Fe2O3 hierarchical tubular structure decorated with cobalt phosphide (CoP) nanoparticles for efficient photoelectrochemical water splitting

Abstract

• Fabrication of large surface area and high crystallinity CoP/SnO 2 :Fe 2 O 3 HTS for PEC application. • The role of SnO 2 and CoP on the oxidation reaction kinetics in the photoanode system was proved. • The highest photocurrent density of 3.54 mA cm −2 at 1.23 V RHE among the Fe 2 O 3 -based photoanodes. Severe charge recombination and poor water oxidation kinetics limit the performance of hematite-based (Fe 2 O 3 ) photoanodes far from their theoretical levels and restrict their applicability for photoelectrochemical (PEC) water splitting devices. In this study, a hierarchical tubular structure (HTS) CoP/SnO 2 :Fe 2 O 3 with a large surface area and well-defined crystalline structures was fabricated via a facile template-engaged redox etching method. The SnO 2 nano-layer served as a dopant source to improve the bulk charge carrier transport efficiency along the Fe 2 O 3 HTS growth axis; therefore, the achieved photocurrent could be up to 2.0 mA cm −2 at 1.23 V RHE (V vs. reversible hydrogen electrode). The CoP nanoparticles (NPs) were introduced as a high-speed hole collector from the light-absorber layer as well as a catalyst to enhance charge carrier injection efficiency on the photoelectrode surface. As a result, CoP/SnO 2 :Fe 2 O 3 shows the highest photocurrent density of 3.50 mA cm −2 (at 1.23 V RHE ) with a negative shift in the onset potential of 180 mV.