TiO₂/ZrO₂ Nanoparticle Composites for Electrochemical Hydrogen Evolution

Composites of different semiconductors are found to show much improved electronic conductivity and decreased charge transfer resistance. In this work, this hypothesis is tested by preparing composite heterostructures of chemically and structurally dissimilar and wide-bandgap semiconductors, titania (TiO2) and zirconia (ZrO2). Herein, the underpotential hydrogen generation ability of the composite nanoparticles is studied for the first time. The dissimilarity in coordination can create charge imbalance once the composite of these two materials is formed, which in turn can increase the surface acidity and the active sites for proton adsorption as proved through various analytical techniques. The composite of separately incompetent hydrogen evolution reaction (HER) catalysts shows improved HER activity due to improved charge transfer between the composite catalyst and reactant caused by the generation of the new electronic states. To improve the electronic conduction, we have performed the reduction of TiO2/ZrO2 binary metal oxide composite, which results in oxygen vacancies in the composite. The reduced counterpart of the composite is found to possess semimetallic properties and shows outstanding high stability and 7 times increase in HER current density at −0.6 V along with a very small overpotential of only ∼160 mV penalty to have a HER current density of 10 mA/cm2.