Highly Ethylene‐Selective Electrocatalytic CO₂ Reduction Enabled by Isolated Cu−S Motifs in Metal–Organic Framework Based Precatalysts

Abstract

Copper-based materials are efficient electrocatalysts for the conversion of CO 2 to C 2+ products,a nd most these materials are reconstructed in situ to regenerate active species. It is achallenge to precisely design precatalysts to obtain active sites for the CO 2 reduction reaction (CO 2 RR). Herein, we develop astrategy based on local sulfur doping of aCu-based metal-organic framework precatalyst, in whichthe stable CuÀ Smotif is dispersed in the framework of HKUST-1 (S-HKUST-1). The precatalyst exhibits ahigh ethylene selectivity in an Htype cell with am aximum faradaic efficiency (FE) of 60.0 %, and delivers acurrent density of 400 mA cm À2 with an ethylene FE up to 57.2 %i naflowc ell. Operando X-raya bsorption results demonstrate that Cu d+ species stabilized by the CuÀS motif exist in S-HKUST-1 during CO 2 RR. Density functional theory calculations indicate the partially oxidized Cu d+ at the Cu/Cu x S y interface is favorable for coupling of the *CO intermediate due to the modest distance between coupling sites and optimizedadsorption energy.

Atomic Layer Infiltration Enabled Cu Coordination Environment Construction for Enhanced Electrochemical CO2 Reduction Selectivity: Case Study of a Cu Metal–Organic Framework

“…For HKUST-1 and HKUST-1-nC-Zn samples, the peak wavenumbers of FT-IR at these positions were nearly identical, demonstrating that the MOF framework maintained the versatile integrity of the organic−inorganic hybrid structure after ALI infiltration. 32,51 Additionally, the water-coordinated Cu feature at 1550 cm −1 in HKUST-1 decreased in intensity with the increase of ALI cycles. 52 This phenomenon was consistent with the observed color change of HKUST-1, indicating that the introduction of Zn gradually removed coordinated water molecules and impeded the coordination of other water molecules.…”

“…This could be due to generated Zn−O species occupying the cavity of HKUST-1 and lowering the pore cage, leading to a modest decrease in specific surface area, which also indicated that the successful assembly of the Zn−O clusters with the HKUST-1 framework retained the structural integrity. 32 An ICP-OES analysis was performed in order to quantify the Cu and Zn elements in the HKUST-1 and ALImodified HKUST-1 samples, as shown in Table S2. With an increase in the number of deposition cycles, the content of Zn atoms also increased, and the ratio of Cu to Zn atomic content relatively decreased.…”

“…Theoretical results revealed that S-stable Cu δ+ played a crucial role in the Cu/Cu x S y interface, promoting dimerization of *CO intermediates by optimizing the shape and electrical structure. 32 In spite of the progress, due to the complexity and poor versatility of the traditional calcination and doping control methods, the strategy of the precise and accurate construction of a Cu coordination environment on the reaction pathways of CO 2 RR is still limited. Moreover, the identification of catalytic activity centers and further studies of the reaction mechanism of these systems due to their uneven dispersion of catalytic sites and uncontrollable coordination environment are not well understood.…”

“…Yang et al established a local sulfur-doping strategy using thioacetamide as the sulfur source to disperse steady Cu–S motifs in the skeleton of HKUST-1, and the precatalyst exhibited a high ethylene FE of 60%. Theoretical results revealed that S-stable Cu δ+ played a crucial role in the Cu/Cu x S y interface, promoting dimerization of *CO intermediates by optimizing the shape and electrical structure . In spite of the progress, due to the complexity and poor versatility of the traditional calcination and doping control methods, the strategy of the precise and accurate construction of a Cu coordination environment on the reaction pathways of CO 2 RR is still limited.…”

Utilizing Metal-Organic Frameworks to Achieve High-Efficiency CO2 Electroreduction

“…Wen et al created a technique based on local sulfur doping of a Cu-based MOF pre-catalyst, in which the stable Cu-S motif is spread throughout the HKUST-1 framework (S-HKUST-1) [44]. The precatalyst can be reassembled in situ in the flow cell to provide a Cu(S) matrix with active biphasic copper/copper sulfide interfaces, delivering a current density of 400 mA cm -2 and a high FE of C 2 H 4 (up to 57.2 %).…”