Manipulating local coordination of copper single atom catalyst enables efficient CO2-to-CH4 conversion

Abstract

Electrochemical CO2 conversion to methane, powered by intermittent renewable electricity, provides an entrancing opportunity to both store renewable electric energy and utilize emitted CO2. Copper-based single atom catalysts are promising candidates to restrain C-C coupling, suggesting feasibility in further protonation of CO* to CHO* for methane production. In theoretical studies herein, we find that introducing boron atoms into the first coordination layer of Cu-N4 motif facilitates the binding of CO* and CHO* intermediates, which favors the generation of methane. Accordingly, we employ a co-doping strategy to fabricate B-doped Cu-Nx atomic configuration (Cu-NxBy), where Cu-N2B2 is resolved to be the dominant site. Compared with Cu-N4 motifs, as-synthesized B-doped Cu-Nx structure exhibits a superior performance towards methane production, showing a peak methane Faradaic efficiency of 73% at −1.46 V vs. RHE and a maximum methane partial current density of −462 mA cm−2 at −1.94 V vs. RHE. Extensional calculations utilizing two-dimensional reaction phase diagram analysis together with barrier calculation help to gain more insights into the reaction mechanism of Cu-N2B2 coordination structure.

Status and challenges for CO2 electroreduction to CH4: advanced catalysts and enhanced strategies

“…33 In principle, the key step in CO 2 electroreduction into CH 4 is the protonation of *CO intermediates to *CHO. The main competing reaction processes are the dimerization of *CO to C 2+ products and the direct desorption of *CO from the catalyst surface to produce gaseous CO. 34 Among them, single-atom Cu electrocatalysts with monodisperse catalytic sites are expected to exhibit a superior performance for CO 2 electroreduction into CH 4 , owing to the inhibited C–C coupling process. However, it is still a great challenge to achieve the controlled fabrication of Cu–SACs with the desired stability.…”

“…With the guidance of theoretical studies revealing that the introduction of boron into the Cu–N 4 motif can enhance the binding of CO* and CHO* intermediates, Zeng and co-workers synthesized B, N-doped Cu–SACs (BNC–Cu) by a co-doping strategy, which delivers a superior performance towards CH 4 production. 34 Compared to pristine Cu–N 4 , the Cu–N x B y configuration can strongly stabilize *COOH and *CHO, leading to a high CH 4 production (Fig. 11a).…”

Insight on Atomically Dispersed Cu Catalysts for Electrochemical CO2 Reduction

“…(c) FT-EXAFS spectra of BNC-Cu at Cu K-edge under different applied potentials. (d) Two-dimensional (quasi) activity and selectivity map for ECO 2 R reaction and HER at −1.46 V. Reprinted with permission under a Creative Commons CC BY License from ref . Copyright 2023 Springer Nature.…”

Pyrolysis-free synthesis of a high-loading single-atom Cu catalyst for efficient electrocatalytic CO2-to-CH4 conversion

“…Isolating Cu active sites as single atom states is an effective approach to inhibit the C–C coupling during the CO 2 RR, thus facilitating multielectron-reduction to CH 4 . 7 Presently, a mainstream method for the synthesis of single-atom catalysts is to calcinate the mixture of metal precursors with C and N sources, in which the single atoms are conventionally anchored on carbon-based substrates coordinated with nitrogen ligands. 8–10 The C and N sources can be small molecular compounds (such as dopamine, 11 pyrrole 12 and o -phenylenediamine 13 ), polymers (such as polyphthalocyanine 14 and polyaniline 15 ) and carbon materials (such as carbon quantum dots, 16 graphene 8,17 and metal–organic frameworks 18,19 ).…”