CoMoO₄-modified hematite with oxygen vacancies for high-efficiency solar water splitting

Hematite is a potential photoelectrode for photoelectrochemical (PEC) water splitting. Nevertheless, its water oxidation efficiency is highly limited by its significant photogenerated carrier recombination, poor conductivity and slow water oxidation kinetics. Herein, under low-vacuum (LV) conditions, we fabricated a CoMoO₄ layer on oxygen-vacancy-modified hematite (CoMo-Fe₂O₃ (LV)) for the first time for efficient solar water splitting. The existence of oxygen vacancies can significantly facilitate the electrical conductivity, while the large onset potential along with oxygen vacancies can be lowered by the CoMoO₄ with accelerated water oxidation kinetics. Therefore, a high photocurrent density of 3.53 mA cm^-2 at 1.23 V_RHE was obtained for the CoMo-Fe₂O₃ (LV) photoanode. Moreover, it can be further coupled with the FeNiOOH co-catalyst to reach a benchmark photocurrent of 4.18 mA cm^-2 at 1.23 V_RHE, which is increased around 4-fold compared with bare hematite (0.90 mA cm^-2). The combination of CoMoO₄, FeNiOOH, and oxygen vacancies may be used as a reasonable strategy for developing high-efficiency hematite-based photoelectrodes for solar water oxidation.