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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, a post-synthetic halide exchange method was employed to alter the halide-composition and thus the emission properties of polycrystalline Cs 3 Cu 2 Br 5 layers.

Cu₂SnSe₃ (CTSe) shows promise due to its wide solar absorption and tunable band gap, though low efficiency caused by interface recombination and crystallinity issues remains a challenge. In this study, a systematic and facile synthesis method for CTSe nanoparticles (NPs) is demonstrated, accompanied by an in-depth analysis of their growth mechanisms. A comprehensive experimental and theoretical investigation is conducted to explore the structural, compositional, optoelectronic, and band alignment properties of p-type CTSe NPs as a solar absorber, along with n-type CdSe and ZnSe NPs as buffer layers. Additionally, the band edge positions of the synthesized NPs are estimated using cyclic voltammetry (CV), UV photoelectron spectroscopy (UPS), and density functional theory (DFT), enabling the modulation of band offsets through interface engineering. The investigation revealed a staggered type-II band alignment at the CTSe/CdSe heterojunction, characterized by a minimal conduction band offset (CBO) of 0.06 eV. The findings from CV and UPS measurement supported by density functional theory-based calculations, suggests effective charge carrier separation and transport at the interface. The CTSe/CdSe heterojunction exhibited Schottky I-V characteristics, demonstrating a current of 1 mA in dark conditions. These findings demonstrate CTSe NPs' potential as an efficient absorber in thin-film solar cells, addressing interface recombination losses and improving performance., (© 2025 Wiley‐VCH GmbH.)

Electrochemical reduction of carbon monoxide offers a possible route to produce valuable chemicals (such as acetate, ethanol or ethylene) from CO 2 in two consecutive electrochemical reactions. Such deeply reduced products are formed via the transfer of 4-6 electrons per CO molecule. Assuming similar-sized CO 2 and CO electrolyzers, 2-3-times larger current densities are required in the latter case to match the molar fluxes. Such high reaction rates can be ensured by tailoring the structure of the gas diffusion electrodes. Here, the structure of the cathode catalyst layer was systematically varied using different polymeric binders to achieve high reaction rates. Simple linear polymers, bearing the same backbone but different functional groups were compared to highlight the role of different structural motifs. The comparison was also extended to simple linear, partially fluorinated polymers. Interestingly, in some cases similar results were obtained as with the current state-of-the-art binders. Using different surface-wetting characterization techniques, we show that the hydrophobicity of the catalyst layer-provided by the binder- is a prerequisite for high-rate CO electrolysis. The validity of this notion was demonstrated by performing CO electrolysis experiments at high current density (1 A cm -2 ) for several hours using PVDF as the catalyst binder., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Antioxidant nanozymes are powerful tools to combat oxidative stress, which can be further improved by applying nanozyme mixtures of multiple enzymatic function. Here, cocktails of Prussian blue (PB) nanocubes and copper(II) exchanged ZSM-5 zeolites (CuZ) with enhanced reactive oxygen species (ROS) scavenging activity were developed. Surface functionalization of the particles was performed using polymers to obtain stable colloids, i.e., resistant to aggregation, under a wide range of experimental conditions. The nanozyme cocktails possessed advanced antioxidant properties with multiple enzyme-like functions, catalyzing the decomposition of ROS in cascade reactions. The activity of the mixture far exceeded that of the individual particles, particularly in the peroxidase assay, where an improvement of more than an order of magnitude was observed, pointing to coamplification of the enzymatic activity. In addition, it was revealed that the copper(II) site in the CuZ plays an important role in the decomposition of both superoxide radicals and hydrogen peroxide, as it directly catalyzes the former reaction and acts as cocatalyst in the latter process by boosting the peroxidase activity of the PB nanozyme. The results give important insights into the design of synergistic particle mixtures for the broad-spectrum scavenging of ROS to develop efficient tools for antioxidant treatments in both medical therapies and industrial manufacturing processes.

