A BiVO4-Based Photoanode with Stacked Functional Layers for Improved Photoelectrochemical Chlorine Evolution under Low External Bias

Abstract

Photoelectrochemical (PEC) chlorine production represents a promising alternative to the energy-intensive chlor-alkali processes for chlorine-based disinfectant industry. Although cocatalyst-loaded BiVO4 photoanodes exhibited considerable chlorine yields at high external bias, the energy conversion efficiency remained unsatisfactory at low bias due to insufficient charge transport directionality, which results from the lack of a strong long-range electric field or selective charge filtering mechanism. Herein, we designed a stacked-layered photoanode integrating a photoelectric conversion layer (PCL), a hole transport layer (HTL), and a chlorine evolution layer (CEL). HTL extracts holes from PCL and directs them to CEL, suppressing recombination and enhancing the energy conversion efficiency. Consequently, under a low bias of 0.8 V vs RHE in simulated seawater, the stacked-layered photoanode achieved half a magnitude enhancement in photocurrent and a 16-fold increase in chlorine yield compared with BiVO4. Our study provides a versatile strategy for optimizing directional charge migration in PEC reactions by integrating an HTL.