Biomimetic photoelectrocatalytic conversion of greenhouse gas carbon dioxide: Two-electron reduction for efficient formate production

- A MOFs/semiconductor biomimetic interface was established for PEC CO2 reduction.
- ZIF9 as a “stoma” for CO2 fixation and activation was in-situ grew on Co3O4 NWs.
- CO2 has been PEC reduced to formate with high yield at a low overpotential.
- Rapid electron transfer was achieved by p-p heterojunction between Co3O4 and ZIF9.

Resource utilization of carbon dioxide (CO2) as alternative carbon feedstock is a promising solution to problems of both the energy supply and global warming. Herein, a biomimetic photoelectrocatalytic interface was covalently constructed utilizing cobalt-containing zeolite imidazolate framework (ZIF9) as CO2 fixation and activation substrate, and Co3O4 nanowires (NWs) as the photoelectrocatalyst. Adsorption experiments demonstrated that CO2 could be concentrated on ZIF9 modified Co3O4 NWs. The CO2 surface concentration exhibited a 3.44 fold increment on this hybrid interface than that on Co3O4 NWs. Theoretical calculation elucidated ZIF9 has the capacity for activating CO2 molecule via binding Co atom to the O atom of CO2, resulting in the onset potential of CO2 reduction 284 mV positively shift on ZIF9-Co3O4 NWs than that on Co3O4 NWs. At a low overpotential of 290 mV, CO2 has been photoelectrocatalytically conversion to formate with high conversion rate of 72.3 μmol L−1 cm−2 h−1 and high selectivity of nearly 100% in liquid products. And the heterogeneous electron transfer constant was 2.096 × 10−3 cm s−1. This CO2 conversion process was confirmed to be an instantaneous proton-coupled 2-electron transfer process. This work opens the opportunity for constructing biomimetic photoelectrocatalytic interface with CO2 adsorption, activation and conversion to efficient CO2 resource utilization.

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