Preparation of ZnO p-n homojunction nanorod via nitrogen ion injection coupled with Au induced SPR effect for enhanced photoelectrochemical water splitting

The photoelectrochemical (PEC) water splitting, which employs catalytic semiconductors to convert solar energy into hydrogen, is a promising approach for achieving securer and sustainable energy supply. Nanostructured ZnO have exhibited excellent PEC properties but the bottlenecks of limited visible-light response and poor electron -hole separation hindered their applications. In this work, nitrogen ions were injected into dense ZnO nanoarrays, which was hydrothermally grown on Au-NPs sputtered ITO substrate. The injected nitrogen preferably occupied oxygen vacancies in pristine ZnO, leading to the in-sit transition of p-ZnO and formation of p-n homojunctions. Benefiting from the surface plasmon resonance effect of Au and the internal electric field (IEF) of p-n homo-junctions, full-spectrum light absorption and effective cross-interface carrier separation was achieved. The photocurrent density and hydrogen production rate of injected photoelectrode reaches 2.38 mA cm-2 and 4.56 mM cm-2 h-1, which is 21.64 and 7.35 times higher than that of pure-ZnO respectively. This PEC enhancement was attributed to the uniformly sputtered Au coupled with ZnO p-n homojunctions, which synergistically boosted light harvesting efficiency and suppress carrier recombination. This work contributes to the rational design of PEC photoelectrode via combining full-spectrum light absorption promoter with p-n homojunction induced IEF to harvest solar energy into chemical forms.