Enhanced photoelectrochemical water oxidation in Hematite: Accelerated charge separation with Co doping

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The nanoparticle Co-doped Fe 2 O 3 shows an increase in photocurrent density by 23 times than pristine α-Fe 2 O 3 and reaches 0.54 mA/cm 2 at 1.23 V RHE . While, the onset potential also negatively shifts by about 290 mV to 0.62 V RHE . • The preparation method of Co doped α-Fe 2 O 3 was successfully developed. • The photocurrent density and onset potential were both improved. • Charge separation efficiency was enhanced. • The Co 2+ /Co 3+ on the surface of Fe 2 O 3 accelerated the oxygen evolution kinetics. Hematite (α-Fe 2 O 3 ) is one of the most promising candidates for a photoanode for photoelectrochemical water splitting. However, it has low efficiency because of poor conductivity in the bulk and sluggish oxygen evolution (OER) kinetics on the surface. In this study, a Co-doped α-Fe 2 O 3 photoanode was prepared by the hydrothermal method. It had increased charge separation efficiency and accelerated surface reaction kinetics simultaneously. At the optimal Co content, the photocurrent density of the Co-doped α-Fe 2 O 3 increased by 23 times to 0.54 mA/cm 2 at 1.23 V RHE in 1 M NaOH electrolyte; this increase was attributed to the improvement in carrier density and charge transfer behavior. Moreover, the cathodic shift of onset potential for Co-doped α-Fe 2 O 3 reached 290 mV owing to the accelerated OER kinetics. This work reveals the key roles of Co doping and provides a suitable photoanode for solar hydrogen technology.