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

The presence of low valent metals along with O vacancies in WO 3 allows critical tuning of both intrinsic and extrinsic properties transforming WO 3 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 WO 3 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 WO 3 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, WO 3 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 WO 3 properties. Importantly, the findings in the proposed study demonstrate the use of Hf as a dopant to WO 3 for the ideal transformation in intrinsic and extrinsic properties for enhanced overall water splitting. • A modified synthesis approach is proposed for Hf-WO 3 thin film fabrication. • Hf doping changes the exposed facet to the (200) plane to favor OER activity. • Enhanced photocurrent of 1.18 mA cm -2 was recorded for Hf-WO 3 . • Both bulk and surface properties are modified via Hf doping in WO 3 .