Direct solar-driven hydrogen production provides a sustainable route to storing renewable energy in chemical bonds, but practical deployment requires photoelectrodes that combine high efficiency, long-term stability, and scalable fabrication. This presentation describes our recent advances in integrated photovoltaic (photo)electrodes based on organic bulk heterojunctions and halide perovskites for unassisted solar hydrogen production. We demonstrate monolithic organic tandem integrated photovoltaic anodes employing tandem PTQ11:GS-ISO and PTQ10:L8-BO absorbers of high photovoltage and stability together with engineered graphite/Ni/NiFeOOH catalytic sheets that simultaneously improve charge extraction, oxygen evolution kinetics, and operational stability. The optimized tandem (photo)anodes deliver sufficient photovoltage for unassisted, bias-free water splitting, achieving solar-to-hydrogen efficiencies of 8.4% and stable operation for over 67 h. On the (photo)cathode side, we demonstrate advances in halide perovskite integrated photovoltaic (photo)cathodes that combine Rb_0.05Cs_0.05MA_0.05FA_0.85Pb(I_0.95Br_0.05)₃ photovoltaics with graphite protection layers and Pt nanoparticles grown on ZIF-8-derived porous carbon, reducing precious-metal loading by an order of magnitude while maintaining excellent hydrogen evolution activity and continuous operation exceeding 160 h in acidic electrolyte. Together, these studies establish practical design principles for integrating high-performance photovoltaic absorbers, conductive protective interfaces, and efficient electrocatalysts, providing a scalable pathway towards durable and efficient solar fuel production using next-generation solar-drive electrochemical devices.

Direct solar-driven conversion of carbon dioxide to chemicals and fuels requires identification of efficient, durable, and selective photocathodes. The Materials Project identified a number of candidates.[1] Since then, we have synthesized and investigated a number of II-VI, III-VI, and I-III-VI chalcogenide semiconductors and investigated them as photocathodes for CO₂ reduction, in particular their selectivity and durability. We have demonstrated that for the wide bandgap CuGa₃Se₅ chalcopyrite absorber coated with a CdS buffer layer selectivity and durability are well addressed by an organic coating generated in situ from an N,N′-(1,4-phenylene)bispyridinium ditriflate salt in the electrolyte.[2] The molecular additive provides a 30-fold increase in selectivity toward CO₂R products compared to the unmodified system and lowers Cd corrosion at least 10-fold. This dual functionality highlights the promise of hybrid solid-state-molecular photocathodes for enabling durable and efficient solar fuel systems. Other photocathodes we have reported include ZnTe and ZnGa₂Te₄.[3,4] This presentation will highlight the variations in product selectivity and durability observed for different combinations of deposition conditions, post-growth treatments, and coatings derived from molecular precursors in the electrolyte for several photocathodes.

Photoelectrochemical (PEC) water oxidation offers a promising route for solar fuel production, yet its efficiency remains critically limited by the sluggish kinetics of the anodic oxygen evolution reaction (OER) [1,2]. BiVO₄ is among the most studied photoanode materials due to its favorable bandgap and valence band position, but its practical performance is severely hindered by poor charge transport and surface recombination [3]. Here, we report a novel scalable fabrication strategy that, for the first time, combines the Autodrop process and automated spray coating for the sequential deposition of FePO₄ and Ti₃C₂Tₓ MXene overlayers onto BiVO₄ photoanodes. This two-step approach enables precise control over each functional layer while remaining fully compatible with large-scale production. The FePO₄ interlayer acts as a surface passivation and hole-transport layer [4], while the highly conductive MXene nanosheets serve as a co-catalytic interface and conductive bridge, collectively suppressing recombination and accelerating OER kinetics. Systematic optimization of MXene loading reveals a critical balance between MXene coverage and FePO₄ exposure, achieving an approximately 50% improvement in photocurrent density. Furthermore, the MXene overlayer enhances photoanode stability by facilitating continuous hole extraction and preventing BiVO₄ degradation under operating conditions. This work demonstrates a viable and reproducible route toward high-performance, stable photoanodes for solar fuel applications.

