High‐Density CuInS2 Quantum Dots for Efficient and Stable CO2 Electroreduction

Electrochemically converting CO₂ back into fuels and chemicals is promising in alleviating the greenhouse effect worldwide. Various high-efficiency catalysts have been achieved, yet the unsatisfied structural stability under CO₂ electrolysis conditions restricts their practical application. Herein, a sub-5 nm sized CuInS₂ quantum dots (CIS-QDs) based electrocatalyst for converting CO₂ into CO are developed. Taking advantage of the stable M─Ch (metal-chalcogenide) covalent bonds, and unique p-block metal properties, the as-prepared catalyst exhibits excellent structural stability under large overpotentials and can achieve a high CO Faradaic efficiency (FE) of 86% (total CO₂ reduction FE of 89%) at -0.65 V versus reversible hydrogen electrode with long-term durability of 40 h and outstanding current densities of 10.6 mA cm^-2 simultaneously. Furthermore, detailed electrochemical analyses revealed that the excellent performance of the as-prepared catalysts shall be attributed to the high-density active sites and fast charge transfer brought by the ultrasmall size of CIS-QDs. This work provides insights into the design of high-density and stable catalytic sites for developing high-performance electrocatalysts.