Energetics and dynamics of the interface of RuS2 and implications for photoelectrolysis of water

Photocorrosion at Irradiated Perovskite/Electrolyte Interfaces

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.).

Design Considerations of Efficient Photo-Electrosynthetic Cells and its Realization Using Buried Junction Si Thin Film Multi Absorber Cells

As is obvious from previous work on semiconductor photoelectrochemistry, single junction semiconductors do not provide either the required maximum photovoltage or a high photocurrent for solar water splitting, which is required for efficient stand-alone devices. From these experiences we conclude, that multi-junction devices must be developed for bias-free water splitting. In this article we present our design considerations needed for the development of efficient photo-electro-synthetic cells, which have guided us during the DFG priority program 1613. At first, we discuss the fundamental requirements, which must be fulfilled to lead to effective solar water splitting devices. Buried junction and photoelectrochemical arrangements are compared. It will become clear, that the photovoltaic (PV) and electrochemical (EC) components can be optimized separately, but that maximized conversion efficiencies need photovoltages produced in the photovoltaic part of the device, which are adapted to the electrochemical performance of the electrolyzer components without energetic losses in their coupling across the involved interfaces. Therefore, in part 2 we will present the needs to develop appropriate interface engineering layers for proper chemical and electronic surface passivation. In addition, highly efficient electrocatalysts, either for the hydrogen or oxygen evolution reaction (HER, OER), must be adjusted in their energetic coupling to the semiconductor band edges and to the redox potentials in the electrolyte with minimized losses in the chemical potentials. The third part of our paper describes at first the demands and achievements on developing multijunction thin-film silicon solar cells. With different arrangements of silicon stacks a wide range of photovoltages and photocurrents can be provided. These solar cells are applied as photocathodes in integrated directly coupled PV-EC devices. For this purpose thin Pt and Ni catalyst layers are used on top of the solar cells for the HER and a wire connected RuO2 counter electrode is used for the OER. Electrochemical stability has been successfully tested for up to 10,000 s in 0.1 M KOH. Furthermore, we will illustrate our experimental results on interface engineering strategies using TiO2 as buffer layer and Pt nanostructures as HER catalyst. Based on the obtained results the observed improvements, but also the still given limitations, can be related to clearly identified non-idealities in surface engineering either related to recombination losses at the semiconductor surface reducing photocurrents or due to not properly-aligned energy states leading to potential losses across the interfaces.

Onset potential behavior in α-Fe2O3photoanodes: the influence of surface and diffusion Sn doping on the surface states

Donor density and surface states of Fe₂O₃viaSn doping control the water oxidation and onset potential.

Ruthenium sulphide thin layers as catalysts for the electrooxidation of water

Crystalline RuS(2) layers were prepared on titanium sheets by reactive magnetron sputtering using a metallic ruthenium target and a H(2)S-Ar mixture as process gas. The ability of these layers for the electrooxidation of water (OER) was investigated by differential electrochemical mass spectrometry (DEMS) in 0.5 M H(2)SO(4) electrolyte. It was observed that the activity for water oxidation is increased with increasing temperature of the titanium substrate during the sputter deposition process whereas a competitive corrosion process is diminished. The reason for this effect seems to be a better crystallinity of these layers at higher substrate temperatures as it is proved by XRD analysis. In contrast to RuS(2) single crystals no photo effect could be observed on the sputtered layers under illumination with a tungsten lamp. Time resolved microwave conductivity analysis indicates the presence of mobile charge carriers after illumination but apparently these cannot participate in the electrooxidation of water.