An efficient hole transfer pathway on hematite integrated by ultrathin Al2O3 interlayer and novel CuCoOx cocatalyst for efficient photoelectrochemical water oxidation

[Display omitted] •α-Fe2O3/Al2O3/CuCoOx was prepared as photoanode for PEC water splitting.•Ultrathin Al2O3 acted as passivation layer inhibits the charge recombination and reduces the surface states of Fe2O3.•CuCoOx cocatalyst reduces the overpotential for OER and improves the hole transport/trapping from Fe2O3.•The integration of Al2O3 and CuCoOx constructs an unobstructed holes transfer pathway for PEC activity.•α-Fe2O3/Al2O3/CuCoOx exhibits a 17.6-fold photocurrent density and 200 mV cathodic-shifted onset potential than Fe2O3. Highly photoelectrochemical water oxidation efficiency could be realized by means of efficient photogenerated holes transfer pathway and low-cost cocatalysts. Here, we have integrated an ultrathin Al2O3 layer and novel copper-cobalt oxide (CuCoOx) cocatalyst on α-Fe2O3 photoanode to construct unobstructed holes transfer pathway and improve PEC activity. The resultant α-Fe2O3/Al2O3/CuCoOx photoanode exhibits high photocurrent density of 2.23 mA/cm2 at 1.23 V versus the reversible hydrogen electrode (VRHE) and negative onset potential of 0.7 VRHE, which is about 17.6 times higher and 200 mV cathodic shift than bare α-Fe2O3 nanorod arrays. Detailed experimental results indicate the surface recombination passivation function of Al2O3 layer and improvement in charge separation and transfer kinetics of the role of low overpotential of CuCoOx with abundant oxygen vacancies for OER. The comparison discussion with CoOx and CuOx oxygen evolution catalysts (OECs) further illustrates the excellent catalytic performance of the CuCoOx. This work points to the effective utilization of novel but cheap CuCoOx OECs on photoanodes and provides a strategy for designing high activity photoanodes in photoelectrochemical water oxidation.