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 experimental procedures adopted in the literature to obtain kinetic estimates of charge transfer processes and limitations imposed by the spectroscopy technique employed. Time-resolved techniques (e.g., transient absorption-reflection and time-resolved photoluminescence spectroscopy) are commonly employed to probe charge transfer at perovskite/transport layer interfaces. The variation in sample preparation and measurement conditions can produce a wide dispersion of the measured kinetic parameters. The selected time window and the kinetic fitting model employed introduce additional uncertainty. We discuss here evaluation strategies that rely on multiexponential fitting protocols (regular or stretched) and show how the dispersion in the reported values for carrier transfer rate constants can be resolved., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

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 FA 0.83 Cs 0.17 Pb(I 0.83 Br 0.17 ) 3 and TiO 2 single crystals with different orientations of (100), (110), and (111) were probed from subpicosecond to several hundred nanoseconds. It was revealed that the band alignment between the constituents influenced the relative electron extraction process. TiO 2 (100) showed the fastest overall and hot electron transfer, owing to the largest conduction band and Fermi level offset compared to FA 0.83 Cs 0.17 Pb(I 0.83 Br 0.17 ) 3 . It was found that an early electron accumulation in these systems can have an influence on the following electron extraction on the several nanosecond time scale. Furthermore, the existence of a potential barrier at the TiO 2 /perovskite interface was also revealed by performing excitation fluence-dependent measurements.

As cancer cells exhibit an increased uptake of iron, targeting the interaction with iron has become a straightforward strategy in the fight against cancer. This work comprehensively characterizes the chemical properties of 6-methyl-3-{(2 E )-2-[1-(2-pyridinyl)ethylidene]hydrazino}-5 H -[1,2,4]triazino[5,6- b ]indole (VLX600), a clinically investigated iron chelator, in solution. Its protonation processes, lipophilicity, and membrane permeability as well as its complexation with essential metal ions were investigated using UV-visible, electron paramagnetic resonance, and NMR spectroscopic and computational methods. Formation constants revealed the following order of metal binding affinity at pH 7.4: Cu(II) > Fe(II) > Zn(II). The structures of VLX600 (denoted as HL) and the coordination modes in its metal complexes [Cu(II)(LH)Cl 2 ], [Cu(II)(L)(CH 3 OH)Cl], [Zn(II)(LH)Cl 2 ], and [Fe(II)(LH) 2 ](NO 3 ) 2 were elucidated by single-crystal X-ray diffraction. Redox properties of the iron complexes characterized by cyclic voltammetry showed strong preference of VLX600 toward Fe(II) over Fe(III). In vitro cytotoxicity of VLX600 was determined in six different human cancer cell lines, with IC 50 values ranging from 0.039 to 0.51 μM. Premixing VLX600 with Fe(III), Zn(II), and Cu(II) salts in stoichiometric ratios had a rather little effect overall, thus neither potentiating nor abolishing cytotoxicity. Together, although clinically investigated as an iron chelator, this is the first comprehensive solution study of VLX600 and its interaction with physiologically essential metal ions.

Biocompatible Cu(II)-doped layered double hydroxide (CMA) nanoparticles were developed to combat reactive oxygen species. The 2-dimensional nanozymes showed both superoxide dismutase- and catalase-like activities in chemical assays, while proving as efficient antioxidants in the reduction of intracellular oxidative stress. The results indicate the great promise of CMA in antioxidant therapies.

