Atomically Precise Dinuclear Ni<sub>2</sub> Active Site-Modified MOF-Derived ZnO@NC Heterojunction toward High-Performance N<sub>2</sub> Photofixation
Wensheng Zhang, Tianren Liu, Qingmei Tan, Jianshen Li, Yuangong Ma, Ying He, Dongxue Han, Dongdong Qin, Li Niu
Abstract
The development of heterogeneous catalysts with atom-dispersed active sites is essential to facilitate nitrogen (N 2 ) activation for the N 2 reduction reaction (NRR). However, it remains a major challenge to tune the coordination configuration of the metal centers to further accelerate the activation kinetics. Herein, an atomically precise dinuclear Ni 2 site-modified metal–organic framework (MOF)-derived ZnO@NC heterojunction (ZnO@NC-Ni 2 ) was developed for effective N 2 photofixation under mild conditions. Moreover, advanced structural characterization indicates that the most active N-coordinated bimetallic site configurations are Ni 2 –N 6, where two Ni 1 –N 4 moieties are shared with two N atoms. Theoretical calculations further demonstrate that the binuclear Ni 2 active sites of ZnO@NC-Ni 2 could adjust the N 2 adsorption configuration as the side-on bridging adsorption mode (denoted as “*N≡N*”), while the single metal Ni 1 sites of ZnO@NC-Ni 1 tend to form a terminal adsorption configuration with N 2 (“*N≡N” type). As a result, the unique electronic structure of binuclear Ni 2 active sites in ZnO@NC-Ni 2 tends to proceed as an associative alternating pathway, thereby decreasing the activation energy barrier of the reaction procedure and favoring the photocatalytic NRR. The present study provides a perspective to probe the relationship between the coordination architecture of earth-abundant metal active centers and NRR activities.