Boosting charge-transfer in tuned Au nanoparticles on defect-rich TiO2 nanosheets for enhancing nitrogen electroreduction to ammonia production

The electrocatalytic nitrogen reduction reaction (eNRR) to ammonia (NH 3 ) has been recognized as an effective, carbon–neutral, and great-potential strategy for ammonia production. However, the conversion efficiency and selectivity of eNRR still face significant challenges due to the slow transfer kinetics and lack of effective N 2 adsorption and activation sites in this process. Herein, we designed and fabricated defect-rich TiO 2 nanosheets furnished with oxygen vacancies (OVs) and Au nanoparticles (Au/TiO 2-x ) as the electrocatalyst for efficient N 2 -fixing. The experimental results demonstrate that OVs act as active sites, which enable efficient chemisorption and activation of N 2 molecules. The Au nanoparticles loaded on the OVs-rich TiO 2 nanosheets not only accelerate charge transfer but also change the local electronic structure, thus enhancing N 2 adsorption and activation. In this work, the optimal Au/TiO 2-x electrocatalyst displays a considerable NH 3 yield activity of 12.5 μg h −1 mg cat. -1 and a faradaic efficiency (FE) of 10.2 % at −0.40 V vs reversible hydrogen electrode (RHE). More importantly, the Au/TiO 2-x exhibits a stable N 2 -fixing activity in cycling and it persists even after 80 h of consecutive electrolysis. Density functional theory (DFT) calculations reveal that the OVs serve as the active sites in TiO 2 , while Au nanoparticles are crucial for improving N 2 chemisorption and lowering the reaction energy barrier by facilitating the charge transfer for eNRR with a distal hydrogenation pathway. This research offers a rational catalytic site design for modulating charge transfer of active sites on metal-supported defective catalysts to boost N 2 electroreduction to NH 3 .