The Cu 3 (THT) 2 catalyst achieves the optimal Faradaic efficiency (FE) towards CH 4 , reaching 63.5% at –1.4 V versus the reversible hydrogen electrode (RHE; all subsequent potentials are referred to RHE and were not iR -corrected), along with an industrial level CH 4 partial current density of –189.6 mA cm – 2 . Additionally, the Cu-S 4 sites in Cu 3 (THT) 2 display good stability and can sustain its initial activity even after continuous electrolysis for 21,000 seconds. In stark contrast, Cu 3 (HITP) 2 , featuring Cu-N 4 sites, exhibits markedly inferior CO 2 RR performance, with a CO Faradaic efficiency (FE CO ) of merely 40%, and a tendency to decompose and reconstruct into Cu 2 O particles after a mere 300 seconds of electrolysis.
Theoretical calculations reveal that S coordination atoms, featuring low electronegativity, can endow Cu-S 4 sites with higher electron density compared to Cu-N 4 site. This leads to a stronger binding with the 5σ/1π-orbital of *CO and a better π-backbonding with 2π*-orbital of *CO. In addition, the divalent S atom in Cu-S 4 motifs serves as an electron acceptor, capable of binding with the O atom in *CO through S∙∙∙O weak interactions, which further optimizes the binding strength of *CO. As a consequence, the combined effect of the elevated electronic density in Cu-S 4 and high oxophilic S atoms is envisioned to break the scaling relationship in CO 2 -to-CH 4 .
To the best of our knowledge, this work is the first attempt to reveal the role of non-metallic S center in CO 2 electrocatalyst for switching the main products from simple CO to high-valued CH 4 with high selectivity and large current density.
Science Bulletin
Experimental study