Photoelectrochemical (PEC) technologies provide a direct route for converting solar energy into fuels and value-added chemicals. While remarkable progress has been achieved in the development of photoelectrode materials, the transition from laboratory demonstrations to practical applications remains limited by challenges in scalable manufacturing, reactor engineering, long-term stability, and operation under realistic conditions. Advancing PEC technologies toward higher technology readiness levels therefore requires moving beyond the optimization of individual photoelectrodes toward the development of integrated systems designed for manufacturability, process intensification, and real-world deployment.

A first challenge is the scalable fabrication of photoelectrodes. Simply increasing electrode dimensions is insufficient because limitations associated with conductive substrates and charge transport rapidly compromise device performance. Industrially compatible manufacturing methods are therefore essential for producing reproducible photoelectrodes over large areas while minimizing material consumption and waste. Among the available approaches, screen printing represents a promising route for the fabrication of metal-oxide semiconductor photoanodes owing to its scalability, versatility, compatibility with large-area substrates, and potential for industrial implementation.

As PEC devices increase in size, reactor engineering becomes equally important for controlling light distribution, mass transport, electrical losses, electrode configuration, and product separation. Modular reactor architectures based on segmented photoelectrodes offer an attractive strategy for overcoming the limitations associated with monolithic large-area electrodes while enabling flexible electrical configurations and progressive scale-up. Such designs also facilitate coupling with solar concentrators and outdoor operation, providing a realistic pathway toward intensified solar chemical production.

Beyond materials and reactor design, improving the technical and economic viability of PEC technologies also requires reaction engineering and operation under realistic conditions. Current strategies include replacing the oxygen evolution reaction with more valuable oxidation processes, coupling photoanodes with selective reduction reactions to maximize overall process value, integrating photoelectrochemical and bioelectrochemical systems to exploit their complementary operating windows, and operating under concentrated sunlight to increase solar-to-chemical productivity. Together, these approaches broaden the application space of PEC technologies while improving their overall efficiency and sustainability.

Overall, this contribution presents systems-level strategies for advancing photoelectrochemical technologies beyond laboratory-scale demonstrations. By integrating scalable photoelectrode manufacturing, modular reactor engineering, alternative reaction pathways, hybrid photo(bio)electrochemical systems, and operation under realistic solar conditions, the work illustrates how materials science, device engineering, and process design can be combined to accelerate the transition of PEC technologies toward practical solar-driven chemical production. The examples presented are drawn from complementary developments carried out within the DISTECH2, PHOENIX, and ALGAESOL projects, highlighting a common strategy for advancing PEC systems from fundamental materials to integrated technologies with higher technology readiness levels.

The direct conversion of solar energy into chemical fuels represents one of the most promising strategies for achieving a sustainable energy future. Among the emerging classes of photocatalysts, metal halides perovskites and perovskite inspired materials have recently attracted considerable attention owing to their outstanding optoelectronic properties, compositional versatility, and the possibility of tailoring their electronic structure through rational materials engineering. Nevertheless, their practical implementation in solar fuel generation still requires a deeper understanding of the relationship between composition, crystal structure, charge-carrier dynamics, and catalytic activity. This contribution will discuss recent advances in the design of metal halides for solar-driven hydrogen and ammonia production, highlighting how compositional engineering, dimensionality control, alloying strategies, defect chemistry, and heterostructure design can be exploited to optimize visible-light absorption, charge separation, and interfacial reaction kinetics. Particular attention will be devoted to lead-free perovskite-inspired materials based on Bi- and Sb-halides, whose electronic structure can be tuned through metal alloying to achieve significantly reduced band gaps while preserving their intrinsic chemical stability. The role of scalable vapor-phase deposition techniques for producing high-quality thin films and model systems for mechanistic investigations will also be discussed. Beyond materials development, emphasis will be placed on the mechanistic understanding of photocatalytic processes, combining advanced structural and spectroscopic characterization with activity studies to identify the key factors governing charge generation, transport, and surface reaction pathways. These insights provide fundamental design principles for the development of next-generation metal halide photocatalysts and contribute to establishing a rational framework for the realization of efficient, stable, and sustainable solar fuel technologies.

