NiO Nanoparticles Anchored on Phosphorus-Doped α-Fe2O3 Nanoarrays: An Efficient Hole Extraction p–n Heterojunction Photoanode for Water Oxidation

Graphical Dope to promote : A high-performance photoanode consisting of NiO nanoparticles anchored on a gradient P-doped α-Fe 2 O 3 nanorod array (NiO/P-α-Fe 2 O 3 ) is successfully fabricated. The electrochemical results show that the photoanode presents a high photocurrent density and long-term stability for improved water oxidation. The photoelectrochemical (PEC) water-splitting efficiency of a hematite-based photoanode is still far from the theoretical value due to its poor surface reaction kinetics and high density of surface trapping states. To solve these drawbacks, a photoanode consisting of NiO nanoparticles anchored on a gradient phosphorus-doped α-Fe 2 O 3 nanorod (NR) array (NiO/P-α-Fe 2 O 3 ) was fabricated to achieve optimal light absorption and charge separation, as well as rapid surface reaction kinetics. Specifically, a photoanode with the NR array structure allowed a high mass-transport rate to be achieved, while phosphorus doping effectively decreased the number of surface trapping sites and improved the electrical conductivity of α-Fe 2 O 3 . Furthermore, the p–n junction that forms between NiO and P-α-Fe 2 O 3 can further improve the PEC performance due to efficient hole extraction and the water oxidization catalytic activity of NiO. Consequently, the NiO/P-α-Fe 2 O 3 NR photoanode produced a high photocurrent density of 2.08 mA cm −2 at 1.23 V versus a reversible hydrogen electrode and a 110 mV cathodic shift of the onset potential. This rational design of structure offers a new perspective in exploring high-performance PEC photoanodes.