Gas Diffusion Strategy for Inserting Atomic Iron Sites into Graphitized Carbon Supports for Unusually High‐Efficient CO₂ Electroreduction and High‐Performance Zn–CO₂ Batteries

Abstract

Emerging single‐atom catalysts (SACs) hold great promise for CO2 electroreduction (CO2ER), but the design of highly active and cost‐efficient SACs is still challenging. Herein, a gas diffusion strategy, along with one‐step thermal activation, for fabricating N‐doped porous carbon polyhedrons with trace isolated Fe atoms (Fe1NC) is developed. The optimized Fe1NC/S1‐1000 with atomic Fe‐N3 sites supported by N‐doped graphitic carbons exhibits superior CO2ER performance with the CO Faradaic efficiency up to 96% at −0.5 V, turnover frequency of 2225 h−1, and outstanding stability, outperforming almost all previously reported SACs based on N‐doped carbon supported nonprecious metals. The observed excellent CO2ER performance is attributed to the greatly enhanced accessibility and intrinsic activity of active centers due to the increased electrochemical surface area through size modulation and the redistribution of doped N species by thermal activation. Experimental observations and theoretical calculations reveal that the Fe‐N3 sites possess balanced adsorption energies of *COOH and *CO intermediates, facilitating CO formation. A universal gas diffusion strategy is used to exclusively yield a series of dimension‐controlled carbon‐supported SACs with single Fe atoms while a rechargeable Zn–CO2 battery with Fe1NC/S1‐1000 as cathode is developed to deliver a maximal power density of 0.6 mW cm−2.

Carbon‐Supported Single Metal Site Catalysts for Electrochemical CO2 Reduction to CO and Beyond

“…By controlling the pyrolytic temperature, the NiN 4 , NiN 3 C, and NiN 2 C 2 sites could be fabricated at 600, 800, and 900 °C, respectively. It seems that the relationship between pyrolytic temperature and the N coordination number above is a general tendency, which has also been observed for Fe [44] and Cu [52] based samples. However, some works also reported that higher thermal activation temperature (e.g., 1000 °C) could promote MN 4 sites' synthesis, [53] thus producing more graphitic N in the carbonaceous frameworks, which induces charge redistribution and enhances electron-transport properties.…”

Synthesis Strategies, Catalytic Applications, and Performance Regulation of Single‐Atom Catalysts

“…[ 122 ] Recently, many non‐noble metals (Fe, Co, and Ni) SACs have been developed, they matched well with Au and Ag catalysts in terms of Faradaic efficiency for CO 2 RR. [ 123–128 ] For example, a family of isostructural porphyrinic MTV–MOFs had been fabricated by using TCPP and H 2 TCPP as building units with different metal (i.e., Fe, Co, Ni, Cu). CO was identified as the major product during the process of all four M–N–C model catalysts toward CO 2 RR.…”

Metal‐Free Bifunctional Ordered Mesoporous Carbon for Reversible Zn‐CO2 Batteries

“…fabricated isolated Fe atoms anchored on nitrogen‐doped porous carbon, achieving a high FE CO of 96% and a power density of 0.6 mW cm −2 . [ 19 ] Xie et al. developed a porous Pd nanosheet accompanied with enriched edges, resulting in 81.2% energy efficiency between CO 2 and formic acid reversible conversion.…”

“…OER happened during the charging process, which was accompanied by the deposition of Zn on the anode. [ 1,13,19 ] The discharge and charge polarization curves and the corresponding power density of a single Zn‐CO 2 battery are shown in Figure 3b,c. A maximum power density of 0.71 mW cm –2 can be achieved at a current density of 3.0 mA cm –2 , which is even larger than the Fe single‐atom based ones (Table S3, Supporting Information).…”

“…A maximum power density of 0.71 mW cm –2 can be achieved at a current density of 3.0 mA cm –2 , which is even larger than the Fe single‐atom based ones (Table S3, Supporting Information). [ 19 ] Furthermore, at a discharge current density of 0.5 mA cm –2 , a discharge voltage of 0.48 V was obtained with an energy efficiency of 53.2% and an energy density of 308.64 Wh kg –1 (Table S4, Supporting Information). As the discharge current increases to 1.0 mA cm –2 , the energy efficiency comes to 52.8% and the energy density comes to 257.2 Wh kg –1 , comparable with the noble Ir@Au catalyst (Table S3, Supporting Information).…”