Enhanced photocatalytic N2 fixation via defective and fluoride modified TiO2 surface

Oxygen vacancy (Vo) and F are introduced on the TiO2 nanoparticle surface. Vo enhances charge separation efficiency, chemical adsorption and activation of N2 molecules. F modification alter the wettability of surface, which enrich the N2 physical adsorption on the surface resulting in high local N2 concentration. These are beneficial for the enhancement of N2 fixation. [Display omitted] •F capped TiO2 surface convert the hydrophilic nature to aerophilic nature to enrich the N2 at the surface of catalyst.•Surface oxygen vacancies promote the chemisorption of N2 molecule on the TiO2 surface.•Surface oxygen vacancies enhance the trapped electron transfer from the catalyst to the adsorbed N2 molecules. Photocatalytic N2 fixation (PNF) provides a low-cost route to generate ammonia. The poor conversion efficiency from photon to ammonia seriously hinders the step forward because of the low concentration of N2 molecules. Herein, we demonstrate a photocatalyst with surface oxygen vacancies (Vo) and a F modified surface to facilitate N2 adsorption and activation on the surface of catalysts. The Vo site promotes the chemical adsorption of N2, electron transfer from catalyst to N2. F modification switches the TiO2 surface properties from hydrophilic to aerophilic, thus facilitating the adsorption of N2. Meanwhile, the hydrogen reduction reaction (HER) is suppressed, as protons hard to adsorb on F capped surfaces. The optimal NH3 production rate can reach 206 μmolh−1g−1, which is ∼ 9 times higher than that of pure TiO2 nanoparticles (∼23 μmolh−1g−1). This report provides a potential strategy to overcome mass transfer limitation and achieve a high conversion efficiency in PNF.