Tailoring the local catalytic microenvironment of metal centers NH2 groups to enhance the CO2RR performance of Ni based catalysts
Efficient catalytic reduction of the main greenhouse gas CO 2 into high value-added chemicals is an important measure to alleviate the greenhouse effect and energy depletion. Metal nitrogen (M-N 4 ) macrocyclic complexes have attracted increasing attention in the field of electrocatalytic CO 2 reduction (CO 2 RR) due to the precise adjustment of the catalytic active site according to the requirements and the flexible modification of the external ligand structure. Nevertheless, the poor activity and low selectivity of reduction products restrict their widespread application in electrocatalytic CO 2 RR. Herein, a combination of nanoscale and molecular level method has been developed to construct easily obtainable 4NH 2 -NiPc/NH 2 -CNT hybrid material, in which amino groups are connected to provide electrons toward the central Ni-N 4 site to promote the electrocatalytic CO 2 RR catalytic activity. As a result, the catalyst 4NH 2 -NiPc/NH 2 -CNT mainly produces CO in the electrocatalytic CO 2 RR, which exhibits a Faradaic efficiency of CO (FE CO ) higher than 92 % within a wide overpotential range of −0.70 to −0.95 V vs. RHE, and provides excellent stability with a current density of 12 mA cm −2 at −0.80 V vs. RHE. In addition, 4NH 2 -NiPc/NH 2 -CNT reaches its maximum FE CO value of 96 % at −0.8 V vs. RHE, which is approximately 3.1 times that of the original unmodified NiPc/CNT, demonstrating excellent promotion of electrochemical performance. Similarly, compared to NiPc/CNT without amino modification, the current density of 4NH 2 -NiPc/NH 2 -CNT exceeds it by more than twice. The research results indicate that promoting role of electron substituted amino groups in catalysis dispersion and electronic environment coordination. This study proposes a promising strategy of introducing amino groups into molecular catalysts and hybridizing with carbon nanotube to enhance the electrocatalytic conversion of CO 2 to deep reduction products.
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