Preparation of h-WO3/CuWO4 microsphere and single crystalline CuWO4 nanoparticles and their electrocatalytic activity

In this work, h-WO3/CuWO4 (hexagonal WO3/CuWO4) core-shell microsphere and single crystalline CuWO4 nanoparticles were synthesized by two step process using polyol assisted hydrothermal-hybrid microwave annealing (HMA) process. In the sake of comparison, conventional annealing (CA) process showed CuWO4/mWO(3) (CuWO4/monoclinic WO3) and CuWO4/CuO microrods by in-situ annealing of as-prepared particles obtained under pH 3 and 9 respectively. The h-WO3/CuWO4 microsphere showed onset potential of 350 mV, and three fold times small and cathodic overpotential (eta(c)) of 20 mV for current density (j) = 3 mA/cm(2) compared to CuWO4/m-WO3 in hydrogen evolution reaction (1 M H2SO4). For oxygen evolution reaction in 0.1 M KOH electrolyte, single crystalline CuWO4 showed a small onset potential of 350 mV and anodic overpotential (eta(a)) of 1.0 V for the j = 10 mA/cm(2) compared to CA treated CuWO4.