Defective indium oxide as plasmonic catalyst for efficient photo-driven methanol steam reforming.

Expanding plasmonic catalysis from noble metals to earth-abundant oxides is important for sustainable solar-to-chemical conversion, but mechanisms remain poorly understood. Here, we show that lithium-reduction-induced defects modulate the electronic structure of indium oxide, increasing free-carrier concentration 2.5-fold and producing a near-infrared plasmon-like response. Computational and spectroscopic analyses suggest that oxygen vacancies act as preferential hot-electron traps, enhance near fields, and shift the kinetically sensitive step from methoxy dehydrogenation on pristine surfaces to intermediate dehydrogenation on defective surfaces. Injection of plasmon-induced hot electrons into intermediate antibonding orbitals may reduce the apparent activation energy from 75.7 to 27.8 kJ mol-1. In this work, we report a competitive methanol steam reforming catalyst with a hydrogen production rate of 214 μmol gcat-1 s-1 and show how defect and electronic engineering can tailor oxide-based plasmonic systems.