Cooperative Copper Single‐Atom Catalyst in 2D Carbon Nitride for Enhanced CO₂ Electrolysis to Methane

Abstract

Renewable electricity powered carbon dioxide (CO2) reduction (eCO2R) to high‐value fuels like methane (CH4) holds the potential to close the carbon cycle at meaningful scales. However, this kinetically staggered 8‐electron multistep reduction still suffers from inadequate catalytic efficiency and current density. Atomic Cu‐structures can boost eCO2R‐to‐CH4 selectivity due to enhanced intermediate binding energies (BEs) resulting from favorably shifted d‐band centers. Herein, we exploit two‐dimensional carbon nitride (CN) matrices, viz. Na‐polyheptazine (PHI) and Li‐polytriazine imides (PTI), to host Cu‐N2 type single atom sites with high density (∼1.5 at%), via a facile metal ion exchange process. Optimized Cu loading in nanocrystalline Cu‐PTI maximizes eCO2R‐to‐CH4 performance with Faradaic efficiency (FECH4) of ≈68% and a high partial current density of 348 mA cm−2 at a low potential of ‐0.84 V versus RHE, surpassing the state‐of‐the‐art catalysts. Multi‐Cu substituted N‐appended nanopores in the CN frameworks yield thermodynamically stable quasi‐dual/triple sites with large interatomic distances dictated by the pore dimensions. First‐principles calculations elucidate the relative Cu‐CN cooperative effects between the two matrices and how the Cu‐Cu distance and local environment dictate the adsorbate BEs, density of states, and CO2‐to‐CH4 energy profile landscape. The 9N pores in Cu‐PTI yield cooperative Cu‐Cu sites that synergistically enhance the kinetics of the rate‐limiting steps in the eCO2R‐to‐CH4 pathway.This article is protected by copyright. All rights reserved

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

“…For the FAP-Cu-1.2 catalyst, a CH 4 partial current density of 407.4 mA cm −2 is obtained at a total current density of 600 mA cm −2 , while the FAP-Cu-0.6 catalyst can also exhibit a maximum CH 4 partial Fig. 3 (a-c 29 2 of 7% Au-Cu, 30 3 of Cu/Al 2 O 3 , 31 4 of CuFe-SA, 32 5 of Cu-Ce-O x , 33 6 of Cu-TDPP-NS, 34 7 of Cu clusters/DRC, 35 8 of Cu-DBC, 36 9 of Ag@Cu 2 O, 37 10 of CeO 2 cluster-7% Cu, 38 11 of Cu PTI, 39 12 of carbon coated on Cu/Cu 2 O, 40 13 of 20%Cu/MgSiO 3 41 and 14 of NNU-33(H) 42 ).…”

“…(e) CH 4 FE values with different binders. (f) Comparison of the CH 4 partial current densities and FEs of our optimized FAP-Cu-0.6 catalyst with those of other recently reported electrocatalyst for CO 2 -to-CH 4 conversion (the catalyst references are labelled as 1 of Sputter Cu on PTFE,29 2 of 7% Au-Cu,30 3 of Cu/Al 2 O 3 ,31 4 of CuFe-SA,32 5 of Cu-Ce-O x ,33 6 of Cu-TDPP-NS,34 7 of Cu clusters/DRC,35 8 of Cu-DBC,36 9 of Ag@Cu 2 O,37 10 of CeO 2 cluster-7% Cu,38 11 of Cu PTI,39 12 of carbon coated on Cu/Cu 2 O,40 13 of 20%Cu/MgSiO 341 and 14 of NNU-33(H)42 ).…”

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

“…3a). 35 DFT results demonstrate that the triangular 9 N pore size in poly(triazine imide) could lead to a stronger Cu–N binding energy, improving the stability of the Cu atom and optimizing the energy distribution of the reaction intermediates, thus resulting in higher catalytic activity. As a result, the prepared Cu@poly(triazine imide) electrocatalyst (Cu–PTI) exhibits a maximum FE of 68% and a partial current density of −348 mA cm −2 at −0.84 V vs. RHE.…”

Coordination of copper within a crystalline carbon nitride and its catalytic reduction of CO2

“…45 For example, a recent, related study on the electrocatalytic CO 2 reduction by Cu-coordinated (∼1.5 at%) PTI and PHI materials gave a high selectivity (>60%) for CH 4 within a gas diffusion electrode configuration. 46 Analogously, photoelectrochemical and photocatalytic CO 2 reduction studies on carbon nitride materials coordinated by Cu-catalyst sites at their surfaces have exhibited a high selectivity for either CH 4 or CO. 16,47 Thus, these comparatively lower Cu-loadings yield a different product selectivity. Conversely, the results of the current study demonstrate that a nearmaximal coordination of Cu within both the bulk and surfaces of the PTI structure yields a higher selectivity for formate as the CO 2 R product, consistent with the results of the mechanistic calculations.…”