Ni single-atom sites supported on carbon aerogel for highly efficient electroreduction of carbon dioxide with industrial current densities

Finding highly efficient electrocatalysts for the CO2 electroreduction reactions (CO2RR) that have high selectivity and appreciable current density to meet commercial application standards remains a challenge. Because their reduction potentials are similar to that of the associated competitive hydrogen evolution reaction and the CO2 activation kinetics are sluggish. Although single-atom catalysts (SACs) with high atom efficiency are one class of promising candidates for the CO2RR to produce CO, single-atom active sites supported on microporous carbons are not fully exposed to substrates and thus lead to low current density. Carbon aerogels with interconnected channels and macropores can facilitate mass transport. But few reports describe utilizing them as supports to anchor SACs for efficient electrocatalysis. Herein, N-doped carbon aerogels supporting Ni single atomic catalyst sites (denoted as Ni-NCA-X, X ​= ​10, 20) were fabricated by pyrolyzing Ni/Zn bimetallic zeolitic imidazolate framework (Ni/Zn-ZIF-8)/carboxymethylcellulose composite gels. Owing to abundant hierarchical micro-, meso-, and macropores and high CO2 adsorption, the Ni single active sites in the optimal Ni-NCA-10 were readily accessible for the electrolyte and CO2 molecules and thus achieved an industrial-level CO partial current density of 226 ​mA ​cm−2, a high CO Faradaic efficiency of 95.6% at −1.0 ​V vs. the reversible hydrogen electrode, and a large turnover frequency of 271810 h−1 in a flow-cell reactor at −1.0 ​V. Such excellent CO2RR performance makes Ni-NCA-10 a rare state-of-the-art electrocatalyst for CO2-to-CO conversion. This work provides an effective strategy for designing highly efficient electrocatalysts toward the CO2RR to achieve industrial current density via anchoring single-atom sites on carbon aerogels. N-doped carbon aerogels were fabricated to maximize the accessibility of the Ni single atomic sites for CO2 molecules and electrolytes and facilitate in mass transfer, thereby enhance the electrocatalytic performance of CO2 reduction reaction. The optimal Ni-NCA-10 achieves an industrial level CO partial current density of 226 ​mA ​cm−2, high CO Faradaic efficiency of 95.6% at −1.0 ​V vs. reversible hydrogen electrode (RHE) and large turnover frequency (TOF) of 271810 ​h−1 in a flow-cell reactor at −1.0 ​V. [Display omitted] •Ni single-atom sites supported on carbon aerogel catalysts (Ni-NCA) were fabricated by pyrolysis of Ni/Zn-ZIF-8/CMC.•Ni-NCA have abundant hie