Promoting stability of sub-3 nm In₂S₃ nanoparticles via sulfur anchoring for CO₂ electroreduction to formate

The p-block metal (In, Sn, Bi, etc.)-based electrocatalysts have exhibited excellent activity in the electrocatalytic CO₂ reduction (ECR) to formate. However, the rapid decrease in catalytic activity caused by catalyst reconstruction and agglomeration under ECR conditions significantly restricts their practical applications. Herein, we developed a sulfur anchoring strategy to stabilize the high-density sub-3 nm In₂S₃ nanoparticles on sulfur-doped porous carbon substrates (i-In₂S₃/S-C) for formate production. Systematic characterizations evidenced that the as-prepared catalyst exhibited a strong metal sulfide-support interaction (MSSI), which effectively regulated the electronic states of In₂S₃, achieving a high formate Faradaic efficiency of 91% at −0.95 V vs. RHE. More importantly, the sulfur anchoring effectively immobilized the sub-3 nm In₂S₃ nanoparticles to prevent them from agglomeration. It enabled the catalysts to exhibit much higher durability than the In₂S₃ samples without sulfur anchoring, demonstrating that the strong MSSI and fast charge transfer on the catalytic interface could significantly promote the structural stability of In₂S₃ catalysts. These results provide a viable approach for developing efficient and stable electrocatalysts for CO₂ reduction.