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

Abstract Severe charge recombination and poor water oxidation kinetics limit the performance of hematite-based (Fe2O3) 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/SnO2:Fe2O3 with a large surface area and well-defined crystalline structures was fabricated via a facile template-engaged redox etching method. The SnO2 nano-layer served as a dopant source to improve the bulk charge carrier transport efficiency along the Fe2O3 HTS growth axis; therefore, the achieved photocurrent could be up to 2.0 mA cm-2 at 1.23 VRHE (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/SnO2:Fe2O3 shows the highest photocurrent density of 3.50 mA cm-2 (at 1.23 VRHE) with a negative shift in the onset potential of 180 mV.