Split second: The photocatalytic activity of gallium oxide (β-Ga₂O₃) depends strongly on the co-catalysts CuO_x and chromia, which can be efficiently deposited in a stepwise manner by photoreduction of Cu²⁺ and CrO₄^2-. The water-splitting activity can be tuned by varying the Cu loading in the range 0.025–1.5 wt %, whereas the Cr loading is not affecting the rate as long as small amounts (such as 0.05 wt %) are present. Chromia is identified as highly efficient co-catalyst in the presence of CuO_x: it is essential for the oxidation of water

In pursuance of efficient tools for the local analysis and characterization of novel photoelectrocatalytic materials, several SECM-based techniques have been developed, aiming on the combined benefit of a local irradiation of the analyzed sample and a microelectrode probe for the localized electrochemical analysis of the surface. We present the development and application of scanning photoelectrochemical microscopy (SPECM) for the laterally resolved characterization of photoelectrocatalytic materials. Particularly, the system was developed for the photoelectrochemical characterization of n-type semiconductor-based photoanodes for water splitting. By using the tip microelectrode simultaneously for local irradiation and as an electrochemical probe, SPECM was capable to simultaneously provide information about the local photocurrent generated at the sample under irradiation and to detect the photoelectrocatalytically evolved oxygen at the microelectrode. In combination with a novel means of irradiation of the interrogated sample, local analysis of semiconductor materials for light-induced water splitting with improved lateral resolution is achieved.

The influence of elements Mo and W on the PEC response of BiVO4 based thin films is visualized concerning the photocurrent and in situ detection of locally evolved O2 at a photoabsorber.

The search for suitable materials for solar water splitting is addressed with combinatorial material science methods. Thin film Fe-V-O materials libraries were synthesized using combinatorial reactive magnetron cosputtering and subsequent annealing in air. The design of the libraries comprises a combination of large compositional gradients (from FeVO to FeVO ) and thickness gradients (from 140 to 425 nm). These material libraries were investigated by high-throughput characterization techniques in terms of composition, structure, optical, and photoelectrochemical properties to establish correlations between composition, thickness, crystallinity, microstructure, and photocurrent density. Results show the presence of the FeVO phase from ∼11 to 42 at. % Fe (toward low-Fe region) and the FeVO phase from ∼37 to 79 at. % Fe (toward Fe-rich region). However, as a third phase, FeO is present throughout the compositional gradients (from low-Fe to Fe-rich region). Material compositions with increasing crystallinity of the FeVO phase show enhanced photocurrent densities (∼160 to 190 μA/cm) throughout the thickness gradients whereas compositions with the FeVO phase show comparatively low photocurrent densities (∼28 μA/cm). The band gap energies of Fe-V-O films were inferred from Tauc plots. The highest photocurrent density of ∼190 μA/cm was obtained for films with ∼54 to 66 at. % Fe for the FeVO phase with ∼2.04 eV for the indirect and ∼2.80 eV for the direct band gap energies.

In thin film deposition processes, the deposition temperature is one of the crucial process parameters for obtaining films with desired properties. Usually the optimum deposition temperature is found by conducting several depositions sequentially in a time consuming process. This paper demonstrates a facile and rapid route of the simultaneous thin film deposition at six different deposition temperatures ranging from 100 to 1000 8C. Cuprite (Cu 2 O) was chosen for the study as this material is of interest for energy applications. The thin films are assessed for their crystallographic, microstructural, Raman scattering, and photoelectrochemical properties. The results show that the utilization of a step heater leads to the rapid optimization of thin film microstructures of an absorber material used in photoelectrochemistry. This results in a structure zone diagram for Cu 2 O. For a substrate temperature of 600 8C, an optimum between crystallinity and morphology occurs. 1 Introduction Thin film semiconductors in photoelectrochemical applications need to fulfil numerous properties. Whereas the search for new absorber and catalytic materials by combinatorial and high-throughput methods is currently addressed, the high-throughput optimization of deposition parameters, e.g., deposition temperature, however, is less developed. Finding optimal deposition conditions for even relatively simple metal oxide semiconductors for photoelectrochemical applications [1], usually requires careful evaluation of the different properties of a thin film like morphology, crystal structure, and interface formation [2][3][4][5]. In reactive magnetron sputtering, these properties can be tuned by deposition parameters like applied power, gas flow, substrate rotation, deposition geometry, total or partial gas pressure, and substrate temperature. These parameters are, however, interdependent. Attaining the desired metal oxide phase (e.g., competing phase formation between CuO and Cu 2 O) adds to the overall complexity of the problem of finding optimal deposition parameters [6]. Evaluating all possible optimization