Optical, Electrochemical, and Photoelectrochemical Behavior of Copper Pyrovanadate: A Unified Theoretical and Experimental Study
Abbas Vali, Hori Pada Sarker, Beatriz Heredia Cervera, Ingrid Rodríguez‐Gutiérrez, Mohammad Kabir Hossain, Muhammad N. Huda, Gerko Oskam, Krishnan Rajeshwar
Abstract
Copper vanadates have been important to the development of new-generation photoelectrodes for solar water splitting and hydrogen generation. Of these, copper pyrovanadate (β-Cu2V2O7), the 2:1 ternary compound derived from CuO and V2O5, has been of particular interest to the solar fuel community. This n-type semiconductor has shown the highest photocurrent for water oxidation at 1.23 V versus reversible hydrogen electrode and exhibits good photostability in aqueous media of pH 9.2. However, further successful application of this material in photoelectrochemical (PEC) devices hinges on a comprehensive understanding of its optical, electrochemical, and optoelectronic attributes. This was done in this study by a combination of density-functional theory (for the structural, magnetic, and optical characterization) and experiments, with the latter using both small-signal (intensity-modulated photocurrent spectroscopy, IMPS) and large-signal, transient photocurrent (TP) analyses. Both IMPS and TP measurements yielded complementary and self-consistent insights into the rate constants for hole transfer and carrier recombination at the irradiated β-Cu2V2O7/electrolyte interface, specifically their dependence on the applied bias potential. The information from PEC data analyses was also self-consistent with that garnered from the optical (diffuse reflectance spectroscopy) data.