Metal Oxide Clusters on Nitrogen-Doped Carbon are Highly Selective for CO₂ Electroreduction to CO

Abstract

The electrochemical reduction of CO2 (eCO2RR) using renewable energy is an effective approach to pursue carbon neutrality. The eCO2RR to CO is indispensable in promoting C–C coupling through bifunctional catalysis and achieving cascade conversion from CO2 to C2+. This work investigates a series of M/N–C (M = Mn, Fe, Co, Ni, Cu, and Zn) catalysts, for which the metal precursor interacted with the nitrogen-doped carbon support (N–C) at room temperature, resulting in the metal being present as (sub)­nanosized metal oxide clusters under ex situ conditions, except for Cu/N–C and Zn/N–C. A volcano trend in their activity toward CO as a function of the group of the transition metal is revealed, with Co/N–C exhibiting the highest activity at −0.5 V versus RHE, while Ni/N–C shows both appreciable activity and selectivity. Operando X-ray absorption spectroscopy shows that the majority of Cu atoms in Cu/N–C form Cu0 clusters during eCO2RR, while Mn/, Fe/, Co/, and Ni/N–C catalysts maintain the metal hydroxide structures, with a minor amount of M0 formed in Fe/, Co/, and Ni/N–C. The superior activity of Fe/, Co/, and Ni/N–C is ascribed to the phase contraction and the HCO3 – insertion into the layered structure of metal hydroxides. Our work provides a facile synthetic approach toward highly active and selective electrocatalysts to convert CO2 into CO. Coupled with state-of-the-art NiFe-based anodes in a full-cell device, Ni/N–C exhibits >80% Faradaic efficiency toward CO at 100 mA cm–2.

Keeping sight of copper in single-atom catalysts for electrochemical carbon dioxide reduction

“…SACs incorporating metals other than Cu can also undergo agglomeration, however, the degree of M 0 formation is typically much lower than that of Cu-SACs and often not reversible 20 , 21 . Therefore, the possible causes behind cluster formation and the reversibility of this process must be understood through assessment of specific Cu-based examples.…”

Supported Sub‐Nanometer Clusters for Electrocatalysis Applications

“…As a result, the optimized catalyst displays a superior bifunctional oxygen electrocatalysis performance with a small potential gap of 0.67 V. A series of sub‐nanometer transition metal (Mn, Fe, Co, and Ni) hydroxide clusters loaded on N‐doped carbon support were synthesized and studied in CO 2 RR. [ 87 ] It found that Fe‐, Co‐, and Ni‐based hydroxide clusters display high activity and selectivity toward CO 2 to CO conversion, which is attributed to the phase‐contraction of metal hydroxide clusters with HCO 3 − insertion.…”

Highly Dispersed NiO Clusters Induced Electron Delocalization of NiNC Catalysts for Enhanced CO2 Electroreduction

“…Recently, Li et al [ 27 ] studied a series of M/NC catalysts characterized by N‐doped carbon hosting highly dispersed metal oxide particles, where the Ni/NC sample showed high activity and selectivity for CO 2 RR. Their findings suggest that a synergy between (sub)‐nano metal oxide clusters and N defects or MN x are key to the high performance of M/NC catalysts.…”