Photocatalytic CO₂-to-CO conversion is a promising route toward solar fuel production and carbon-neutral chemical manufacturing. One strategy to improve the efficiency of molecular photocatalytic systems is the integration of a selective CO₂ reduction catalyst with a photosensitiser capable of harvesting a broad range of the solar spectrum. Conjugated covalent linkage of the catalyst and photosensitiser into a molecular assembly can facilitate intramolecular electron transfer and enhance overall photocatalytic performance.

Here, we combine the well-established catalyst Re(CO)₃(bpy)Cl with BODIPY-based photosensitizers. Meso-substitution of BODIPY with phenyl (Ph), anthracene (An), or phenyl-anthracene (Ph-An) groups induces spin-orbit charge-transfer intersystem crossing, resulting in efficient triplet-state formation with triplet quantum yields following the trend Ph-An > An > Ph. [1,2] These long-lived triplet states can be reduced by a sacrificial electron donor to generate BODIPY radical anions, which subsequently transfer electrons to the catalytic center. In bimolecular photocatalytic systems, this enhances CO₂ reduction activity, with photocatalytic performance following the same trend. [2] However, the kinetics of the bimolecular photocatalytic reaction depends on stochastic encounters and charge transfer between the two components, which limits the overall activity.

To force the photosensitiser and catalytic center into close contact, we designed and synthesized a series of novel rhenium–BODIPY supramolecular assemblies in which a bipyridine ligand is bound to a meso-substituted BODIPY through an ethylene linker at the α-position. This design provides close contact and conjugation between the photosensitizer and catalytic center. In addition to a comparison of the conjugated monomolecular system to the established bimolecular ones, the meso-substituents were systematically varied to study the influence of sterically hindered groups on the photophysical properties and photocatalytic activity of the supramolecular systems.

Compared with the best-performing bimolecular system, consisting of An-BODIPY and Re(CO)₃(bpy)Cl, the respective tethered assembly exhibited more than a sevenfold increase in CO production. Surprisingly, the supramolecular catalysts displayed a reversed activity trend relative to the corresponding intermolecular systems, with Ph-BODIPY-bpy-Re(CO)₃Cl emerging as the most active catalyst and achieving a turnover number (TON) exceeding 500 after 7 h of irradiation. These results indicate that Ph- and An/Ph-An-substituted assemblies operate through distinct photocatalytic pathways, revealing a new strategy for utilizing short-lived excited states in photocatalytic CO₂ reduction.

Solar energy conversion through photoelectrochemical (PEC) cells represents a promising route for sustainable fuel production, but achieving efficient and stable devices still requires significant advances in materials and interfacial engineering. While inorganic semiconductors such as metal oxides have been widely investigated due to their low cost, abundance, and stability, their performance is often limited by charge recombination, low carrier mobility, and restricted visible-light absorption. To overcome these limitations, our group explores several strategies, including surface modification, cocatalyst incorporation, and, more recently, the integration of organic semiconductors into hybrid photoelectrodes.

Among the different organic materials, conjugated porous polymers (CPPs) have emerged as particularly attractive candidates because they combine light-harvesting capability, charge transport properties, high surface area, and enhanced chemical stability. However, their application in photoelectrochemical systems has been hindered by the difficulty of processing these materials into high-quality thin films, as they are commonly synthesized as micron-sized particles. To address this challenge, we have developed different approaches for integrating CPPs into photoelectrodes, with special emphasis on nanostructuring and electropolymerization techniques.

