A highly efficient photoelectrochemical cell using cobalt phosphide-modified nanoporous hematite photoanode for solar-driven water splitting

Abstract

Developing an efficient and stable photoanode based on inexpensive and earth-abundant materials is a great challenge for water splitting. Herein we report for the first time the use of cobalt phosphide (CoP) as a highly active cocatalyst on hematite photoanode for high-performance photoelectrochemical water splitting. CoP nanoparticles can be deposited on a bilayer Ti-doped porous hematite (Ti-PH) photoanode by a facile drop-casting method. The results show that CoP can significantly increase the hole injection efficiency and reduce the charge transport resistance (Rct) in the Ti-PH. Under optimal conditions, the as-prepared CoP modified Ti-PH photoanode exhibits excellent and stable photoelectrochemical water oxidation performance with a current density of 2.1 mA/cm2 at 1.23 V vs. RHE, which is among the best values using noble-metal-free hematite-based photoanodes for water splitting. At an applied bias of 1.23 V vs. RHE, the hole injection efficiency of Ti-PH/CoP is ∼90%, which is close to 96% at a higher potential. The IPCE value of optimal Ti-PH/CoP can reach to 40.3% at 1.23 V versus RHE (at 380 nm). In addition, the photocurrent onset potential cathodically shifted by ∼180 mV compared to Ti-doped hematite photoanode under AM 1.5G illumination (100 mW/cm2).