| Summary: | Photoelectrochemical (PEC) water splitting in a pH-neutral electrolyte has attracted more and more attention in the field of sustainable energy. Bismuth vanadate (BiVO<sub>4</sub>) is a highly promising photoanode material for PEC water splitting. Additionally, cobaltous phosphate (CoPi) is a material that can be synthesized from Earth’s rich materials and operates stably in pH-neutral conditions. Herein, we propose a strategy to enhance the charge transport ability and improve PEC performance by electrodepositing the in situ synthesis of a CoPi layer on the BiVO<sub>4</sub>. With the CoPi co-catalyst, the water oxidation reaction can be accelerated and charge recombination centers are effectively passivated on BiVO<sub>4</sub>. The BiVO<sub>4</sub>/CoPi photoanode shows a significantly enhanced photocurrent density (<i>J</i><sub>ph</sub>) and applied bias photon-to-current efficiency (ABPE), which are 1.8 and 3.2 times higher than those of a single BiVO<sub>4</sub> layer, respectively. Finally, the FTO/BiVO<sub>4</sub>/CoPi photoanode displays a photocurrent density of 1.39 mA cm<sup>−2</sup> at 1.23 V<sub>RHE</sub>, an onset potential (<i>V</i><sub>on</sub>) of 0.30 V<sub>RHE</sub>, and an ABPE of 0.45%, paving a potential path for future hydrogen evolution by solar-driven water splitting.
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