Rational Fabrication of Low-Coordinate Single-Atom Ni Electrocatalysts by MOFs for Highly Selective CO2 Reduction

Single-atom catalysts (SACs) have attracted tremendous interests due to their ultrahigh activity and selectivity. However, the rational control over coordination microenvironment of SACs remains a grand challenge. Herein, a post-synthetic metal substitution (PSMS) strategy has been developed to fabricate single-atom Ni catalysts with different N coordination numbers (denoted Ni-N-x-C) on pre-designed N-doped carbon derived from metal-organic frameworks. When served for CO2 electroreduction, the obtained Ni-N-3-C catalyst achieves CO Faradaic efficiency (FE) up to 95.6 %, much superior to that of Ni-N-4-C. Theoretical calculations reveal that the lower Ni coordination number in Ni-N-3-C can significantly enhance COOH* formation, thereby accelerating CO2 reduction. In addition, Ni-N-3-C shows excellent performance in Zn-CO2 battery with ultrahigh CO FE and excellent stability. This work opens up a new and general avenue to coordination microenvironment modulation (MEM) of SACs for CO2 utilization.

Automated summary

A single-atom Ni catalyst with different N coordination numbers was fabricated using a post-synthetic metal substitution strategy. The Ni-N-3-C catalyst showed significantly enhanced COOH* formation leading to accelerated CO2 reduction, achieving high CO Faradaic efficiency and excellent performance in Zn-CO2 battery. This work provides a new approach for modulation of coordination microenvironment in single-atom catalysts for CO2 utilization.