Band-gap engineering of tungsten oxide nanoplates by cobalt ferrite co-catalyst for solar water oxidation

Abstract

Abstract Tungsten oxide exhibits a favourable band gap for photo-electrochemical applications like water splitting and photo oxidation of water pollutants but suffers from its fast recombination of photo generated electrons and holes due to poor electrical conductivity and its hydrogen evolution level being below the conduction band minimum. In this work, we have incorporated cobalt ferrite nanocrystals as co-catalyst in a hydrothermally synthesized tungsten oxide (WO3) photoanode with an aim to arrest the fast recombination process. Characterization of the nanocomposite containing 5 mol% cobalt ferrite by multiple te chniques confirmed formation of monoclinic WO3nanoplate like structures containing stoichiometric CoFe2O4phase whereas optical absorption spectroscopy gave its optical band gap as 2.1 eV. Electrochemical impedance spectroscopy (EIS), Mott-Schottky analysis and linear sweep voltammetry (LSV) were conducted under illuminated (1.5AM G solar simulated light) and dark conditions that revealed a reduction in the onset potential of pristine tungsten oxide photoanode by ~0.25 V as a result of incorporation of 5 mol% cobalt ferrite nanocrystals owing to an efficient electron transfer before recombination. The photocurrent obtained from the composite photoanode was also found to be 10 times higher than that from bare tungsten oxide photoanode suggesting its potential use as anode material for photoelectrochemical water splitting.