Near‐ and Long‐Range Electronic Modulation of Single Metal Sites to Boost CO₂ Electrocatalytic Reduction

Abstract

Tuning the electronic structure of the active center is effective to improve the intrinsic activity of single‐atom catalysts but the realization of precise regulation remains challenging. Herein, a strategy of “synergistically near‐ and long‐range regulation” is reported to effectively modulate the electronic structure of single‐atom sites. ZnN4 sites decorated with axial sulfur ligand in the first coordination and surrounded phosphorus atoms in the carbon matrix are successfully constructed in the hollow carbon supports (ZnN4S1/P‐HC). ZnN4S1/P‐HC exhibits excellent performance for CO2 reduction reaction (CO2RR) with a Faraday efficiency of CO close to 100%. The coupling of the CO2RR with thermodynamically favorable hydrazine oxidation reaction to replace oxygen evolution reaction in a two‐electrode electrolyzer can greatly lower the cell voltage by 0.92 V at a current density of 5 mA cm−2, theoretically saving 46% of energy consumption. Theoretical calculation reveals that the near‐range regulation with axial thiophene‐S ligand and long‐range regulation with neighboring P atoms can synergistically lead to the increase of electron localization around the Zn sites, which strengthens the adsorption of *COOH intermediate and therefore boosts the CO2RR.

Remote p–d orbital hybridization via first/second-layer coordination of Fe single atoms with heteroatoms for enhanced electrochemical CO2-to-CO reduction

“…34 On the other hand, strong adsorption of the M site toward the *COOH intermediate is required for the succeeding hydrogenative step to exclusively afford *CO. To balance *CO desorption and *COOH adsorption for enhanced CO 2 -to-CO electroreduction, the doping of p-block elements into the d-block M center in the second coordination layer is envisioned to induce remote p–d orbital hybridization, which can transmit the electrons from the p-block elements to the d-block M center, and modulate the electronic structure M–N 4 site in a very small range. 26,35,36…”

High-coordination Fe–N4SP single-atom catalysts via the multi-shell synergistic effect for the enhanced oxygen reduction reaction of rechargeable Zn–air battery cathodes

“…33 However, such long-range electron modulation may be limited by the strength of absorbing/donor moieties and the spatial interaction distance, leading to a diminished effect of electron delocalization. 34,35 Hence, efficient modulation of the first CS has been proposed and extensively studied. 36–40 For instance, ligand atoms have been directly anchored to host atoms, aimed at modulating the microenvironment or the electronic spin state of metal active centers for tailored d-band centers and intrinsic activity of Fe–N–C catalysts.…”

Carbonyl-linked cobalt polyphthalocyanines as high-selectivity catalyst for electrochemical CO2 reduction

“…1 As one of the promising strategies against increased CO 2 emissions, the electrocatalytic CO 2 reduction can take full advantage of renewable energy, and value-added products (carbon monoxide, formic acid, methanol, methane, and so on) can be obtained. 2,3 Up to now, several materials including metallic catalysts, single-atom catalysts, and molecular catalysts have shown potential catalytic performance for ECR. 4–6 Although diverse reaction pathways are proposed for different electrocatalysts, the commonalities of these pathways are that electrons and protons are needed to participate together during the ECR processes.…”