Boosting thermo-photocatalytic CO2 conversion activity by using photosynthesis-inspired electron-proton-transfer mediators

Yingxuan Li,Danping Hui,Chuanyi Wang,Yuqing Sun,Ying Wang,Jincai Zhao,Zhijian Wu

doi:10.1038/s41467-020-20444-1

Abstract

Natural photosynthesis proceeded by sequential water splitting and CO2 reduction reactions is an efficient strategy for CO2 conversion. Here, mimicking photosynthesis to boost CO2-to-CO conversion is achieved by using plasmonic Bi as an electron-proton-transfer mediator. Electroreduction of H2O with a Bi electrode simultaneously produces O2 and hydrogen-stored Bi (Bi-Hx). The obtained Bi-Hx is subsequently used to generate electron-proton pairs under light irradiation to reduce CO2 to CO; meanwhile, Bi-Hx recovers to Bi, completing the catalytic cycle. This two-step strategy avoids O2 separation and enables a CO production efficiency of 283.8 μmol g−1 h−1 without sacrificial reagents and cocatalysts, which is 9 times that on pristine Bi in H2 gas. Theoretical/experimental studies confirm that such excellent activity is attributed to the formed Bi-Hx intermediate that improves charge separation and reduces reaction barriers in CO2 reduction.

Highlights

Natural photosynthesis proceeded by sequential water splitting and CO2 reduction reactions is an efficient strategy for CO2 conversion
During the following anodic polarization of Bi/nickel foam (NF), two current peaks can be observed at ca. 0.45 and 0.62 V, which are ascribed to hydrogen desorption (Hdes) and hydrogen oxidation (Hoxi) on the Bi electrode, respectively[20]
Such behavior is not observed in the Cyclic voltammetry (CV) curve of NF in Fig. 2b, indicating that the presence of Bi is responsible for the electrochemical hydrogen storage behavior of Bi/NF

Summary

Introduction

Natural photosynthesis proceeded by sequential water splitting and CO2 reduction reactions is an efficient strategy for CO2 conversion. The obtained Bi-Hx is subsequently used to generate electron-proton pairs under light irradiation to reduce CO2 to CO; Bi-Hx recovers to Bi, completing the catalytic cycle. This two-step strategy avoids O2 separation and enables a CO production efficiency of 283.8 μmol g−1 h−1 without sacrificial reagents and cocatalysts, which is 9 times that on pristine Bi in H2 gas. After the rate-determining step, the intermediate CO2− is subsequently reduced via the protonassisted electron transfer approach, in which H2 or H2O is utilized as the proton source[1,2,3] In these CO2 reduction processes, the types of the products are determined by the number of the transferred proton–electron pairs (Eqs. 2–5)[2]: CO2 þ eÀ 1⁄4 CO2À; ð1Þ. Natural photosynthesis provides a two-step reaction model for innovative catalyst design in CO2 conversion with H2O

Methods

Results

Conclusion