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

Abstract Electrochemically converting CO 2 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 CO 2 electrolysis conditions restricts their practical application. Herein, a sub‐5 nm sized CuInS 2 quantum dots (CIS‐QDs) based electrocatalyst for converting CO 2 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 CO 2 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.