Indium Cyanamide for Industrial-Grade CO2 Electroreduction to Formic Acid

Developing industrial-grade electroreduction of CO2 to produce formate (HCOO–)/formic acid (HCOOH) depends on highly active electrocatalysts. However, structural changes due to the inevitable self-reduction of catalysts result in severe long-term stability issues at industrial-grade current density. Herein, linear cyanamide anion ([NCN]2–)-constructed indium cyanamide nanoparticles (InNCN) were investigated for CO2 reduction to HCOO– with a Faradaic efficiency of up to 96% under a partial current density (jformate) of 250 mA cm–2. Bulk electrolysis at a jformate of 400 mA cm–2 requires only −0.72 VRHE applied potential with iR correction. It also achieves continuous production of pure HCOOH at ∼125 mA cm–2 for 160 h. The excellent activity and stability of InNCN are attributed to its unique structural features, including strongly σ-donating [NCN]2– ligands, the potential structural transformation of [N═C═N]2– and [N≡C–N]2–, and the open framework structure. This study affirms metal cyanamides as promising novel materials for electrocatalytic CO2 reduction, broadening the variety of CO2 reduction catalysts and the understanding of structure–activity relationships.