Photoelectrodes with FTO/Au/Sb 2 Se 3 /TiO 2 /Au architecture were studied in photoelectrochemical CO 2 reduction reaction (PEC CO 2 RR). The preparation is based on a simple spin coating technique, where nanorod-like structures were obtained for Sb 2 Se 3 , as confirmed by SEM images. A thin conformal layer of TiO 2 was coated on the Sb 2 Se 3 nanorods via ALD, which acted as both an electron transfer layer and a protective coating. Au nanoparticles were deposited as co-catalysts via photo-assisted electrodeposition at different applied potentials to control their growth and morphology. The use of such architectures has not been explored in CO 2 RR yet. The photoelectrochemical performance for CO 2 RR was investigated with different Au catalyst loadings. A photocurrent density of ∼7.5 mA cm -2 at -0.57 V vs. RHE for syngas generation was achieved, with an average Faradaic efficiency of 25 ± 6% for CO and 63 ± 12% for H 2 . The presented results point toward the use of Sb 2 Se 3 -based photoelectrodes in solar CO 2 conversion applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

In the current work, we first present a simple synthesis method for the preparation of novel Vitamin-B 1 -stabilized few-atomic gold nanoclusters with few atomic layers. The formed nanostructure contains ca. eight Au atoms and shows intensive blue emissions at 450 nm. The absolute quantum yield is 3%. The average lifetime is in the nanosecond range and three main components are separated and assigned to the metal-metal and ligand-metal charge transfers. Based on the structural characterization, the formed clusters contain Au in zero oxidation state, and Vitamin B 1 stabilizes the metal cores via the coordination of pyrimidine-N. The antioxidant property of the Au nanoclusters is more prominent than that of the pure Vitamin B 1 , which is confirmed by two different colorimetric assays. For the investigation into their potential bioactivity, interactions with bovine serum albumin were carried out and quantified. The determined stoichiometry indicates a self-catalyzed binding, which is almost the same value based on the fluorometric and calorimetric measurements. The calculated thermodynamic parameters verify the spontaneous bond of the clusters along the protein chain by hydrogen bonds and electrostatic interactions.

While CO can already be produced at industrially relevant current densities via CO 2 electrolysis, the selective formation of C 2+ products seems challenging. CO electrolysis, in principle, can overcome this barrier, hence forming valuable chemicals from CO 2 in two steps. Here we demonstrate that a mass-produced, commercially available polymeric pore sealer can be used as a catalyst binder, ensuring high rate and selective CO reduction. We achieved above 70% faradaic efficiency for C 2+ products formation at j = 500 mA cm -2 current density. As no specific interaction between the polymer and the CO reactant was found, we attribute the stable and selective operation of the electrolyzer cell to the controlled wetting of the catalyst layer due to the homogeneous polymer coating on the catalyst particles' surface. These results indicate that sophistically designed surface modifiers are not necessarily required for CO electrolysis, but a simpler alternative can in some cases lead to the same reaction rate, selectivity and energy efficiency; hence the capital costs can be significantly decreased., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We measured the exciton dynamics in van der Waals heterojunctions of transition metal dichalcogenides (TMDCs) and organic semiconductors (OSs). TMDCs and OSs are semiconducting materials with rich and highly diverse optical and electronic properties. Their heterostructures, exhibiting van der Waals bonding at their interfaces, can be utilized in the field of optoelectronics and photovoltaics. Two types of heterojunctions, MoS 2 -pentacene and WSe 2 -pentacene, were prepared by layer transfer of 20 nm pentacene thin films as well as MoS 2 and WSe 2 monolayer crystals onto Au surfaces. The samples were studied by means of transient absorption spectroscopy in the reflectance mode. We found that A-exciton decay by hole transfer from MoS 2 to pentacene occurs with a characteristic time of 21 ± 3 ps. This is slow compared to previously reported hole transfer times of 6.7 ps in MoS 2 -pentacene junctions formed by vapor deposition of pentacene molecules onto MoS 2 on SiO 2 . The B-exciton decay in WSe 2 shows faster hole transfer rates for WSe 2 -pentacene heterojunctions, with a characteristic time of 7 ± 1 ps. The A-exciton in WSe 2 also decays faster due to the presence of a pentacene overlayer; however, fitting the decay traces did not allow for the unambiguous assignment of the associated decay time. Our work provides important insights into excitonic dynamics in the growing field of TMDC-OS heterojunctions.

