High‐Rate CO2 Electrolysis to Formic Acid over a Wide Potential Window: An Electrocatalyst Comprised of Indium Nanoparticles on Chitosan‐Derived Graphene

Abstract Realizing industrial‐scale production of HCOOH from the CO2 reduction reaction (CO2RR) is very important, but the current density as well as the electrochemical potential window are still limited to date. Herein, we achieved this by integration of chemical adsorption and electrocatalytic capabilities for the CO2RR via anchoring In nanoparticles (NPs) on biomass‐derived substrates to create In/X−C (X=N, P, B) bifunctional active centers. The In NPs/chitosan‐derived N‐doped defective graphene (In/N‐dG) catalyst had outstanding performance for the CO2RR with a nearly 100 % Faradaic efficiency (FE) of HCOOH across a wide potential window. Particularly, at 1.2 A ⋅ cm−2 high current density, the FE of HCOOH was as high as 96.0 %, and the reduction potential was as low as −1.17 V vs RHE. When using a membrane electrode assembly (MEA), a pure HCOOH solution could be obtained at the cathode without further separation and purification. The FE of HCOOH was still up to 93.3 % at 0.52 A ⋅ cm−2, and the HCOOH production rate could reach 9.051 mmol ⋅ h−1 ⋅ cm−2. Our results suggested that the defects and multilayer structure in In/N‐dG could not only enhance CO2 chemical adsorption capability, but also trigger the formation of an electron‐rich catalytic environment around In sites to promote the generation of HCOOH.