Highly Active and Selective Electrocatalytic CO₂ Conversion Enabled by Core/Shell Ag/(Amorphous-Sn(IV)) Nanostructures with Tunable Shell Thickness

Electrochemical CO₂ reduction (ECR) to highly value-added products is regarded as a promising way to capture and utilize atmospheric CO₂. While the large overpotential and low selectivity largely hinder its practical application, it is highly desirable to design promising catalysts for efficient ECR catalysis. Herein, we have designed a series of core/shell Ag/(Amorphous-Sn­(IV)) (Ag/(A-Sn­(IV))) nanoparticles (NPs) as highly active and selective catalysts for ECR. Precise amorphous shell tuning of Ag/(A-Sn­(IV)) NPs reveals that Ag/(A-Sn­(IV)) NPs exhibit volcano-like activity and selectivity toward ECR as a function of the thickness of amorphous shells. The ultrathin amorphous shell not only effectively suppressed the hydrogen evolution reaction (HER) to increase the ECR activity but also converted the ECR product from CO to HCOOH as the applied voltage increased. As a consequence, the optimized core/shell Ag₇₅/(A-Sn­(IV))₂₅ NPs show outstanding performance with a CO faradaic efficiency (FE) of 88.0% and a partial current density of 7.9 mA/cm² at −0.7 V and a HCOOH FE of 75.1% and a partial current density of 13.4 mA/cm² at −0.9 V. It also exhibited negligible change in current density and FE of the main products after a 12 h reaction. Theoretical calculation further confirmed that the regulation of the shell thickness effectively inhibited the HER and enhanced ECR with a 0.6 nm shell thickness of Ag/(A-Sn­(IV)) NPs exhibiting the best activity.