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). By systematically changing the precursors, we have varied the amount and chemical nature of N-functions on the catalyst surface. The CO 2 reduction (CO 2 R) properties of these catalysts were tested in both electrochemical (EC) and thermal catalytic (TC) experiments (i.e., CO 2 + H 2 reaction). CO was the major CO 2 R product in all cases, while CH 4 appeared as a minor product. Importantly, the CO 2 R activity changed with the chemical composition, and the activity trend was similar in the EC and TC scenarios. The activity was correlated with the amount of different N-functions, and a correlation was found for the -NO x species. Interestingly, the amount of this species decreased radically during EC CO 2 R, which was coupled with the performance decrease. The observations were rationalized by the adsorption/desorption properties of the samples, while theoretical insights indicated a similarity between the EC and TC paths., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Antioxidant colloids were developed via controlled heteroaggregation of cerium oxide nanoparticles (CeO 2 NPs) and sulfate-functionalized polystyrene latex (SL) beads. Positively charged CeO 2 NPs were directly immobilized onto SL particles of opposite surface charge via electrostatic attraction (SL/Ce composite), while negatively charged CeO 2 NPs were initially functionalized with poly(diallyldimethylammonium chloride) (PDADMAC) polyelectrolyte and then, aggregated with the SL particles (SPCe composite). The PDADMAC served to induce a charge reversal on CeO 2 NPs, while the SL support prevented nanoparticle aggregation under conditions, where the dispersions of bare CeO 2 NPs were unstable. Both SL/Ce and SPCe showed enhanced radical scavenging activity compared to bare CeO 2 NPs and were found to mimic peroxidase enzymes. The results demonstrate that SL beads are suitable supports to formulate CeO 2 particles and to achieve remarkable dispersion storage stability. The PDADMAC functionalization and immobilization of CeO 2 NPs neither compromised the peroxidase-like activity nor the radical scavenging potential. The obtained SL/Ce and SPCe artificial enzymes are foreseen to be excellent antioxidant agents in various applications in the biomedical, food, and cosmetic industries., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

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 electron scavenger (TCNQ) has dual roles: while it leads to rapid electron transfer from the electrode to TCNQ, enhancing the PEC performance, it also accelerates the decomposition of the CsPbBr 3 photoelectrode. The instability of the films is caused by the TCNQ-mediated halide exchange between the dichloromethane solvent and the LHP film, during PEC operation. Charge transfer and halide exchange pathways were proposed on the basis of in situ spectroelectrochemical and ex situ surface characterization methods, also providing guidance on planning PEC experiments with such systems., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

A major goal within the CO 2 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 CO 2 electrolysis. Here we compare the operation of electrolyzer cells with Ir and Ni anodes and demonstrate that, while Ir is stable under process conditions, the degradation of Ni leads to a rapid cell failure. This is caused by two parallel mechanisms: (i) a pH decrease of the anolyte to a near neutral value and (ii) the local chemical environment developing at the anode (i.e., high carbonate concentration). The latter is detrimental for zero-gap electrolyzer cells only, but the first mechanism is universal, occurring in any kind of CO 2 electrolyzer after prolonged operation with recirculated anolyte., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Titanium dioxide (TiO 2 ) 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 TiO 2 (b-TiO 2 ), allowing better absorption of visible light, which placed this material in the forefront of research. At the same time, hydrogen treatment also introduces trap states, and the question of whether these states are beneficial or harmful is rather controversial and depends strongly on the application. We employed combined surface science and in situ electrochemical methods to scrutinize the effect of these states on the photoelectrochemical (PEC), electrocatalytic (EC), and charge storage properties of b-TiO 2 . Lower photocurrents were recorded with the increasing number of defect sites, but the EC and charge storage properties improved. We also found that the PEC properties can be enhanced by trap state passivation through Li + ion intercalation in a two-step process. This passivation can only be achieved by utilizing small size cations in the electrolyte (Li + ) but not with bulky ones (Bu 4 N + ). The presented insights will help to resolve some of the controversies in the literature and also provide rational trap state engineering strategies., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

