Rhenium electroless deposition on p-Si(1 0 0) from HF solutions under illumination: Hydrogen evolution reaction onto p-Si/Re systems

In this study we examined the rhenium photoelectroless deposition process onto p-Si(1 0 0) from HF solutions. In the first stage an energetic characterization through capacitance measurements (Mott-Schottky plots) of the p-Si/HF interface was done. Before the rhenium photoelectroless deposition process, a voltammetric and photovoltammetric analysis of p-Si in ReO₄^- / HF solutions was done. In this study, a decrease of the rhenium deposition charge was observed as a function of the increased HF concentration. This behavior was attributed to competition with the silicon dissolution process when an increased HF concentration was present in the electrolytic bath. A morphologic analysis was completed by means of atomic force microscopy (AFM) for the rhenium deposits obtained by photoelectroless process at different HF concentrations and different deposition times. X-ray photoelectron spectroscopy (XPS) technique was utilized to characterize the rhenium deposits, and it was concluded that the films formed by the photoelectroless process were metallic rhenium with only the uppermost atomic layer containing rhenium oxide species. The hydrogen evolution reaction (HER) on the different p-Si/Re electrode systems synthesized was studied. For the HER on p-Si(1 0 0)/Re electrode systems an overpotential decrease of 0.2 V and a photocurrent increase between one and two orders of magnitude, compared with p-Si(1 0 0) and metallic Re, was found. Additionally, the kinetic parameters of the cathodic reactions in the p-Si and p-Si/Re acidic media were estimated using intensity modulated photocurrent spectroscopy (IMPS). A brief analysis from this technique was done. According to these results, the p-Si/Re electrode system could be a potential photoelectrocatalyst for the HER.