Efficient Photocatalytic Nitrogen Fixation over Cuδ+-Modified Defective ZnAl-Layered Double Hydroxide Nanosheets

The photocatalytic reduction of nitrogen (N-2) with water (H2O) as the reducing agent holds great promise as a sustainable future technology for the synthesis of ammonia (NH3). Herein, the effect of oxygen vacancies and electron-rich Cu-delta(+) on the performance of zinc-aluminium layered double hydroxide (ZnAl-LDH) nanosheet photocatalysts for N-2 reduction to NH3 under UV-vis excitation is systematically explored. Results show that a 0.5%-ZnAl-LDH nanosheet photocatalyst (containing 0.5 mol% Cu by metal basis) affords a remarkable NH3 production rate of 110 mu mol g(-1) h(-1) and excellent stability in pure water. The X-ray absorption spectroscopy, electron paramagnetic resonance, and density functional theory calculations reveal that Cu addition imparts oxygen vacancies and coordinatively unsaturated Cu-delta(+) (delta < 2) with electron-rich property in the ZnAl-LDH nanosheets, both of which readily contribute to efficient separation and transfer of photogenerated electrons and holes and promote N-2 adsorption, thereby both activating N-2 and facilitating its multielectrons reduction to NH3.