An efficient self-supported Cu(II)Bi(III) bimetallic catalyst with a layered structure was designed and developed. By careful characterization of the as-prepared material, the host structure was identified to exhibit a Sillen-type bismutite framework, with copper(II) ions being loaded as guests. The heterogeneous catalyst enabled C-N and C-S arylations under mild reaction conditions and with high chemoselectivities, thus furnishing valuable phenothiazines via heterocyclization with wide substrate tolerance. As corroborated by detailed catalytic studies, the cooperative, bifunctional catalyst, bearing Lewis acid sites along with copper(II) catalytic sites, facilitated an intriguing concerted C-N/C-S heterocyclization mechanism. The heterogeneous nature of the catalytic reactions was verified experimentally. Importantly, the catalyst was successfully recycled and reused multiple times, persevering its original structural order as well as its initial activity.

The preparation of an antioxidant hybrid material by controlled heteroaggregation of manganese oxide nanoparticles (MnO2 NPs) and sulfate-functionalized polystyrene latex (SL) beads was accomplished. Negatively charged MnO2 NPs were prepared by precipitation and initially functionalized with poly(diallyldimethylammonium chloride) (PDADMAC) polyelectrolyte to induce charge reversal allowing decoration of oppositely charged SL surfaces via simple mixing. The PDADMAC-functionalized MnO2 NPs (PMn) aggregated with the SL particles leading to the formation of negatively charged, neutral and positively charged (SPMn) composites. The charge neutralization resulted in rapidly aggregating dispersions, while stable samples were observed once the composites possessed sufficiently high negative and positive charge, below and above the charge neutralization point, respectively. The antioxidant assays revealed that SL served as a suitable substrate and that the PDADMAC functionalization and immobilization of MnO2 NPs did not compromise their catalase (CAT) and superoxide dismutase (SOD)-like activities, which were also maintained within a wide temperature range. The obtained SPMn composite is expected to be an excellent candidate as an antioxidant material for the efficient scavenging of reactive oxygen species at both laboratory and larger scales, even under harsh conditions, where natural antioxidants do not function.

The construction of a donor-acceptor Stenhouse adduct molecular layer on a gold surface is presented. To avoid the incompatibility of the thiol surface-binding group with the donor-acceptor polyene structure of the switch, an interfacial reaction approach was followed. Poly(dopamine)-supported gold nanoparticles on quartz slides were chosen as substrates, which was expected to facilitate both the interfacial reaction and the switching process by providing favorable steric conditions due to the curved particle surface. The reaction between the surface-bound donor half and the CF 3 -isoxazolone-based acceptor half was proved to be successful by X-ray photoelectron spectroscopy (XPS). However, UV-vis measurements suggested that a closed, cyclopentenone-containing structure of the switch formed on the surface irreversibly. Analysis of the wetting behavior of the surface revealed spontaneous water spreading that could be associated with conformational changes of the closed isomer.

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 applications. Understanding the elementary steps of photocorrosion of these materials can aid the endeavor of realizing stable devices. In this Perspective, we discuss both thermodynamic and kinetic aspects of photocorrosion processes occurring at the interface of perovskite photocatalysts and photoelectrodes with different electrolytes. We show how combined in situ and operando electrochemical techniques can reveal the underlying mechanisms. Finally, we also discuss emerging strategies to mitigate photocorrosion (such as surface protection, materials and electrolyte engineering, etc.).

