium orthovanadate (Na3VO...

Two-dimensional (2D) materials have unique band structure and show a great promise for optoelectronic and solar energy harvesting applications. Photoelectrochemical (PEC) processes are intensively studied employing these materials, due to their high specific surface area, and the possibility of surface modification by defect engineering/catalyst de...

Electrocatalytic CO 2 reduction reaction (CO 2 RR) in membrane electrode assembly (MEA) systems is a promising technology. Gaseous CO 2 can be directly transported to the cathode catalyst layer, leading to enhanced reaction rate. Meanwhile, there is no liquid electrolyte between the cathode and the anode, which can help to improve the energy effici...

While CO can already be produced at industrially relevant current densities via CO2 electrolysis, the selective formation of C2+ products seems challenging. CO electrolysis, in principle, can overcome this barrier, hence forming valuable chemicals from CO2 in two steps. Here we demonstrate that a mass-produced, commercially available polymeric pore...

Certain industrially relevant performance metrics of CO2 electrolyzers have already been approached in recent years. The energy efficiency of CO2 electrolyzers, however, is yet to be improved, and the reasons behind performance fading must be uncovered. The performance of the electrolyzer cells is strongly affected by their components, among which...

The performance of continuous-flow CO2 electrolyzers has substantially increased in recent years, achieving current density and selectivity (particularly for CO production) meeting the industrial targets. Further improvement is, however, necessary in terms of stability and energy efficiency, as well as in high-value multicarbon product formation. A...

Alpha‐Particle Detections In article number 2206645, Csaba Janáky, Mátyás Hunyadi, and coworkers demonstrate the spectroscopic detection of charged particles with cesium copper halide thin films. This study shows the first use of inorganic thin‐film scintillators with optical pulse characteristics and light yield competitive with doped single cryst...

Photoelectrochemical (PEC) hydrogen evolution reaction (HER) was studied on exfoliated, pristine and Pt‐decorated tungsten diselenide (p‐WSe2) nanoflake samples, using a previously developed microdroplet PEC microscopy approach. The WSe2 nanoflakes had well‐defined thicknesses as measured by atomic force microscopy, and the Pt nanoparticles (NPs) w...

N-doped carbon (N-C) materials are increasingly popular in different electrochemical and catalytic applications. Due to the structural and stoichiometric diversity of these materials, however, the role of different functional moieties is still controversial. We have synthesized a set of N-C catalysts, with identical morphologies (∼27 nm pore size)....

The cost and energy efficiency of photo-electrochemical devices require improvement to reach the market. In article number 2200585 Sophia Haussener and co-workers use highly concentrated sunlight to provide a concentrated photon flux, drastically reduce material needs and create a heat source that accelerates electrochemical reactions. This strateg...

Space chemistry is an emerging field, i.e., performing chemistry in space as distinguished from astrochemistry or planetary chemistry. First, our chapter discusses the unique properties (microgravity, low temperature, cosmic ray) of space, pointing out the extraordinary chemistry opportunities. Furthermore, the radical expansion of space industry i...

Photo‐electrochemical production of solar fuels from carbon dioxide, water, and sunlight is an appealing approach. Nevertheless, it remains challenging to scale despite encouraging demonstrations at low power input. Higher current densities require notable voltage input as ohmic losses and activation overpotentials become more significant, resultin...

Achieving high-efficiency photocatalytic conversion of CO2 into value-added chemicals remains a challenge. This study synthesizes In-doped TiO2 and g-C3N4 composites (In-TiO2/g-C3N4) via a facile and reliable method. The as-synthesized In-TiO2/g-C3N4 produces CO, CH4, and C2H4 under UV, and CO and CH4 under visible light from gaseous CO2 and H2O va...

We demonstrate the dynamic operation of CO2 electrolyzer cells, with a power input mimicking the output of a solar photovoltaic power plant. The zero-gap design ensured efficient intermittent operation for a week, while avoiding significant performance loss.

The field of electrochemical carbon dioxide reduction has developed rapidly during recent years. At the same time, the role of the anodic half-reaction has received considerably less attention. In this Perspective, we scrutinize the reports on the best-performing CO2 electrolyzer cells from the past 5 years, to shed light on the role of the anodic...

Lead halide perovskites (LHPs) have emerged as perspective materials for light harvesting, due to their tunable band gap and optoelectronic properties. Photocatalytic and photoelectrochemical (PEC) studies, employing LHP/liquid junctions, are evolving, where sacrificial reagents are often used. In this study, we found that a frequently applied elec...

A major goal within the CO2 electrolysis community is to replace the generally used Ir anode catalyst with a more abundant material, which is stable and active for water oxidation under process conditions. Ni is widely applied in alkaline water electrolysis, and it has been considered as a potential anode catalyst in CO2 electrolysis. Here we compa...

