Promoting water dissociation for efficient solar driven CO2 electroreduction via improving hydroxyl adsorption

Abstract

Exploring efficient electrocatalysts with fundamental understanding of the reaction mechanism is imperative in CO2 electroreduction. However, the impact of sluggish water dissociation as proton source and the surface species in reaction are still unclear. Herein, we report a strategy of promoting protonation in CO2 electroreduction by implementing oxygen vacancy engineering on Bi2O2CO3 over which high Faradaic efficiency of formate (above 90%) and large partial current density (162 mA cm−2) are achieved. Systematic study reveals that the production rate of formate is mainly hampered by water dissociation, while the introduction of oxygen vacancy accelerates water dissociation kinetics by strengthening hydroxyl adsorption and reduces the energetic span of CO2 electroreduction. Moreover, CO3* involved in formate formation as the key surface species is clearly identified by electron spin resonance measurements and designed in situ Raman spectroscopy study combined with isotopic labelling. Coupled with photovoltaic device, the solar to formate energy conversion efficiency reaches as high as 13.3%.

A coupled electrocatalytic system with reduced energy input for CO2 reduction and biomass valorization

“…Recent evidence suggests that proton-feeding plays a vital role in eCO 2 RR because the dissociation of H 2 O to generate H + in a neutral/alkaline medium is rather sluggish. [17][18][19][20] Therefore, a rational design of Bi-based catalysts that could facilitate water dissociation to provide sufficient H + for the protonation step would markedly boost the formate production rate. However, Bi itself is inert for water dissociation due to its poor adsorption of H + .…”

Construction of Low‐Coordination Cu−C2 Single‐Atoms Electrocatalyst Facilitating the Efficient Electrochemical CO2 Reduction to Methane

“…To eliminate interference from the solution system, the EPR was firstly conducted in a KHCO 3 solution containing 100 mM DMPO prior to electrochemical testing, and the result displays the presence of characteristic peaks of CO 3 ⋅ radicals in pure KHCO 3 solution without exerting potential (Figure 4b). [16] In contrast, for the pure KHCO 3 solution, 9 characteristic peaks become visible after 5 minutes of electrolysis at a constant potential of −1.1 V with Cu−SAs/HGDY as electrocatalyst. These peaks are consistent with the simulation results and are assigned to DMPO−⋅H (A N =16.5 G, A H =22.5 G) (Figure S17), confirming the formation of H⋅ [16] .…”

“… [16] In contrast, for the pure KHCO 3 solution, 9 characteristic peaks become visible after 5 minutes of electrolysis at a constant potential of −1.1 V with Cu−SAs/HGDY as electrocatalyst. These peaks are consistent with the simulation results and are assigned to DMPO−⋅H (A N =16.5 G, A H =22.5 G) (Figure S17), confirming the formation of H⋅ [16] . Interestingly, a noticeable decrease in the intensity of H⋅ peaks is observed after the introduction of CO 2 , indicating the consumption of H⋅ during the e‐CO 2 RR process (Figure 4b).…”

Construction of Low‐Coordination Cu−C2 Single‐Atoms Electrocatalyst Facilitating the Efficient Electrochemical CO2 Reduction to Methane

“…These peaks are consistent with the simulation results and are assigned to DMPOÀ * H (A N = 16.5 G, A H = 22.5 G) (Figure S17), confirming the formation of H * . [16] Interestingly, a noticeable decrease in the intensity of H * peaks is observed after the introduction of CO 2 , indicating the consumption of H * during the e-CO 2 RR process (Figure 4b). Moreover, to further testify the generation of H * during the electrolysis, EPR testing was also conducted under the same conditions in a neutral system using a 0.5 M Na 2 SO 4 solution as electrolyte to eliminate the potential interference of alkaline conditions.…”