Two-Dimensional Nanomesh Arrays as Bifunctional Catalysts for N<sub>2</sub> Electrolysis
Yuntong Sun, Tianyu Jiang, Jingjing Duan, Lili Jiang, Xuemin Hu, Hongan Zhao, Junwu Zhu, Sheng Chen, Xin Wang
Abstract
N2 electrolysis has been impeded by efficient catalysts for key reactions: cathodic nitrogen reduction reaction (NRR) and anodic oxygen evolution reaction (OER). A bifunctional nickel, iron-nanomesh array electrocatalyst has been developed characteristic of excellent structural features for favorable NRR and OER processes, including highly exposed active sites originated from sub-nanometer-thick nanomeshes, hierarchical porosity resulting from the array-arranged nanolayers, and binary nickel, iron active sites. The electrode demonstrates excellent NRR activity with an ammonia yield of 16.89 μg h–1 mg–1cat and a faradaic efficiency (FE) of 12.50% at −350 mV (vs RHE), in addition to OER activity with a small overpotential of 191 mV to achieve 10 mA cm–2. Consequently, a full N2 electrolysis system has been constructed that exhibits remarkable ammonia production performance with an ammonia yield of 2.07 μg h–1 mg–1cat at 1.9 V, an FE of 9.87% at 1.6 V, and good durability for 30 h. Further mechanism study through density function theory shows that the NRR proceeds via an associative distal pathway, whereas the free energies for the N2* → NNH* intermediate step in the NRR as well as the OH* + H2O → O* + H2O intermediate step in the OER can be reduced by tuning the catalysts’ electronic structure by the strong synergistic effect between nickel and iron.