Synergistic engineering of heteronuclear Ni-Ag dual-atom catalysts for high-efficiency CO2 electroreduction with nearly 100% CO selectivity

Abstract

Single-atom catalysts (SACs) have emerged as attractive materials for the electrocatalytic carbon dioxide reduction (ECO2R). Dual-atom catalysts (DACs), an extension of SACs, exhibit more compelling functionalities due to the synergistic effects between adjacent metal atoms. However, the rational design, clear coordination mode, and in-depth understanding of heteronuclear dual-atom synergistic mechanisms remain elusive. Herein, a heteronuclear Ni-Ag dual-atom catalyst loaded on defective nitrogen-rich porous carbon, denoted as Ni-Ag/PC-N, was synthesized using cascade pyrolysis. The configuration of Ni-Ag dual-atom sites is confirmed as N3-Ni-Ag-N3. Ni-Ag/PC-N demonstrates a remarkable CO Faradaic efficiency (FECO) exceeding 90% over a broad range of applied potentials, i.e., from −0.7 to −1.3 V versus reversible hydrogen electrode (RHE). The peak FECO of 99.2% is observed at −0.8 V (vs. RHE). Tafel analysis reveals that the rate-determining step of ECO2R-to-CO is the formation of the *COOH intermediate, and Ni-Ag/PC-N exhibits optimal electrokinetics. In situ FTIR and in situ Raman spectra indicate accelerated production of *COOH intermediates during the ECO2R-to-CO process. Density functional theory (DFT) calculations demonstrate that the coordinated Ni atom lowers the energy barrier of *COOH intermediates formation over the Ni-Ag/PC-N surface, while the adjacent Ag atom mitigates the catalyst poisoning caused by the strong *CO affinity on the Ni atomic site.