The electrochemical conversion of carbon dioxide (CO 2 ) 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 interfaces, generating carbon monoxide (CO), formic acid (HCOOH), and methane (CH 4 ) as CO 2 reduction products. The formation of CH 4 is significant because it has only been observed on very few Cu-free electrodes. The maximum CH 4 formation rate of 0.33 mA cm -2 was achieved when the most Au/Pb interfaces were present. In situ Raman spectroelectrochemical studies confirmed the stability of the Pb native substoichiometric oxide under the reduction conditions on the Au-Pb catalyst, which seems to be a major contributor to CH 4 formation. Density functional theory simulations showed that without Au, the reaction would get stuck on the COOH intermediate, and without O, the reaction would not evolve further than the CHOH intermediate. In addition, they confirmed that the Au/Pb bimetallic interface (together with the subsurface oxygen in the model) possesses a moderate binding strength for the key intermediates, which is indeed necessary for the CH 4 pathway. Overall, this study demonstrates how bimetallic nanoparticles can be employed to overcome scaling relations in the CO 2 reduction reaction., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

According to the currently accepted structure-property relationships, aceno-pentalenes with an angular shape (fused to the 1,2-bond of the acene) exhibit higher antiaromaticity than those with a 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, different, 8π antiaromatic subunits, a benzocyclobutadiene (BCB) and a pentalene, are combined into, respectively, an angular and a linear topology via an unsaturated six-membered ring. The antiaromatic character of the molecules is supported experimentally by 1 H NMR, UV-vis, and cyclic voltammetry measurements and X-ray crystallography. The experimental results are further confirmed by theoretical studies including the calculation of several aromaticity indices (NICS, ACID, HOMA, FLU, MCI). In the case of the angular molecule, double bond-localization within the connecting six-membered ring resulted in reduced antiaromaticity of both the BCB and pentalene subunits, while the linear structure provided a competitive situation for the two unequal [4 n ]π subunits. We found that in the latter case the BCB unit alleviated its unfavorable antiaromaticity more efficiently, leaving the pentalene with strong antiaromaticity. Thus, a reversed structure-antiaromaticity relationship when compared to aceno-pentalenes was achieved.

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 (CH 3 NH 3 PbBr 1.5 I 1.5 ) films. Upon trapping holes at the iodide site, the iodide gradually gets expelled from the mixed halide film (as iodine and/or triiodide ion), leaving behind re-formed CH 3 NH 3 PbBr 3 domains. The weakening of the Pb-I bond following the hole trapping (oxidation of the iodide site) and its expulsion from the lattice in the form of iodine provided further insight into the photoinduced segregation of halide ions in mixed halide perovskite films. Transient absorption spectroscopy revealed that the iodide expulsion process leaves a defect-rich perovskite lattice behind as charge carrier recombination in the re-formed lattice is greatly accelerated. The selective mobility of iodide species provides insight into the photoinduced phase segregation and its implication in the stable operation of perovskite solar cells.

Owing to its high hole conductivity and ease of preparation, CuI was among the first 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 to show the effect of applied bias on the excited-state dynamics in CuI. Under operating conditions, the recombination of excitons is dependent on the applied bias, and it can be accelerated by decreasing the potential from +0.6 to -0.1 V vs Ag/AgCl. Prebiasing experiments show the persistent and reversible "memory" effect of electrochemical bias on charge carrier lifetimes. The excitation of CuI in a CuI/CsPbBr 3 film provides synergy between both CuI and CsPbBr 3 in dictating the charge separation and recombination., Competing Interests: The authors declare no competing financial interest.

Detailed mechanistic understanding of the optoelectronic features is a key factor in designing efficient and stable photoelectrodes. In situ spectroelectrochemical methods were employed to scrutinize the effect of trap states on the optical and electronic properties of CuI photoelectrodes and to assess their stability against (photo)electrochemical corrosion. The excitonic band in the absorption spectrum and the Raman spectral features were directly influenced by the applied bias potential. These spectral changes exhibit a good correlation with the alterations observed in the charge-transfer resistance. Interestingly, the population and depopulation of the trap states, which are responsible for the changes in both the optical and electronic properties, occur in a different potential/energy regime. Although cathodic photocorrosion of CuI is thermodynamically favored, this process is kinetically hindered, thus providing good stability in photoelectrochemical operation.

Competing Interests: The authors declare no competing financial interest.