In this work, two carbazole-based CPPs, p-BCzB and p-TCzB, were synthesized as ultrathin films through electropolymerization and incorporated into Cu₂O photocathodes as multifunctional interfacial layers. Hybrid architectures were prepared by positioning the polymer either beneath or on top of the Cu₂O layer, allowing the influence of interface design on charge-transfer processes to be investigated. All hybrid electrodes exhibited improved photoelectrochemical performance compared with bare Cu₂O, with photocurrent densities increasing by up to a factor of three. The best results were obtained when the polymer was deposited as an ultrathin overlayer, highlighting the importance of nanoscale interfacial engineering.

Electrochemical impedance spectroscopy and transient absorption spectroscopy revealed the multifunctional role of the CPPs within the hybrid structures. When located beneath Cu₂O, the polymers form heterojunctions that promote directional charge separation and facilitate carrier transport. In contrast, when deposited on top of the semiconductor, they act primarily as passivation layers, suppressing surface recombination and extending the lifetime of photogenerated charges. Among the studied materials, p-TCzB exhibited superior performance due to its more extended π-conjugated structure, which enhances charge delocalization and interfacial charge transfer.

These findings demonstrate that CPPs can simultaneously function as light-harvesting, charge-transport, and passivation layers, leading to improved photocurrents, enhanced charge-transfer kinetics, and longer carrier lifetimes. Beyond photoelectrochemical applications, this strategy opens new opportunities for incorporating conjugated porous polymers into a wide range of optoelectronic devices where efficient interfacial charge management and high-quality thin-film fabrication are essential.

Photoelectrochemical (PEC) water oxidation using semiconductor photoanodes represents a promising pathway for sustainable hydrogen production. However, accurately quantifying bulk transport, interfacial recombination, and charge-transfer kinetics remains a challenge due to the limitations of existing optoelectronic models. Many traditional frameworks, such as the widely used two-capacitor model, assume perfect electron extraction or fail to maintain self-consistency between steady-state and dynamic small-perturbation measurements. Furthermore, they often neglect the critical distinction between the internal quasi-Fermi-level splitting and the external applied voltage under illumination.

To resolve these issues, we present a comprehensive, self-consistent analytical model designed to interpret both steady-state current–voltage characteristics and small-perturbation responses across the time and frequency domains. The framework explicitly accounts for imperfect electron extraction at the collecting contact and links bulk recombination directly to the internal voltage profile. The physical validity of the analytical model is corroborated by full drift-diffusion simulations, demonstrating excellent agreement across varying light intensities and bias potentials.

Applying this model to experimental data for a hematite photoanode yields specific charge-transfer and extraction parameters near the 1 sun open-circuit potential. The framework, which links extraction velocity to electronic mobility, accounts for the characteristic linear dependence of photocurrent on voltage observed in hematite, offering a robust tool for analyzing diverse photoelectrochemical systems.

Bismuth vanadate (BiVO₄) is one of the most extensively investigated photoanodes for solar-driven water oxidation owing to its suitable bandgap, strong visible-light absorption, favourable band-edge alignment, and chemical stability. However, its photoelectrochemical (PEC) efficiency remains fundamentally limited by poor charge transport and severe electron–hole recombination. These limitations originate from intrinsically low carrier mobility and short diffusion lengths, which arise from the formation of self-trapped small polarons that strongly couple charge transport to local lattice distortions. Consequently, the photoactivity of BiVO₄ is exceptionally sensitive to atomic-scale structural perturbations, making it an ideal model system for exploring how local chemical environments influence macroscopic PEC function.

Transition-metal (TM) incorporation has emerged as a promising strategy to improve BiVO₄ performance through modification of its electronic structure, defect chemistry, and charge-transport pathways. However, despite numerous reports of enhanced photocurrents and improved charge-separation efficiencies, the microscopic origins of these improvements remain poorly understood. In particular, the relationship between TM coordination environment, electronic coupling with the host lattice, and the resulting charge-carrier dynamics has remained largely unresolved. Addressing this challenge requires correlating local structural information with electronic and photophysical behaviour across multiple length and time scales.

