Delocalization State-Stabilized Znδ+ Active Sites for Highly Selective and Durable CO2 Electroreduction

Abstract

Zinc (Zn)-based materials are cost-effective and promising single-metal catalysts for CO₂ electroreduction to CO but is still challenged by low selectivity and long-term stability. Undercoordinated Zn (Zn^δ+) sites have been demonstrated to be powerful active centers with appropriate ^*COOH affinity for efficient CO production However, electrochemical reduction conditions generally cause the inevitable reduction of Zn^δ+, resulting in the decline of CO efficiency over prolonged operation. Herein, a Zn cyanamide (ZnNCN) catalyst is constructed for highly selective and durable CO₂ electroreduction, wherein the delocalized Zn d-electrons and resonant structure of cyanamide ligand prevent the self-reduction of ZnNCN and maintain Zn^δ+ sites under cathodic conditions. The mechanism studies based on density functional theory and operando spectroscopies indicate that delocalized Zn^δ+ site can stabilize the key ^*COOH intermediate through hard-soft acid-base theory, therefore thermodynamically promoting CO₂-to-CO conversion. Consequently, ZnNCN delivers a CO Faradaic efficiency (FE) of up to 93.9% and further exhibits a remarkable stability lifespan of 96 h, representing a significant advancement in developing robust Zn-based electrocatalysts. Beyond expanding the variety of CO₂ reduction catalysts, this work also offers insights into understanding the structure-function sensitivity and controlling dynamic active sites.

Keywords: CO2 electroreduction; Zn cyanamide (ZnNCN); delocalization state; long‐term stability; undercoordinated Zn (Znδ+) site.