Boosting charge-transfer in tuned Au nanoparticles on defect-rich TiO2 nanosheets for enhancing nitrogen electroreduction to ammonia production
Peng Yang, Heng Guo, Haoran Wu, Fengying Zhang, Jiaxin Liu, Mengyue Li, Yuantao Yang, Yuehan Cao, Guidong Yang, Ying Zhou
Abstract
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 .