Constructing the Vo-TiO2/Ag/TiO2 Heterojunction for Efficient Photoelectrochemical Nitrogen Reduction to Ammonia

Abstract

Photoelectrochemical (PEC) nitrogen (N2) fixation technology provides the possibility to produce ammonia (NH3) under mild conditions, but the efficiency of N2 reduction in this process is greatly limited due to the high bond energy and ionic potential of N2. Herein, the Vo-TiO2/Ag/TiO2 photoelectrode consisting of rutile TiO2 nanorod arrays, Ag nanoparticles, and anatase TiO2 nanosheets with oxygen vacancies (Vo-TiO2) was constructed for accelerating the PEC reduction of N2 into ammonia. The separation of photogenerated carriers can be promoted by the heterojunction among TiO2 nanorods, Ag nanoparticles, and Vo-TiO2 nanosheets. Furthermore, the photogenerated electrons from the conduction band of TiO2 and the hot electrons from Ag nanoparticles’ local surface plasmon resonance (LSPR) effect were injected into the conduction band of Vo-TiO2, and they were further captured by Vo-TiO2 oxygen vacancy and can reduce N2 that adsorbed on the catalyst to NH3. Without any sacrificial agent, the average NH3 production rate can reach 51.2 μg h–1 cm–2. The catalyst exhibited excellent stability even after multiple uses. The LSPR effect of Ag nanoparticles and heterojunction structure promote the better PEC performance of TiO2 nanorod arrays.