Tailoring electrochemical efficiency of hydrogen evolution by fine tuning of TiO_x/RuO_x composite cathode architecture

Here we report an approach to design composite cathode based on TiO_x nanotubes decorated with RuO_x nanowhiskers for efficient hydrogen evolution. We tailor catalytic activity of the cathodes by adjustment of morphology of TiO_x nanotubular support layer along with variation of RuO_x loaded mass and assess its performance using electrochemical methods and wavelet analysis. The highest energy efficiency of hydrogen evolution is observed in 1 M H₂SO₄ electrolyte to be ca. 64% at −10 mA/cm² for cathodes of the most developed area, i.e. smaller diameter of tubes, with enhanced RuO_x loading. The efficiency is favored by detachment of small hydrogen bubbles what is revealed by wavelet analysis and is expressed in pure noise at wavelet spectrum. At increased current density, −50 or −100 mA/cm², better efficiency of composite cathodes is supported by titania nanotubes of larger diameter due to an easier release of large hydrogen bubbles manifested in less periodic events appeared in the frequency region of 5–12 s at the spectra. We have shown that efficiency of the catalysts is determined by a pre-dominant type of hydrogen bubble release at different operation regimes depending on specific surface and a loaded mass of ruthenia.