Enhanced hydrogen evolution by nanostructures CuO composites

Abstract Herein, I report nano size effect on electrocatalytic hydrogen evolution reaction (HER) by using nano-micron (n-µ) composites of CuO. These n-µ CuO composites were synthesized by mixing copper oxalate nanorods and CuO in different (20–80 weight percentage) ratios followed by heating at 350 °C in air. As the amount of copper oxalate increases in the in the mixture of nano-micron composites, there is a decrease in the particle size (50–20 nm) of the composites. The pure nano and micron-sized CuO particles was found to be the size of ~ 15 nm and ~ 110 nm respectively. On the electrochemical HER study the highest (272 mA/cm2mg) and lowest (3.8 mA/cm2mg) current density (hydrogen evolution) was observed for pure nano and micron-sized particles respectively at − 1.3 V potential for Ag/AgCl working electrode (− 0.293 V vs. RHE) on electroactive surface area. In case of n-µ composites, it is found that as the amount of nano sized particles increases there is increase in current density due to increase in surface area and interconnectivity of the nanoparticles. The CuO nanoparticles are very stable over 500 cycles. The present study of nano-micron composites show the combined effect of nanoscale advantages (high activity) with microscale advantages (conductivity and mechanical stability) for different potential applications. Graphical abstract