Comprehensive multi-parameter study for a reliable photodeposition of co-catalyst nanoparticles on titanium dioxide.

RuO 2 /TiO 2 catalysts have shown broad use in promoting a variety of photocatalytic phenomena, such as water splitting and the photodecomposition of organic dyes and pollutants. Most current methods of photodepositing ruthenium oxide species (RuO x ) onto titanium dioxide (TiO 2 ) films involve precursors that are either difficult to produce and prone to decomposition, such as RuO 4 , or require high-temperature oxidations, which can reduce the quality of the resulting catalyst and increase the risks and toxicity of the procedure. The present work demonstrates the photodeposition of RuO x onto TiO 2 films, using potassium perruthenate (KRuO 4 ) as a precursor, by improving substantially a procedure known to work on TiO 2 nanopowders. In addition to demonstrating the applicability of this method of photodeposition to TiO 2 films, this work also explores the importance of the material phase of the TiO 2 substrate, outlines viable concentrations and photodeposition times at a given optical intensity, and demonstrates that the morphology of the photodeposited nanostructures changes from cauliflower-like spheroids to a matted, porous sponge-like structure with the addition of methanol to the precursor solution. This morphology change has not been documented previously. By providing an explanation for this difference in the morphology, this work provides both newer insights into the photodeposition process and provides an excellent foundation for future procedures, allowing a more targeted and controlled deposition based on the desired morphology.

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A computational model of a photoelectrochemical cell describing the influence of competing surface reactions to the operation of the cell is presented. The model combines an optical simulation for the incident light intensity with fully self-consistent solution of drift-diffusion equations to accurately calculate the electronic state of the semiconductor electrode in a photoelectrochemical cell under operation. The solution is calculated for the full thickness of a typical wafer, while simultaneously solving the thin surface charge region with sufficient precision. In addition to comparing the simulated current–voltage response with experimental data, the simulation is shown to replicate experimental results from electrochemical impedance spectroscopy (EIS) measurements. The results show that considering optical losses in the system is crucial for accurate simulation. The model is capable of selectively characterizing the impact of material parameters on both current–voltage response and interface capacitance, while revealing the internal dynamics of the quasi-Fermi levels that are inaccessible by experimental methods.