The recent coronavirus pandemic pointed out the vulnerability of humanity to new emerging infectious diseases. Experts warn that future pandemics may emerge more frequently with greater devastating effects on population health and the world economy. Although viruses are unable to propagate on lifeless surfaces, they can retain their infectivity and...

Titanium dioxide (TiO2) is often employed as a light absorber, electron-transporting material and catalyst in different energy and environmental applications. Heat treatment in a hydrogen atmosphere generates black TiO2 (b-TiO2), allowing better absorption of visible light, which placed this material in the forefront of research. At the same time,...

Visible light irradiation of a mixed halide perovskite (with bromide and iodide in the X-site) in contact with a solvent like dichloromethane (DCM) leads to selective expulsion of iodide from the film. This causes a concurrent blue-shift in band edge. We find that addition of Cs to A-site reduces the mobility of iodide ions under photoirradiation....

Continuous-flow electrolysers allow CO2 reduction at industrially relevant rates, but long-term operation is still challenging. One reason for this is the formation of precipitates in the porous cathode from the alkaline electrolyte and the CO2 feed. Here we show that while precipitate formation is detrimental for the long-term stability, the prese...

The exfoliation of layered materials into two-dimensional (2D) semiconductors creates new structural domains, for example, basal planes, defect-rich in-planes, and edge sites. These surface species affect the photoelectrochemical (PEC) performance, which in turn determines their applicability in solar energy conversion technologies. In this study,...

Studying the effect of nanoscale morphology on the photoelectrochemical performance of semiconductor electrodes has been in the forefront of research for over a decade, there are still major inconsistencies and controversies in the literature. Here we aimed to resolve some of these issues, by the controlled preparation of TiO2 photoelectrodes from...

Metal–halide perovskites transformed optoelectronics research and development during the past decade. They have also gained a foothold in photocatalytic and photoelectrochemical processes recently, but their sensitivity to the most commonly applied solvents and electrolytes together with their susceptibility to photocorrosion hinders such applicati...

Electrochemical reduction of CO 2 is a promising method for converting a greenhouse gas into value-added products, utilizing renewable energy. Novel catalysts, electrode assemblies, and cell configurations are all necessary to achieve economically appealing performance. In this talk, I am going to present a zero gap electrolyzer cell, which convert...

A new anion exchange membrane (PiperION) in conjunction with a tailored zero-gap electrolyzer cell allows unprecedented partial current densities.

Solar light–driven photoelectrochemical conversion of nitrate ions to nitrite is achieved on copper‐lead iodide nanocomposite electrodes. By optimizing the composition, 1.2 ± 0.05 mA cm⁻² photocurrent density is obtained under concentrated solar irradiation. The reduction products are NO2⁻ and N2, at 0.61 V reversible hydrogen electrode (RHE), whic...

Interest in silver-based semiconductors dates to the early years of analog photography. On the other hand, the recent discovery of new silver oxide-based ternary semiconductors has caused a resurgence of interest in these compounds for new technologies. In this vein, the present study provides a counter example to the two perennial issues confronti...

Water oxidation (i.e., oxygen evolution) reaction is the most often used, green anodic pair of carbon dioxide (CO2) electroreduction, mimicking the natural photosynthetic process. At the same time, it requires high energy input, and generates a product of little commercial value (i.e., oxygen). Finding appropriate alternative anode processes to be...

In this study, the photoelectrochemical behavior of electrodeposited FeNiOOH/Fe2O3/graphene nanohybrid electrodes is investigated, which has precisely controlled structure and composition. The photoelectrode assembly is designed in a bioinspired manner where each component has its own function: Fe2O3 is responsible for the absorption of light, the...

Visible light irradiation of the mixed halide perovskite film in contact with a solvent (dichloromethane, DCM) in which the film otherwise is stable, leads to selective expulsion of iodide (I) from the film with concurrent shift in the band edge to lower wavelengths. We have now employed mixed halide perovskites to uncover the influence of A-site c...

Electrochemical reduction of CO 2 is a promising method for converting a greenhouse gas into value-added products, utilizing renewable energy. Novel catalysts, electrode assemblies, and cell configurations are all necessary to achieve economically appealing performance. In this talk, I am going to present a zero gap electrolyzer cell, which convert...

In this talk, I am going to present how electrodeposition allows the synthesis of complex photoelectrode architectures with precisely controlled structure and composition. The presented photoelectrode assembly follows a bioinspired design, where the different components have different function. Fe 2 O 3 was responsible for light absorption, the gra...