Here, we systematically investigate the influence of Fe, Co, and Ni incorporation on the structural, electronic, and PEC properties of BiVO₄ photoanodes. By combining synchrotron-based X-ray absorption spectroscopy (XAS), operando X-ray measurements, transient absorption spectroscopy spanning femtosecond-to-microsecond timescales, and electrochemical impedance spectroscopy, we establish direct structure–property relationships linking the local incorporation environment of transition metals to charge-separation dynamics and PEC performance.

All transition-metal-modified photoanodes exhibit enhanced water-oxidation activity compared with pristine BiVO4, following the performance trend Ni > Fe > Co > BiVO₄. However, our results reveal that these improvements originate from fundamentally different mechanisms. X-ray spectroscopic analysis demonstrates that Fe and Co are incorporated predominantly within heterogeneous oxide-like environments that remain only weakly electronically coupled to the surrounding BiVO₄ lattice. These environments introduce structural and electronic disorder, generating localized states that provide only limited improvements in charge separation and carrier extraction.

In contrast, Ni incorporation produces a markedly different local structure. Spectroscopic fingerprints reveal the formation of highly oxidized, locally octahedral Ni–O units that remain strongly integrated within the BiVO₄ framework. This incorporation induces persistent modifications of the surrounding V–O network, evidencing significant electronic communication between the dopant and host lattice. Rather than acting as isolated impurity centres, these Ni species alter the electronic landscape of BiVO₄ itself, leading to profound consequences for charge-carrier behaviour.

Ultrafast TAS measurements show that Ni incorporation substantially suppresses charge localisation and recombination from the earliest stages of photoexcitation. The resulting charge carriers exhibit significantly prolonged lifetimes across all measured temporal regimes, from femtoseconds to microseconds, indicating more efficient charge separation and enhanced carrier persistence. Operando X-ray absorption spectroscopy further demonstrates that lattice-incorporated Ni remains electronically active under working photoelectrochemical conditions, exhibiting dynamic changes in oxidation state associated with photogenerated charge accumulation. These observations directly connect the local electronic structure of the incorporated Ni species with the functional processes governing solar water oxidation.

Collectively, our findings demonstrate that the performance of transition-metal-modified BiVO₄ cannot be rationalized solely on the basis of dopant identity or nominal composition. Instead, the decisive factor is the nature of the electronic coupling established between the incorporated species and the host lattice. Strongly coupled incorporation environments, exemplified by Ni, fundamentally reshape charge-carrier dynamics and suppress recombination, whereas weakly coupled oxide-like environments yield only marginal benefits. This work provides new mechanistic insight into how local coordination chemistry governs photoelectrode function and establishes a general design principle for engineering next-generation oxide photoanodes for solar fuel production.

The exploitation of renewable energy sources (such as sunlight), striving to produce alternative fuels, is one of the most pursued strategies to relieve the global energy thirst. With this aim, a viable but challenging approach consists in the development of photoelectrochemical cells.[1] These devices mimic the natural photosynthesis by storing solar energy as chemical energy in value-added compounds produced at two separated electrodes.

In this contribution, we will report on Hematite photoanodes, prepared via hydrothermal synthesis in the presence of a Ti(IV) precursor belonging to the family of MXenes. The latter are two-dimensional materials with general formula M_n+1X_nT_x (where M is an early transition, X is C and/or N, and T is a terminal surface group), recently reported to improve the performances of perovskite solar cells by inducing the formation of an interface dipole and tuning the interfacial band alignment.[2] The structure of the MXene of choice, namely Ti₃C₂T_x, is reported in Figure.

The MXene-modified photoanodes showed a significant improvement in terms of photocurrent (up to 3.0 mA/cm² at 1.85 V vs RHE) when compared to Hematite electrodes not including such precursor in the synthetic route. Electrochemical Impedance Spectroscopy, Intensity Modulated Photocurrent Spectroscopy and Transient Absorption Spectroscopy are comparatively  applied to investigate the charge transfer dynamics transfer/transport in these modified photoanodes.  

