C₂N-graphene supported single-atom catalysts for CO₂ electrochemical reduction reaction: mechanistic insight and catalyst screening

Abstract

Single-atom catalysts (SACs) have emerged as an excellent platform for enhancing catalytic performance. Inspired by the recent experimental synthesis of nitrogenated holey 2D graphene (C2N-h2D) (Mahmood et al., Nat. Commun., 2015, 6, 6486-6493), we report density functional theory calculations combined with computational hydrogen electrode model to show that C2N-h2D supported metal single atoms (M@C2N) are promising electrocatalysts for CO2 reduction reaction (CO2 RR). M confined at pyridinic N6 cavity promotes activation of inert O[double bond, length as m-dash]C[double bond, length as m-dash]O bonds and subsequent protonation steps, with *COOH → *CO → CHO predicted to be the primary pathway for producing methanol and methane. It is found that *CO + H+ + e- → *CHO is most likely to be the potential determining step; breaking the scaling relation of *CO and *CHO binding on M@C2N SACs may simply be a rare event that is sensitively controlled by the detailed geometry of the adsorbate. Among twelve metals screened, M@C2N SACs where M = Ti, Mn, Fe, Co, Ni, Ru were identified to be effective in catalyzing CO2 RR with lowered overpotentials (0.58 V-0.80 V).

Recent Progress in Electrocatalytic Methanation of CO2 at Ambient Conditions

“…The authors found that Ti@C 2 N and Mn@C 2 N can catalyze the electrochemical conversion of CO 2 into CH 4 , while, Ru@C 2 N, Fe@C 2 N, Co@C 2 N, Rh@C 2 N preferentially catalyze the CH 3 OH formation. [ 161 ] However, Ju et al. theoretically and experimentally proved that among various M‐N‐C (M = Mn, Fe, Co, Ni, Cu) catalysts, only Fe‐N‐C and Mn‐N‐C catalysts can catalyze the reduction of CO 2 to CH 4 formation.…”

“…[ 150 ] For the prevailing Cu catalyst, both He and Cui demonstrated that atomic Cu catalyst is favor for CH 3 OH generation. [ 158,161 ] However, Ju et al. proposed that Cu‐N‐C catalysts are efficient for CO synthesis due to its all‐downhill energetics for *CO detaching.…”

“…Reproduced with permission. [ 161 ] Copyright 2018, Royal Society of Chemistry. h) Electrochemical CO 2 RR of the Cu–N–C‐800 catalyst.…”

“…© 2021 Wiley-VCH GmbH formation. [161] However, Ju et al theoretically and experimentally proved that among various M-N-C (M = Mn, Fe, Co, Ni, Cu) catalysts, only Fe-N-C and Mn-N-C catalysts can catalyze the reduction of CO 2 to CH 4 formation. [159] Based on operando EXAFS measurements, Leonard and co-workers found a change in the Fe oxidation state accompanied with associated coordination from Fe 2+ to Fe 1+ , which is in agreement with the onset for CH 4 formation around −0.9 V versus RHE, indicating the capacity of coordinative Fe 1+ -N x moiety in catalyzing the conversion of CO 2 into CH 4 .…”

Borophene: A Metal‐free and Metallic Electrocatalyst for Efficient Converting CO2 into CH4

“…[13] Previous studies have proved that nano-sized electrodes have better catalytic performance for ECRs than traditional bulk materials. [14] With the rapid development of nanotechnology, numerous nanomaterials from zero dimensional (0D) to three dimensional (3D), such as copper, [14,15] silver, [16] gold, [17] palladium nanostructures, [18] and metal/nonmetal doped nanomaterials, [19][20][21] have been successfully used as electrodes for ECR. Most of these studies are mainly focused on metalbased electrocatalysts.…”