Revealing the Kinetic Balance between Proton-Feeding and Hydrogenation in CO2 Electroreduction

Electrocatalytic reduction of CO2 to high-value-added chemicals provides a feasible path for global carbon balance. Herein, the fabrication of Ni-NP(x)@Ni-SA(y)-NG (x,y = 1, 2, 3; NG = nitrogen-doped graphite) is reported, in which Ni single atom sites (Ni-SA) and Ni nanoparticles (Ni-NP) coexist. These Ni-NP(x)@Ni-SA(y)-NG presented a volcano-like trend for maximum CO Faradaic efficiency (FECO) with the highest point at Ni-NP2@Ni-SA2-NG in CO2RR. Ni-NP2@Ni-SA2-NG exhibited approximate to 98% of maximum FECO and a large current density of -264 mA cm(-2) at -0.98 V (vs. RHE) in the flow cell. In situ experiment and density functional theory (DFT) calculations confirmed that the proper content of Ni-SA and Ni-NP balanced kinetic between proton-feeding and CO2 hydrogenation. The Ni-NP in Ni-NP2@Ni-SA2-NG promoted the formation of H* and reduced the energy barrier of *CO2 hydrogenation to *COOH, and CO desorption can be efficiently facilitated by Ni-SA sites, thereby resulting in enhanced CO2RR performance.

Automated summary

The fabrication of Ni-NP(x)@Ni-SA(y)-NG (x,y = 1, 2, 3; NG = nitrogen-doped graphite) materials with coexistence of Ni single atom sites (Ni-SA) and Ni nanoparticles (Ni-NP) is reported for electrocatalytic reduction of CO2. Ni-NP2@Ni-SA2-NG exhibited approximately 98% maximum CO Faradaic efficiency (FECO) and a large current density of -264 mA cm(-2) at -0.98 V (vs. RHE) in the flow cell. In situ experiment and density functional theory (DFT) calculations confirmed that the proper content of Ni-SA and Ni-NP balanced kinetic between proton-feeding and CO2 hydrogenation, leading to enhanced CO2RR performance.