Two-dimensional carbon nanosheets loaded with NiCo bimetallic catalysts for efficient electrocatalytic reduction of nitrogen to ammonia

Abstract

Ammonia, one of the most produced chemicals, is mainly produced by the Haber Bosch process, under high-temperature, high-pressure, and energy-intensive conditions. Therefore, electrocatalytic nitrogen reduction is an attractive alternative method under ambient conditions. In this paper, two-dimensional carbon nanosheets (CNS) are firstly prepared by a modified Hummer method, and then Co and Ni bimetal load on CNS are prepared by a hydrothermal method to investigate their electrocatalytic nitrogen reduction reaction (NRR) properties. CNS has a porous sheet structure, and the NiCo oxide nanoflower structure with zigzag folding grows on the surface of CNS, which is beneficial to improve the contact area of the catalyst with N2, increasing the number of active sites, and better improve the performance of N2 reduction NH3 synthesis. At −0.34 V, the NH3 yield reaches a maximum of 22.18 μg·h−1·mg−1, and the Faradaic efficiency (FE) is 4.50 %, both of which are about twice as high as that of pure CNS, which is superior to other metal-doped electrocatalysts used for N2 reduction. This study provides an effective method for the design of electrocatalysts with high N2 reduction performance for ammonia synthesis. The catalytic mechanism is further explored by the theoretical calculations of DFT.