Bismuth-Based Electrocatalysts for Identical Value-Added Formic Acid Through Coupling CO2 Reduction and Methanol Oxidation.

ABSTRACT

It is an effective way to reduce atmospheric CO2 via electrochemical CO2 reduction reaction (CO2 RR), while the slow oxygen evolution reaction (OER) occurs at the anode with huge energy consumption. Herein, methanol oxidation reaction (MOR) is used to replace OER, coupling CO2 RR to achieve co-production of formate. Through enhancing OCHO* adsorption by oxygen vacancies engineering and synergistic effect by heteroatom doping, Bi/Bi2 O3 and Ni─Bi(OH)3 are synthesized for efficient production of formate via simultaneous CO2 RR and methanol oxidation reaction (MOR), achieving that the coupling of CO2 RR//MOR only required 7.26 kWh gformate -1 power input, much lower than that of CO2 RR//OER (13.67 kWh gformate -1 ). Bi/Bi2 O3 exhibits excellent electrocatalytic CO2 RR performance, achieving FEformate >80% in a wide potential range from -0.7 to -1.2 V (vs RHE). For MOR, Ni─Bi(OH)3 exhibits efficient MOR catalytic performance with the FEformate >98% in the potential range of 1.35-1.6 V (vs RHE). Not only demonstrates the two-electrode systems exceptional stability, working continuously for over 250 h under a cell voltage of 3.0 V, but the cathode and anode can maintain a FE of over 80%. DFT calculation results reveal that the oxygen vacancies of Bi/Bi2 O3 enhance the adsorption of OCHO* intermediate, and Ni─Bi(OH)3 reduce the energy barrier for the rate determining step, leading to high catalytic activity.