The unique optoelectronic properties of lead halide perovskites have triggered a new wave of excitement in materials chemistry during the past five years. Electrochemistry, spectroelectrochemistry, and photoelectrochemistry could be viable tools both for analyzing the optoelectronic features of these materials and for assembling them into hybrid architectures (e.g., solar cells). At the same time, the instability of these materials limits the pool of solvents and electrolytes that can be employed in such experiments. The focus of our study is to establish a stability window for electrochemical tests for all-inorganic CsPbBr 3 and hybrid organic-inorganic MAPbI 3 perovskites. In addition, we aimed to understand the reduction and oxidation events that occur and to assess the damage done during these processes at extreme electrochemical conditions. In this vein, we demonstrated the chemical, structural, and morphological changes of the films in both reductive and oxidative environments. Taking all these results together as a whole, we propose a set of boundary conditions and protocols for how electrochemical experiments with lead halide perovskites should be carried out and interpreted. The presented results will contribute to the understanding of the electrochemical response of these materials and lead to a standardization of results in the literature so that comparisons can more easily be made., Competing Interests: The authors declare no competing financial interest.

The charging of a mesoscopic TiO 2 layer in a metal halide perovskite solar cell can influence the overall power conversion efficiency. By employing CsPbBr 3 films deposited on a mesoscopic TiO 2 film, we have succeeded in probing the influence of electrochemical bias on the charge carrier recombination process. The transient absorption spectroscopy experiments conducted at different applied potentials indicate a decrease in the charge carrier lifetimes of CsPbBr 3 as we increase the potential from -0.6 to +0.6 V vs Ag/AgCl. The charge carrier lifetime increased upon reversing the applied bias, thus indicating the reversibility of the photoresponse to charging effects. The ultrafast spectroelectrochemical experiments described here offer a convenient approach to probe the charging effects in perovskite solar cells.

Photoelectrochemical hydrogen evolution is a promising avenue to store the energy of sunlight in the form of chemical bonds. The recent rapid development of new synthetic approaches enables the nanoscale engineering of semiconductor photoelectrodes, thus tailoring their physicochemical properties toward efficient H 2 formation. In this work, we carried out the parallel optimization of the morphological features of the semiconductor light absorber (NiO) and the cocatalyst (Pt). While nanoporous NiO films were obtained by electrochemical anodization, the monodisperse Pt nanoparticles were synthesized using wet chemical methods. The Pt/NiO nanocomposites were characterized by XRD, XPS, SEM, ED, TEM, cyclic voltammetry, photovoltammetry, EIS, etc. The relative enhancement of the photocurrent was demonstrated as a function of the nanoparticle size and loading. For mass-specific surface activity the smallest nanoparticles (2.0 and 4.8 nm) showed the best performance. After deconvoluting the trivial geometrical effects (stemming from the variation of Pt particle size and thus the electroactive surface area), however, the intermediate particle sizes (4.8 and 7.2 nm) were found to be optimal. Under optimized conditions, a 20-fold increase in the photocurrent (and thus the H 2 evolution rates) was observed for the nanostructured Pt/NiO composite, compared to the benchmark nanoparticulate NiO film.

In the search for stable and efficient photocatalysts beyond TiO2 , the tungsten-based oxide semiconductors silver tungstate (Ag2 WO4 ), copper tungstate (CuWO4 ), and zinc tungstate (ZnWO4 ) were prepared using solution combustion synthesis (SCS). The tungsten precursor's influence on the product was of particular relevance to this study, and the most significant effects are highlighted. Each sample's photocatalytic activity towards methyl orange degradation was studied and benchmarked against their respective commercial oxide sample obtained by solid-state ceramic synthesis. Based on the results herein, we conclude that SCS is a time- and energy-efficient method to synthesize crystalline binary tungstate nanomaterials even without additional excessive heat treatment. As many of these photocatalysts possess excellent photocatalytic activity, the discussed synthetic strategy may open sustainable materials chemistry avenues to solar energy conversion and environmental remediation., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)