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

Abstract

Single atom catalysts (SACs) are promising electrocatalysts for CO₂ reduction reaction (CO₂ RR), in which the coordination environment plays a crucial role in intrinsic catalytic activity. Taking the regular Fe porphyrin (Fe-N₄ porphyrin) as a probe, the study reveals that the introduction of opposable S atoms into N coordination (Fe-N₂ S₂ porphyrin) allows for an appropriate electronic structural optimization on active sites. Owing to the additional orbitals around the Fermi level and the abundant Fe <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>d</mml:mi><mml:msup><mml:mi>z</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:msub></mml:mrow></mml:math> orbital occupation after S substitution, N, S cocoordination can effectively tune SACs and thus facilitating protonation of intermediates during CO₂ RR. CO₂ RR mechanisms lead to possible C1 products via two-, six-, and eight-electron pathways are systematically elucidated on Fe-N₄ porphyrin and Fe-N₂ S₂ porphyrin. Fe-N₄ porphyrin yields the most favorable product of HCOOH with a limiting potential of -0.70 V. Fe-N₂ S₂ porphyrin exhibits low limiting potentials of -0.38 and -0.40 V for HCOOH and CH₃ OH, 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 CO₂ RR. This work demonstrates Fe-N₂ S₂ porphyrin as a high-performance CO₂ RR catalyst, and highlights N, S cocoordination regulation as an effective approach to fine tune high atomically dispersed electrocatalysts.