Changing charge transfer mode with cobalt-molybdenum bimetallic atomic pairs for enhanced nitrogen fixation

作者：Li, Xin; Liu, Jin; Zhang, Yizhen; Leung, Michael K. H.^*

来源：Journal of Materials Chemistry A, 2022, 10(29): 15595-15604.

DOI：10.1039/d2ta02455a

• HYDROGEN EVOLUTION REACTION
• DOPED POROUS CARBON
• OXYGEN REDUCTION
• EFFICIENT ELECTROCATALYST
• SINGLE
• CATALYSTS
• N-2
• GRAPHENE
• SITES
• COORDINATION

The single-atom catalyst is currently regarded as a promising electrocatalyst for the electrochemical reduction of N-2 to NH3 but its development is impeded by the sluggish kinetics of the proton-coupled electron transfer on the unitary single-atom site. To address this issue, we developed a novel type of electrocatalyst with atomically dispersed Co-Mo pairs anchored on N-doped carbon frameworks (Co-Mo-SA/NC). Remarkably, the theoretical calculations reveal that the formation of Co-Mo asymmetric bimetallic active sites not only changes the "acceptance-donation" charge transfer mode on a single active site to "donation-donation" mode but also modifies the d-band center of the corresponding single atom, leading to enhanced polarization of the N N triple bond and inhibition of the hydrogen evolution reaction. As a result, the Co-Mo-SA/NC catalyst achieves a high ammonia yield rate of 37.73 mu g h(-1) mg(cat)(-1) and a desirable faradaic efficiency of 23.18% at -0.1 V versus the reversible hydrogen electrode, which are twofold higher than those of the isolated single-atom Co (Co-SA/NC) or Mo (Mo-SA/NC) catalyst. This study provides a promising new strategic design of an electrocatalyst using atomically dispersed metal-pairs to enhance electrochemical nitrogen fixation.