A highly efficient MoO x /Fe 2 O 3 photoanode with rich vacancies for photoelectrochemical O 2 evolution from water splitting

Photoelectrochemical O 2 evolution is the decisive step in photoelectrochemical water splitting. Among many photoanode materials, Fe 2 O 3 has attracted much attention for its ideal band gap and excellent light-absorption ability. However, surface defects and the easy recombination of photogenerated electron and hole pairs result in a low photoelectrochemical O 2 evolution activity from water splitting. In this study, the passivation layers of MoO x and oxygen vacancies were introduced on the surface of Fe 2 O 3 by a simple solvothermal treatment method, which could efficiently enhance photoelectrochemical O 2 evolution activity from water splitting. The MoO x /Fe 2 O 3 -3 sample showed the best photoelectrochemical O 2 evolution activity from water splitting. The photocurrent density of MoO x /Fe 2 O 3 -3 reached 3.3 mA cm −2 at 1.23 V vs. RHE, which was 5.6 times that of Fe 2 O 3 (0.58 mA cm −2 ). The passivation layer of MoO x was confirmed by HRTEM and XPS, while the presence of oxygen vacancies was confirmed by EPR and XPS. The passivation layers of MoO x and oxygen vacancies introduced could reduce the number of surface defects, increase the carrier density, enhance the injection efficiency of surface holes into the electrolyte, and promote the separation efficiency of photogenerated charges, leading to an improvement in the efficiency of photoelectrochemical oxygen production from water. This study provides a new idea and method for the development of photoelectrochemical O 2 evolution technology.