The intermittent nature of solar energy necessitates efficient and scalable energy storage technologies to enable its widespread deployment. Solar Redox Flow Cells (SRFCs) are an emerging photoelectrochemical (PEC) technology that addresses integrates solar energy harvesting, storage, and on-demand electricity and heat generation within a single device [1]. Although significant advances have been reported in semiconductor photoelectrodes and redox chemistries, demonstrations at higher technology readiness levels remain limited [2]. This communication addresses key scientific and engineering challenges toward SRFC commercialization through the development of advanced materials and scalable device architectures. Device upscaling was initiated through the harmonization of experimental procedures and the design of a reproducible small-scale device – the UniFlow cell [3], followed by the development of the SolarFlow25 cell and its modular 100 cm2 photoactive-area architecture. Coupled with an optimized industry-grade silicon heterojunction (Si-HTJ) photoelectrode, the system achieves an unprecedented photocharging efficiency of ca. 11.58 % for a single-photoabsorber SRFC. These results demonstrate the feasibility of high-performance SRFCs using scalable, industry-compatible materials.

The surgent request for solar-based optoelectronics calls for a continuous improvement of technologies that combine solar conversion and energy storage, both in their performance and compactness. In this sense, doped Metal Oxide Nanocrystals (MO NCs) are exploitable as both photo-active and charge-storing layer in 2-terminal photocapacitors owing to photodoping. This phenomenon bestows MO NCs the ability of accumulating and retaining charges upon illumination¹. The spectroscopical changes detected under illumination for MO NCs solutions of several compounds, e.g., indium tin oxide (ITO) and substoichiometric tungsten oxide (WO_3-x), confirm the presence of electron accumulation². Consequently, we investigated the possibility of transferring these properties in solid state form. A solution processing approach was adopted to fabricate electrodes, with the goal of employing them as the photoactive element in 2-terminal photocapacitors³. The devices were fabricated with a simple architecture ensuring the possibility of studying the photostorage behavior of WO_2.69 and ITO under solar and UV illumination, respectively. Under illumination conditions, we detected an increment in the specific capacitance of the device. These promising results, along with the possibility of adding complexity to the device architecture via careful design of the counter electrode and other components, pave the way for the realization of a new generation of energy storage devices⁴.

Water purification is a present and future challenge for human development, as water is essential for life. Effluents from various industries release toxic and harmful substances, including dyes and nanoplastics, making effective water treatment methods crucial for environmental sustainability. Reactive oxygen species (ROS), such as such as hydroxyl radical (HO^⋅) and superoxide radical (O₂^⋅−), have the ability to oxidize and degrade contaminants. Thus, their generation is of significant interest in water purification technologies. Carbon-based materials exhibit electrochemical activity toward the oxygen reduction reaction (ORR), with selectivity for the two-electron pathway leading to hydrogen peroxide (H_₂O_₂). The decomposition of H_₂O_₂ and its intermediates results in the formation of ROS relevant to pollutant degradation. In this work, the electrochemical production ROS and the simultaneous degradation of dyes are investigated using carbon nano-onion (CNO) materials. Electrochemical analyses were performed in a three-electrode cell under neutral pH conditions. A range of applied potentials was studied, revealing optimal dye degradation at −0.2 V vs RHE and achieving complete Rhodamine B degradation after 240 minutes. These results highlight the potential of CNO materials as efficient and sustainable catalysts for advanced water treatment applications.

