Can N, S Cocoordination Promote Single Atom Catalyst Performance in CO2RR? Fe-N2S2 Porphyrin versus Fe-N4 Porphyrin

Single atom catalysts (SACs) are promising electrocatalysts for CO2 reduction reaction (CO2RR), in which the coordination environment plays a crucial role in intrinsic catalytic activity. Taking the regular Fe porphyrin (Fe-N-4 porphyrin) as a probe, the study reveals that the introduction of opposable S atoms into N coordination (Fe-N2S2 porphyrin) allows for an appropriate electronic structural optimization on active sites. Owing to the additional orbitals around the Fermi level and the abundant Fe dz2 orbital occupation after S substitution, N, S cocoordination can effectively tune SACs and thus facilitating protonation of intermediates during CO2RR. CO2RR mechanisms lead to possible C1 products via two-, six-, and eight-electron pathways are systematically elucidated on Fe-N-4 porphyrin and Fe-N2S2 porphyrin. Fe-N-4 porphyrin yields the most favorable product of HCOOH with a limiting potential of -0.70 V. Fe-N2S2 porphyrin exhibits low limiting potentials of -0.38 and -0.40 V for HCOOH and CH3OH, respectively, surpassing those of most Cu-based catalysts and SACs. Hence, the N, S cocoordination might provide better catalytic environment than regular N coordination for SACs in CO2RR. This work demonstrates Fe-N2S2 porphyrin as a high-performance CO2RR catalyst, and highlights N, S cocoordination regulation as an effective approach to fine tune high atomically dispersed electrocatalysts.

Automated summary

This study demonstrates that N, S coordination may provide a better catalytic environment for single atom catalysts than regular N coordination, making Fe-N2S2 porphyrin a high-performance CO2RR catalyst.