Bimetallic nanoparticles (NPs) offer great flexibility to tailor the activity and selectivity in electrocatalytic conversion of carbon dioxide (CO 2 ) to valuable chemicals. Here, we report on the electrocatalytic behavior of Au-Sn, Au-Ag and Au-Pb NPs, to highlight the effect of the intermetallic phase formation and the bimetallic composition in C...

The electrochemical conversion of carbon dioxide (CO2) to high-value chemicals is an attractive approach to create an artificial carbon cycle. Tuning the activity and product selectivity while maintaining long-term stability, however, remains a significant challenge. Here, we study a series of Au–Pb bimetallic electrocatalysts with different Au/Pb...

According to the currently accepted structure-property relationships, aceno-pentalenes with angular shape (fused to the 1,2-bond of the acene) exhibit higher antiaromaticity than those with linear shape (fused to the 2,3-bond of the acene). To explore and expand the current view, we designed and synthesized molecules where two isomeric, yet, differ...

According to the currently accepted structure-property relationships, aceno-pentalenes with angular shape (fused to the 1,2-bond of the acene) exhibit higher antiaromaticity than those with linear shape (fused to the 2,3-bond of the acene). To explore and expand the current view, we designed and synthesized molecules where two isomeric, yet, differ...

Electrochemical reduction of CO2 is a value-added approach to both decrease the atmospheric emission of carbon-dioxide and to form valuable chemicals. We present a zero gap electrolyzer cell, which continuously converts gas phase CO2 to products without using any liquid catholyte. This is the first report of a multi-layer CO2 electrolyzer stack for...

Halide ion mobility in metal halide perovskites remains an intriguing phenomenon, influencing their optical and photovoltaic properties. Selective injection of holes through electrochemical anodic bias has allowed us to probe the effect of hole trapping at iodide (0.9 V) and bromide (1.15 V) in mixed halide perovskite (CH3NH3PbBr1.5I1.5) films. Upo...

The electrocatalytic reduction of carbon dioxide (CO 2 )on Au–Ag bimetallic alloy nanoparticles was scrutinized. This system provides a good model to investigate the correlation between the electrocatalytic activity and the composition of the nanoparticles. The CO Faradaic efficiency (and thus the forming CO:H 2 ratio)was changed linearly by contro...

The morphology of electrode materials is often overlooked when comparing different carbon-based electrocatalysts for carbon dioxide reduction. To investigate the role of morphological attributes, we studied polymer-derived, interconnected, N-doped carbon structures with uniformly sized meso or macropores, differing only in the pore size. We found t...

Semiconducting materials are essential building blocks of the majority of devices in the 21 st century. The ability of semiconductors to generate charge carriers under band gap irradiation makes them suitable for a myriad of applications (e.g., solar cells, photocatalysts, photodetectors). In recent years the emergence of organic-inorganic lead hal...

One of the most critical challenges of the 21 st century is the shift in energy use from fossil fuels to renewable sources. Photoelectrochemical solar energy conversion, as a potentially attractive candidate, has gained an increased momentum during the recent years. Although both water-splitting (hydrogen evolution) and carbon dioxide reduction are...

Layered transition metal dichalcogenides (TMDCs) have become promising candidates for photoelectrochemical (PEC) studies from the 80’s. Both n- and p-type MoSe 2 , and WSe 2 materials were studied in photoelectrocatalytic reactions using model redox couples and hydrogen evolution reaction. (1-2) Exfoliation of the bulk, layered crystals to single-...

This study focuses on a solid solution series, Ca(La 1-x Ce x ) 2 S 4 (0 ≤ x ≤ 1), where the f electron density is absent in CaLa 2 S 4 and is progressively increased until it is maximized in CaCe 2 S 4 . Correspondingly, these samples, synthesized by a sealed ampule method, showed progressive variations in color ranging from gray for CaLa 2 S 4 to...

Solution combustion synthesis (SCS) is shown to be versatile for the rapid-one-pot synthesis of three compounds and four polymorphs in the Cu-V-O ternary family: α-CuV2O6, α- and β-Cu2V2O7, and γ-Cu3V2O8. These compounds feature copper: vanadium stoichiometric ratios ranging from 1:1 to 3:1; their structural, electronic, optoelectronic, and photoel...

Nickel oxide (NiO) is often used as a hole-transporter material in both photovoltaic and photoelectrochemical solar cells. As a result of the reversible nickel(II)/(III) transformation, it is also electrochromic. These potential-dependent optoelectronic properties of this intriguing material, however, are yet to be fully understood. In this article...

Owing to its high hole conductivity and ease of preparation, CuI is among the inorganic hole transporting materials that were introduced early on in metal halide perovskite solar cells, but its full potential as a semiconductor material is still to be realized. We have now performed ultrafast spectroelectrochemical experiments on ITO/CuI electrodes...