Hybrid AMX3 perovskites have in the last years revolutionized the scenario of photovoltaic technologies. We developed an effective GW method incorporating spin-orbit coupling [1] which allows us to accurately model the electronic, optical and transport properties of halide perovskites. In parallel, a series of different strategies will be reported to increase the device stability and efficiency.[2] While instability in aqueous environment has long impeded employment of metal halide perovskites for heterogeneous photocatalysis, recent reports have shown that some particular tin halide perovskites (THPs) can be water-stable and active in photocatalytic hydrogen production. To unravel the mechanistic details underlying the photocatalytic activity of THPs, we compare the reactivity of the water-stable and active DMASnBr3 (DMA = dimethylammonium) perovskite against prototypical MASnI3 and MASnBr3 compounds (MA = methylammonium), employing advanced electronic–structure calculations. We find that the binding energy of electron polarons at the surface of THPs, driven by the conduction band energetics, is cardinal for photocatalytic hydrogen reduction.[3] In this framework, the interplay between the A-site cation and halogen is found to play a key role in defining the photoreactivity of the material by tuning the perovskite electronic energy levels. Our study, by elucidating the key steps of the reaction, may assist the development of more stable and efficient materials for photocatalytic hydrogen reduction. We report a report is made on a composite system including a double perovskite, used for solar-driven hydrogen generation and nitrogen reduction, quantified by a rigorous analytical approach. [4] Finally, a new approach for enantioselective synthesis has been reported with chiral perovskite catalyst.

Efficient conversion and storage of solar energy are crucial steps in the establishment of a renewable and carbon neutral energy supply. Photoelectrochemical (PEC) water splitting is a promising energy conversion and storage technology, considered very promising to make use of the large amounts of sunlight that reach the surface of earth. It renders the direct conversion of light into chemical energy possible, e.g. solar fuels like hydrogen or ammonia. By the aid of nanostructuring, diffusion pathways can be drastically shortened in case of low charge carrier diffusion lengths.

In recent years, earth-abundant Fe-based materials like spinel ferrites have emerged as auspicious materials for PEC. They have the inherent ability to absorb a large part of the visible light spectrum with band gaps around 2 eV, while some of them being also very good electrocatalysts. In this presentation, the activity and stability of both pristine and hydrogen-treated ZnFe₂O₄ will be presented.[1] Using an illuminated scanning flow cell setup, we monitored the activity and dissolution rates of ZnFe₂O₄ under operando PEC conditions. It was found that at PEC water oxidation conditions, ZnFe₂O₄ does not degrade in basic pH. Moreover, thermally reduced ZnFe₂O₄ shows expected higher OER activity without compromising the stability compared to the pristine one.

Due to its high electric conductivity, beneficial hole diffusion length, and band gap of 2.7 eV suitable to absorb visible light, WO₃ is a well-understood photoanode for photoelectrochemical water splitting.[2,3] In this contribution, a study to unravel the influence of seed layers on the performance of hydrothermally-grown WO₃ photonanodes will be presented.[4] Moreover, using a sol-gel synthesis method adapted from Hillard et al.,[5] we systematically investigated the influence of calcination temperature, film thickness, and porosity on the structural, optical, and electronic properties of WO₃ thin films,[6] reaching photocurrent exceeding 3.7 mA cm^-2.[7] Finally, the application of mesoporous WO₃ photoanodes for photoelectrochemical HMF oxidation will be presented.[8]

AgBiS2 is a narrow-band-gap, water-stable semiconductor with strong visible-light absorption, making it a promising absorber material in devices for solar-driven photoelectrocatalysis (PEC)^[1,2]. Although its photovoltaic properties have been widely studied, the influence of cation disorder on PEC performance remains largely unexplored^[3,4]. Solvothermally synthesized AgBiS₂ nanoparticles were processed in photoanode thin films via ultrasonic spray coating. A combination of X-ray diffraction and spectroscopic analyses reveal how thermal annealing partially homogenizes the cation distribution, showing lattice contraction and subtle band-structure tuning toward a slightly n-type behavior. The annealed electrodes exhibit higher photocurrents for water oxidation and increased donor density. The improved performance was also observed in a hole scavenger solution, which was employed to thoroughly characterize the behavior of the photoanodes: impedance spectroscopy suggests enhanced hole flux to the semiconductor/electrolyte interface, while transient absorption spectroscopy identifies sub-bandgap trap-mediated recombination as the primary limitation of the photoanode’s performance. These results support the implementation of AgBiS₂ as low band gap absorber in electrode architectures and suggest its use with fast redox mediators for selective photooxidation for sustainable solar energy conversion as a promising application.