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 (j_formate) of 250 mA cm^-2. Bulk electrolysis at a j_formate of 400 mA cm^-2 requires only -0.72 V_RHE 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.