Enhancing the Photoelectrochemical Water Oxidation Reaction of BiVO₄ Photoanode by Employing Carbon Spheres as Electron Reservoirs

Abstract

The rate-determining step of the photoelectrochemical (PEC) water splitting is the water oxidation reaction at the photoanode, which is 4 orders of magnitude slower than the water reduction reaction at the photocathode. In a conventional process to accelerate the water oxidation, oxygen evolution cocatalysts (OECs) are usually used on the surface of a photoanode. As an alternative strategy, we considered employing a composite photoanode made up of a semiconductor and carbon spheres, for it is expected that the photogenerated electrons on the semiconductor particles can be captured by the carbon spheres as electron reservoirs and leave the photogenerated holes on the surface of the semiconductor particles, which promotes the effective separation of photogenerated electrons and holes. More importantly, the holes accumulated in the valence band accelerate the water oxidation reaction rate with the rapid release of electrons stored on the carbon sphere. Therefore, the composite photoanode achieves a higher photocurrent at a lower applied bias. We provide a proof of concept for this strategy by preparing a composite photoanode by combining bismuth vanadium oxide BiVO4 with carbon spheres and find that the resulting photoanode displays a remarkable enhancement in the rate of the photoanode water oxidation.

Emerging Surface, Bulk, and Interface Engineering Strategies on BiVO4 for Photoelectrochemical Water Splitting

“…Unlike surface engineering which only impacts the surface of BiVO 4 , bulk engineering may modify structure of BiVO 4 either entirely or partially in terms of its chemical Reproduced with permission. [43] Copyright 2020, American Chemical Society. Metal oxide/hydroxide-based cocatalysts.…”

Enhancing the Photoelectrochemical Water Oxidation Activity of α‐Fe2O3 Thin Film Photoanode by Employing rGO as Electron Transfer Mediator and NiFe‐LDH as Cocatalyst

“…These results suggested that the rGO nanosheets and NiFe‐LDH cocatalyst can both independently improve the PEC activity of α‐Fe 2 O 3 photoanode. In α‐Fe 2 O 3 /rGO composite, the rGO nanosheets act as the unique electron transfer mediators and efficiently separate the photoinduced electron‐hole pairs generated in the α‐Fe 2 O 3 absorber [42] . As for NiFe‐LDH cocatalyst in α‐Fe 2 O 3 /NiFe‐LDH photoanode, it acts as the additional active sites which lowers the energy barrier and perfects the surface kinetics in water oxidation reaction.…”

BiVO4 Ceramic Photoanode with Enhanced Photoelectrochemical Stability

“…The 1% Mo doped BiVO 4 photoanode was prepared with the spin-coating method and then calcined at a high temperature [ 26 , 27 ]. FTO glass cleaned by ethanol, acetone, deionized water, and glycol was used as the substrate.…”