Structural regulation and oxygen evolution reaction mechanism of coherent grain boundary-engineered B-ZnO@ZnS array photoanodes

The practical deployment of Zinc oxide (ZnO) photoanodes for photoelectrochemical (PEC) water splitting is severely impeded by rapid photogenerated carrier recombination and sluggish oxygen evolution reaction (OER) kinetics. Herein, we elucidate a synergistic structural engineering strategy integrating interstitial boron (B) doping, Type-II heterojunction construction, and coherent grain boundary regulation to tailor high-performance B-ZnO@ZnS nanorod arrays. Comprehensive characterizations corroborate that B-doping introduces abundant oxygen vacancies to modulate the electronic band structure, while the coherent B-ZnO/ZnS interface establishes a robust built-in electric field, thereby facilitating bulk charge separation and accelerating interfacial hole transfer. Consequently, the optimized photoanode exhibits a remarkable photocurrent density of 1.054 mA cm −2 at 1.23 V vs. RHE (representing a 1.67-fold enhancement over pristine ZnO) and a substantial cathodic shift in onset potential to 0.24 V. Notably, in situ ATR-IR spectroscopy captures the dynamic evolution of key *OOH intermediates, corroborating an adsorption evolution mechanism (AEM) where the multidimensional engineering significantly ameliorates the energy barrier for intermediate formation. This work offers a pivotal paradigm for designing durable and high-efficiency photoelectrodes via precise defect and interface manipulation.