Hierarchical Ni/N/C Single‐Site Catalyst Achieving Industrial‐Level Current Density and Ultra‐Wide Potential Plateau of High CO Faradic Efficiency for CO₂ Electroreduction

Abstract

The practical applications of CO 2 electroreduction to CO driven by renewable electricity should simultaneously meet the requests of industrial-level CO partial current density (J CO ) at least 100 mA cm −2 , wide potential window of high CO faradic efficiency (FE CO ), and low cost. Herein, a new strategy is reported to construct porous hierarchical Ni/N/C single-site catalyst with excellent catalytic activity via coating Ni-containing ZIF-8 on mesostructured basic magnesium carbonate template followed by pyrolysis. The abundant micropores facilitate the formation of numerous edge-hosted Ni-N 4 sites with high intrinsic activity, and the interconnected macro/mesopores much promote CO 2 delivery and CO release for the full expression of intrinsic activity. Consequently, the catalyst exhibits the industrial-level J CO of 105-462 mA cm −2 at the potential range of −0.6∼−1.3 V with ultra-wide high FE CO plateau (>90%@−0.4∼−1.3 V), showing great promise for practical application. This study provides a general synthetic strategy to explore high-performance hierarchical M/N/C electrocatalysts.

Facile Synthesis of Hierarchically Porous Ni–N–C for Efficient CO2 Electroreduction to CO

“…Notably, we calculated the TOF (calculation details in the Experimental Section) under different potentials. As shown in Figure d, the TOF of HP-Ni-NC-2 reaches 3003 h –1 at −0.9 V (vs RHE), which is comparable to that of some reported catalysts for CO 2 electrochemical reduction to CO. ,,,− …”

“…The chemical states and surface compositions of all catalysts were analyzed by XPS. As shown in Figure c, the Ni 2p spectrum of HP-Ni-NC-2 displays two peaks at 855.7 eV (2p 3/2 ) and 872.8 eV (2p 1/2 ), which are negative compared to the binding energy of Ni 2+ but positive compared to that of Ni 0 , indicative of the existence of the oxidation state of Ni δ+ (0 < δ < 2) in HP-Ni-NC-2 catalyst. , The chemical states of Ni species in HP-Ni-NC-4 and Ni-NC-2 are similar to that in HP-Ni-NC-2 (Figures S9 and S10). The N 1s spectra of all catalysts are presented in Figures d and S11–S13.…”

“…Although noble metal-based catalysts have exhibited satisfactory catalytic activity for CO generation, their high cost and scarcity hinder their commercial-scale application. − Recently, various types of nonprecious metal catalysts have been developed for CO 2 electroreduction to CO, including metal oxides and carbon-based nanomaterials. − Among them, metal/nitrogen-doped carbon (M–N x –C) nanostructures have gained considerable attention owing to their well-defined structure, maximum atom-utilization efficiency, and tailorable coordination environment. , Especially, Ni–N–C single-site catalysts exhibit high selectivity for CO production. − For example, Han et al fabricated atomic dispersed Ni–N 3 sites decorated on N-doped carbon for the CO 2 RR, achieving a CO Faradaic efficiency (FE) of 95.6% and a CO partial current density of 19.6 mA cm –2 at −1.0 V (vs RHE). Wang et al reported that a low-coordination Ni SA @N 3 –C catalyst exhibited 99.2% CO FE when the current density is −160 mA cm –2 .…”

Hierarchical Dual Single-Atom Catalysts with Coupled CoN4 and NiN4 Moieties for Industrial-Level CO2 Electroreduction to Syngas

“…32,33 Moreover, our recent reports have shown that constructing porous hierarchical catalysts can facilitate the charge/mass transfer kinetics to boost the expression of electrocatalytic activity. 34,35 Herein, by DFT optimization of metal species in M−N−C catalysts, the edge-hosted NiN…”

“…To achieve the industrial-level current density, the metal active sites should be first optimized to possess the best intrinsic activity of the CO 2 RR to CO or HER, and on the other side, the catalyst structure should be designed to facilitate charge/mass synergic transfer for fully expressing the catalytic activity. As is known, density functional theory (DFT) is a powerful tool to search the active MN x moieties to electrocatalytic reactions with suitable descriptors, which could be adopted to optimize the active species for syngas production. , Moreover, our recent reports have shown that constructing porous hierarchical catalysts can facilitate the charge/mass transfer kinetics to boost the expression of electrocatalytic activity. , Herein, by DFT optimization of metal species in M–N–C catalysts, the edge-hosted NiN 4 and CoN 4 configurations with the respective most-active CO 2 RR to CO and HER performances are screened out to construct the electrocatalysts for syngas production. The corresponding hierarchical Co x Ni 1– x –N–C DSAC with coexisting isolated CoN 4 and NiN 4 moieties was constructed by a two-step pyrolysis based on the mesostructured basic magnesium carbonate (m-MgCO 3 ·Mg­(OH) 2 ) templating method .…”