Mitigation of ohmic losses and mass transport limitations enables a large area BiVO4-based water splitting device with a solar-to-hydrogen efficiency of 2.1%.

Metal chalcogenide thin films have a wide variety of applications and potential uses. Tin­(II) sulfide is one such material which presents a significant challenge with the need for high quality SnS, free of oxide materials (e.g., SnO2) and higher tin sulfides (e.g., Sn2S3 and SnS2). This problem is compounded further when the target material exhibits a number of polymorphic forms with different optoelectronic properties. Unlike conventional chemical vapor deposition (CVD) and atomic layer deposition (ALD), which rely heavily on having precursors that are volatile, stable, and reactive, the use of aerosol assisted CVD (AA-CVD) negates the need for volatile precursors. We report here, for the first time, the novel and structurally characterized single source precursor (1), (dimethylamido)­(N-phenyl-N′,N′-dimethylthiouriate)­tin­(II) dimer, and its application in the deposition, by AA-CVD, of phase-pure films of SnS. A mechanism for the oxidatively controlled formation of SnS from precursor 1 is also reported. Significantly, thermal control of the deposition process allows for the unprecedented selective and exclusive formation of either orthorhombic-SnS (α-SnS) or zinc blende-SnS (ZB-SnS) polymorphs. Thin films of α-SnS or ZB-SnS have been deposited onto Mo, fluorine doped tin oxide (FTO), Si, and glass substrates at the optimized deposition temperatures of 375 and 300 °C, respectively. The densely packed polycrystalline thin films have been characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, Raman spectroscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy analysis. These data confirmed the phase purity of the SnS formed. Optical analysis of the α-SnS and ZB-SnS films shows distinctly different optical properties with direct band gaps of 1.34 and 1.78 eV, respectively. Furthermore, photoelectrochemical and external quantum efficiency (EQE) measurements were undertaken to assess the optoelectronic properties of the deposited samples. We also report for the first time the ambipolar properties of the ZB-SnS phase.

The development of earth‐abundant catalysts for selective electrochemical CO2 conversion is a central challenge. CuSn bimetallic catalysts can yield selective CO2 reduction toward either CO or formate. This study presents oxide‐derived CuSn catalysts tunable for either product and seeks to understand the synergetic effects between Cu and Sn causing these selectivity trends. The materials undergo significant transformations under CO2 reduction conditions, and their dynamic bulk and surface structures are revealed by correlating observations from multiple methods—X‐ray absorption spectroscopy for in situ study, and quasi in situ X‐ray photoelectron spectroscopy for surface sensitivity. For both types of catalysts, Cu transforms to metallic Cu0 under reaction conditions. However, the Sn speciation and content differ significantly between the catalyst types: the CO‐selective catalysts exhibit a surface Sn content of 13 at. % predominantly present as oxidized Sn, while the formate‐selective catalysts display an Sn content of ≈70 at. % consisting of both metallic Sn0 and Sn oxide species. Density functional theory simulations suggest that Snδ+ sites weaken CO adsorption, thereby enhancing CO selectivity, while Sn0 sites hinder H adsorption and promote formate production. This study reveals the complex dependence of catalyst structure, composition, and speciation with electrochemical bias in bimetallic Cu catalysts.

The earth-abundant ternary compound BaZrS3, which crystallizes in the perovskite-type structure, has come into view as a promising candidate for photovoltaic applications. We present the synthesis and characterization of polycrystalline perovskite-type BaZrS3 thin films. BaZrO3 precursor layers were deposited by pulsed laser deposition and sulfurized at various temperatures in an argon-diluted H2S atmosphere. We observe increasing incorporation of sulfur for higher annealing temperatures, accompanied by a red shift of the absorption edge, with a bandgap of E g = 1.99 eV and a large absorption strength >105 cm–1 obtained for sulfurization temperatures of 1000 °C. X-ray diffraction analysis and SEM indicate enhanced crystallization at the higher annealing temperatures, but no evidence for a crystalline solid solution between the BaZrO3 and BaZrS3 phases is found. The charge carrier sum mobility estimated from optical-pump–terahertz-probe spectroscopy indicates increasing mobilities with increasing sulfurization temperature, reaching maximum values of up to ∼2 cm2 V–1 s–1.

Photoelectrochemical water splitting is a promising route to produce hydrogen from solar energy. However, corrosion of photoelectrodes remains a fundamental challenge for their implementation. Here, we reveal different dissolution behaviors of BiVO 4 photoanode in pH-buffered borate, phosphate, and citrate (hole-scavenger) electrolytes, studied in operando employing an illuminated scanning flow cell. We demonstrate that decrease in photocurrents alone does not reflect the degradation of photoelectrodes. Changes in dissolution rates correlate to the evolution of surface chemistry and morphology. The correlative measurements on both sides of the liquid–semiconductor junction provide quantitative comparison and mechanistic insights into the degradation processes.