Facile enrichment of sulfur-modified copper nanograin boundaries for efficient CO2 electroreduction and Zn-CO2 battery

Abstract

Generating formic acid/formate (HCOOH/HCOO−) through renewable electricity-powered carbon dioxide reduction reaction (CO2RR) presents an appealing prospect for realizing a carbon-neutral energy cycle. Among various catalysts, sulfur-modified copper (S-Cu) stands out as potential catalysts due to their favorable attributes of high activity and especially earth abundance. However, the development of facile and energy-efficient methods for preparing S-Cu catalysts remains a great challenge. Additionally, there is still a lack of effective strategies to optimize their performance toward CO2RR. Herein, we present a facile and energy-saving method to fabricate a novel S-Cu precursor. After electrochemical activation, the precursor is converted into an S-Cu nanostructured catalyst, featuring a substantial abundance of nanograin boundary sites. This characteristic contributes to an outstanding CO2RR performance toward HCOO−, surpassing most recently reported counterparts. In situ characterizations together with control experiments disclose that the nanograin boundaries of S-Cu catalysts favor the formation of the *OCHO intermediates, while suppressing hydrogen evolution, ultimately boosting HCOO− production. Thus, the enhanced activity stems from the enrichment of nanograin boundary sites which are expected to be a common feature of advanced catalysts to achieve high HCOO− production. Moreover, when the as-prepared S-Cu catalyst is assembled as the cathode in a Zn-CO2 battery, a power density of 1.10 mW cm−2 is achieved, along with an impressive stability exceeding 250 h. This work presents a facile approach for preparing outstanding catalysts and also sheds a new light on optimizing the performance for CO2 electroreduction to HCOO−.