The origin of the elusive preference of copper chalcogenides for selectively converting carbon dioxide (CO2) into formate has long puzzled researchers. Researchers at National Taiwan University have identified a charge-redistribution mechanism that resolves this long-standing debate, providing fundamental insight into the basis of their exceptional selectivity.
For years, copper chalcogenides have intrigued scientists with their unique ability to convert CO2 into formate with remarkable selectivity, an outcome typically associated with p-block metals such as tin or bismuth rather than transition metals. This behavior is particularly striking for copper (Cu), which generally exhibits little intrinsic product selectivity. Despite extensive studies, the origin of this exceptional behavior has remained elusive.
A research team at National Taiwan University has now resolved this long-standing debate. In a recent article published in Nature Communications, the group utilized a suite of operando synchrotron-based X-ray spectroscopic techniques, successfully capturing direct spectroscopic evidence to elucidate the underlying mechanism.
The experimental findings reveal that chalcogenide anions not only stabilize the catalytic structure to prevent over-reduction of cuprous (Cu+) species to metallic Cu⁰, thereby maintaining an electronic configuration favorable for mono-carbon intermediates such as carbon monoxide (CO) and formate, but also induce a charge-redistribution process within these Cu+ sites, which dynamically stabilizes O-bound formate intermediates, steering the CO2 reduction pathway predominantly toward formate formation.
As a result, Cu-chalcogenide catalysts effectively suppress competing CO and multi-carbon pathways, achieving near-complete selectivity for formate. The optimal CuS catalyst delivered an impressive 90% faradaic efficiency for formate at −0.6 V and a formate partial current exceeding an ampere-scale, demonstrating scalability for industrial applications. This work marks an important step toward rational electronic modulation of electrocatalysts and envisions our understanding of how charge redistribution governs selective electrocatalysis.
"Copper chalcogenides have fascinated researchers for decades because of their enhanced formate selectivity, but the true origin of this behavior was never fully understood," said Hao Ming Chen, a distinguished professor of chemistry and co-corresponding author of the study.
"Our study reveals that charge-redistribution dynamics redefine the fundamental principles governing CO2 reduction selectivity and offer a new design strategy for tuning catalyst electronic structure via chalcogen modification."
To see article on Phys.org: https://phys.org/news/2025-12-unraveling-hidden-dynamics-copper-chalcogenides.html