Orderly decoupled dynamics modulation in nanoporous BiVO4 photoanodes for solar water splitting

Abstract

Efficient photoelectrochemical (PEC) water splitting holds great promise for sustainable production of green hydrogen by using abundant solar energy. The design of photoanodes operating water oxidation reaction (WOR) remains a significant challenge in overall efficiency optimization of photo-induced charge multistage dynamics including charge generation, separation and transfer. Herein, we propose an orderly decoupled modulation strategy via tradeoff among multistage dynamics to achieve an overall efficiency upgrade for PEC water oxidation. This concept is demonstrated typically on nanoporous BiVO4 photoanode that features with film thickness dilemma toward carrier transport or light absorption to realize a significant increase in the product of three dynamics efficiencies. Specifically, tailoring granular layer thickness to smooth charge transport enables an almost complete charge separation at different spatial directions; then activating surface with molecular borate sites accelerates surface hole transfer into WOR; finally scaled-up optical thickness by lamination compensates for light absorption but with no loss of charge separation. With a win-win outcome of photon acquisition and charge utilization, trinal BiVO4 photoanode exhibits an excellent photocurrent density up to approximately 6.2 mA cm−2 at 1.23 V versus reversible hydrogen electrode under simulated 1 sun irradiation (100 mW cm−2, AM 1.5 G). This work describes a simple and feasible methodology that is universal for different semiconducting electrodes to improve multistage charge dynamics for various PEC applications.