Insertion of low-valent metal into interstitial sites of WO3 for enhanced photoelectrochemical activity

Abstract

The presence of low valent metals along with O vacancies in WO3 allows critical tuning of both intrinsic and extrinsic properties transforming WO3 to be capable of performing both oxygen evolution (OER) and hydrogen evolution reactions (HER) under the simulated sunlight. Given this, the proposed work provides a modified synthesis approach to obtain the low valent Hf doped WO3 nanorods on the transparent conducting substrate for the overall water-splitting activity. The experimental data confirms that the doping of Hf leads to the essential modifications in WO3 including the exposure of (002) facet, decrease in band gap, shift in band edge towards negative potential, introduction of oxygen vacancies, and effective charge diffusion/transfer. Owing to the favorable intrinsic and extrinsic modifications, WO3 exhibits enhanced photocurrents, incident photon-to-current efficiency (IPCE), and applied bias photon-to-current efficiencies (ABPE) compared to its pristine counterparts. Based on the results, Hf is found to occupy W lattice positions and the simultaneous presence of Hf and O vacancies in the lattice induces essential changes in WO3 properties. Importantly, the findings in the proposed study demonstrate the use of Hf as a dopant to WO3 for the ideal transformation in intrinsic and extrinsic properties for enhanced overall water splitting.