2D Co-incorporated hydroxyapatite nanoarchitecture as a potential efficient oxygen evolution cocatalyst for boosting photoelectrochemical water splitting on Fe2O3 photoanode

The serious charge recombination together with the sluggish water oxidation kinetics have largely limited the practical application of hematite (Fe2O3) in photoelectrochemical (PEC) water splitting. Surface modification with oxygen evolution cocatalyst is an efficient strategy to address the both issues. Herein, a novel 2D oxygen evolution cocatalyst, namely Co-incorporated hydroxyapatite (Co-HAP) nanoarchitecture, was rationally designed and decorated on Fe2O3 photoanode. The resulting Co-HAP decorated Fe2O3 (Co-HAP/Fe2O3) exhibited excellent PEC water splitting with a high photocurrent density of 2.25 mA cm(-2) at 1.23 V vs. RHE in neutral electrolyte, which is ca. 9.78 times that for bare Fe203. Moreover, the onset potential displayed a 200 mV cathodic shift, indicating an accelerated water oxidation kinetics over Fe2O3. PEC characterizations revealed Co-HAP could not only significantly improve the charge-separation efficiency but also could enhance the surface charge-separation efficiency in the bulk and on the surface of Fe2O3. Comprehensive investigations unveiled the interfacial negative electrostatic field and the increased electrical conductivity arising from Co-HAP decoration were of great benefit to improve the charge separation and inhibit surface charge recombination, while the 2D architecture of Co-HAP offered high surface area and abundant exposed Co active sites, ultimately boosted PEC water splitting over Fe203. Owing to the superior ion-exchange ability of HAP, the strategy presented here would open a new vane to explore highly efficient oxygen evolution cocatalyst.