Plasmon-Driven Nitrogen Photoreduction to Ammonia Using Silica-Encapsulated Au Nanostar/TiO2 Nanohybrids

Identifier:  imarina:9462754

Handle: https://hdl.handle.net/20.500.11797/imarina9462754

Authors:  Negrín-Montecelo, Y; Sousa-Castillo, A; Cardeñoso-Garrido, N; Guillade, L; Besteiro, LV; Vázquez-González, M; Alvarez-Puebla, RA; Puértolas, B; Correa-Duarte, MA

Abstract:
Plasmon-induced photocatalysis has gained traction as a promising means to efficiently drive chemical reactions using light. In particular, photocatalytic N2 reduction emerges as a sustainable route to produce ammonia, a key starting material in the manufacture of nitrogen-rich fertilizers and a potential energy vector. Here, various Au nanoparticle morphologies combined with a TiO2 semiconductor are initially screened, and Au nanostar is identified as the most efficient morphology. Encasing this material within a mesoporous silica shell improved their stability and selectivity to ammonia formation, eliminating the need for hole scavengers. Advanced characterization including TEM and operando SERS spectroscopy together with the evaluation of the material in the presence of optical filters and probes reveal that the superior performance originates from the injection of excited "hot" charge carriers from the plasmonic material to the semiconductor, driving N2 reduction to NH3 under visible light. The wavelength-dependence experiments demonstrate a synergistic interaction between gold interband transitions and plasmonic effects, combined with the TiO2 semiconductor, which enhances catalytic performance across the spectrum. Importantly, hot holes generated at the plasmonic sites oxidize water into oxygen and subsequently to nitrates, maintaining charge balance in the photocatalyst. This dual functionality ensures effective charge circulation and sustainable performance across multiple cycles.