All roads lead to Rome: An energy-saving integrated electrocatalytic CO2 reduction system for concurrent value-added formate production

Abstract

Electrochemical CO2 reduction (CO2R) to value-added fuels has been actively pursued to reduce the carbon intensity of our energy and products-driven economy. Conventional CO2R is always coupled with the anodic oxygen evolution reaction (OER), resulting in high electricity input being consumed by the OER due to its large energy barrier and sluggish kinetics. Herein, OER is replaced with selective methanol oxidation reaction (MOR) on non-noble electrocatalysts. In an integrated cell, CO2R is conducted on the cathode of Bi nanoparticles and MOR is performed on the anode of Ni(OH)2 in alkaline electrolyte. Over 92% selectivity for cathodic reduction of CO2 into formate and 100% selectivity for anodic oxidation of methanol to formate are achieved at high current densities within a wide potential range. The use of the integrated system significantly lowers the specific energy consumption by 57.3% reduction for individual CO2R and 71.2% reduction for individual MOR for 1 mol formate generation. This novel strategy for concurrent formate generation at the cathode and anode dramatically increases the valuable fuels production with low electricity consumption. This study thus highlights the promise that coupling CO2R with viable alternative oxidation reaction is theoretically and technically feasible and presents significant economic benefits.