Thin films composed of Zr-doped In 2 O 3 grains rich in fracture surfaces and cracks for photoelectrochemical water oxidation.

Zr-doped In2 O3 thin films are prepared on FTO substrates by a two-step method: firstly, Zr-doped In(OH)3 thin films are hydrothermally deposited, and then converted to Zr-doped In2 O3 films by heat treatment. It is found that during the phase transition from Zr-doped In(OH)3 to Zr-doped In2 O3 , the cuboid-like crystal grains will fragment, resulting in a large number of new surfaces and cracks. Zr doping can introduce shallow impurity levels in the band gap of In2 O3 , which will enhance the absorption of incident light. The substitution of trivalent In3+ ions by tetravalent Zr4+ ions provides additional donors for In2 O3 , which reduces the charge transfer resistance of the photoelectrochemical water oxidation and thus improves the charge transfer kinetics. These factors synergistically improve the photoelectrochemical water oxidation performance of Zr-doped In2 O3 . For example, at a potential of 1.5 V versus reversible hydrogen electrode, the photocurrent density of the Zr-doped In2 O3 electrode during photoelectrochemical water splitting can be as high as about 3.5 times that of the undoped In2 O3 . Furthermore, Zr doping will also cause changes in the nucleation of some In(OH)3 grains, resulting in the formation of a small number of rod-bundle-shaped grains.