Microwave facilitated HfO2-ZnO nanospheres: Goaded electro-catalytic and electrical functionality maximization in multifold energy systems

Abstract

This work presents the first report on the microwave facilitated synthesis, characterization, and energy application of the novel hafnium oxide-zinc oxide (HfO2-ZnO) nanospheres. The prepared heterostructure expressed an alleviation in the band gap energy from 3.54 to 3.17 eV and possessed mixed phases i.e. monoclinic and hexagonal wurtzite. The nanospheres underwent reduction in the average crystallite size from 51.33 to 47.81 nm. Hafnia and HfO2-ZnO existed as irregularly distributed spherical nanoparticles with moderate agglomeration. HfO2-ZnO nanospheres exhibited bifunctionality towards generation of oxygen and hydrogen. However, the hydrogen production excelled with the impressively lower ηHER = 128 mV and Tafel slope value of 52.8 mV dec−1. This electro-catalyst is marked by commendable durability shown by its intactness for 1400 min in electrolyte. HfO2-ZnO nanospheres decorated electrode was pseudocapacitive with the faster kinetics and it reached the specific capacitance of 672 F g−1. As interface engineering agents, HfO2-ZnO nanospheres passivated the defects in the perovskite solar cell and improved the transferal of holes to the photo-cathode. This is shown by the improvement in the power conversion efficiency from 9.42 % for hafnia to 16.27 % upon nanocomposite formation. The developed nano-composite is a sustainable and energy efficient choice for varied energy applications.