Elucidation of the Synergistic Effect of Dopants and Vacancies on Promoted Selectivity for CO₂ Electroreduction to Formate

Abstract

Sn‐based materials are identified as promising catalysts for the CO2 electroreduction (CO2RR) to formate (HCOO−). However, their insufficient selectivity and activity remain grand challenges. A new type of SnO2 nanosheet with simultaneous N dopants and oxygen vacancies (VO‐rich N‐SnO2 NS) for promoting CO2 conversion to HCOO− is reported. Due to the likely synergistic effect of N dopant and VO, the VO‐rich N‐SnO2 NS exhibits high catalytic selectivity featured by an HCOO− Faradaic efficiency (FE) of 83% at −0.9 V and an FE of > 90% for all C1 products (HCOO− and CO) at a wide potential range from −0.9 to −1.2 V. Low coordination Sn–N moieties are the active sites with optimal electronic and geometric structures regulated by VO and N dopants. Theoretical calculations elucidate that the reaction free energy of HCOO* protonation is decreased on the VO‐rich N‐SnO2 NS, thus enhancing HCOO− selectivity. The weakened H* adsorption energy also inhibits the hydrogen evolution reaction, a dominant side reaction during the CO2RR. Furthermore, using the catalyst as the cathode, a spontaneous Galvanic Zn‐CO2 cell and a solar‐powered electrolysis process successfully demonstrated the efficient HCOO− generation through CO2 conversion and storage.

In Situ Phase Separation into Coupled Interfaces for Promoting CO2 Electroreduction to Formate over a Wide Potential Window

“…Compared with the reported oxidation state Sn‐based catalysts, Cu 2 SnS 3 catalysts exhibit a promising combination of high activity and selectivity for CO 2 to formate over the wide potential windows from −0.6 V to −1.1 V (Figure 2 h). [5b, 6b, 10a, 17] What's more, its current density with and without IR compensation is excellent compared to the reported catalysts in flow cell (Figure S11 and Table S1).…”

Toward computational design of chemical reactions with reaction phase diagram

“…More importantly, our approach can find multiple activity optimums, which is complementary to the Sabatier principle to understand some exceptional experimental observations. For instance, the formic acid production in CO 2 RR over Pd should be via a COOH* pathway, instead of HCOO* pathway, which is able to explain well the exceptional behaviors over Pd 68,69 regarding the CO, H 2 , and formic acid selectivity at varying potentials.…”

A New Strategy for Accelerating Dynamic Proton Transfer of Electrochemical CO2 Reduction at High Current Densities

“…The ZnCO 2 battery ( Figure a) was composed of Zn foil as anode and ZrO 2 @Ni‐NC as cathode, which are immersed in 6.0 m KOH electrolyte containing 0.02 m Zn(CH 3 COO) 2 and 0.5 m KHCO 3 electrolyte, respectively. [ 1b ] Figure 6b displayed the typical charge and discharge voltage profiles, and the onset potential of the discharge process was 0.727 V. During the discharge process, the cathode ZrO 2 @Ni‐NC could maintain a wide CO F.E range of > 90%, and the highest CO F.E. of 94.3% was achieved at 4.0 mA (Figure 6c), demonstrating the superior CO selectivity in the ZnCO 2 battery.…”

“…Electrochemical reduction of CO 2 (CO 2 RR) to value‐added carbonaceous chemicals (such as CO) with renewable energy input has attracted extensive interest. [ 1 ] However, the activation and conversion of stable CO 2 molecules is difficult due to high dissociation energy of CO bonds (750 kJ mol −1 ). [ 2 ] Considerable efforts have been devoted to searching for electrocatalysts based on earth‐abundant elements for such a CO 2 RR process.…”