Controlling emissions of carbon dioxide (CO2) is one of the biggest challenges facing humanity in the 21st century. Electrochemical reduction has become an emerging method for converting of CO2 into useful fuels. Constructing heterojunctions and designing advanced structures to mimic natural photosynthesis is an effective route to convert CO2 into high-energy chemicals with high efficiency and selectivity. Compared to the single-component catalyst, the two components with different function will corporately facilitate the formation of C2 products. In this talk, we will present two examples on tuning the individual compenent to achieven effeicient catalyst for CO2 reduction. The first is about an embedded heterogeneous Sn-Cu bimetallic catalyst allowing highly efficient electrochemical reduction of CO2 to formate with a high faradaic efficiency of 92% at -0.95 V (vs. RHE). In-situ Raman spectroscopy characterisic identifies CO2− and HCOO as the reaction intermediates during electrochemical reduction of CO2 to formate onto the efficient heterogeneous bimetallic catalyst. Moreover, density functional theory calculation reveals that the embedded heterogeneous bimetallic catalyst possesses a strong adsorption of *H and *CO, thus inhibiting formation of H2 and CO and thereby promoting formation of formate. Further investigation points out the conclusion of the atomic Cu acting as a bridge for electron and ion transfer. The second is a type-II heterojunction based on graphitic carbon nitride (g-C3N4)/ZnTe constructed for photoelectrochemical CO2 reduction, yielding an impressive ethanol generation rate of 17.1 µmol cm-2 h-1 at -1.1 V vs. Ag/AgCl. The heterojunction accelerates the separation of the photo-generated electron-hole pairs and the transfer of the electrons from ZnTe to g-C3N4 driving by the interfacial internal electric field (IEF) formed between the two semiconductors. Moreover, ZnTe with high CO2 adsorption capacity serves as CO-producing site, and g-C3N4 with abundant pyridinic N subsequently accomplishes C-C coupling process via adsorbing CO and proton-coupled electron transfer. A pipelined mechanism to rationalize the selective reduction of CO2 to ethanol is proposed and discussed. The study aims at exploring new functional materials to mimic natural photosynthesis.

Heterogeneous catalysts for highly efficient electrochemical reduction of CO2

2019 Fall National Meeting

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