Fine-tuning asymmetric bimetallic electrocatalysts for selective methanol production

Asymmetric bi-atom catalysts (BACs) provide a versatile platform for tailoring selectivity of the electrochemical CO reduction reaction (CORR). First-principles calculations are conducted to screen fifteen pairwise transition metal combinations (XCu) incorporated into an asymmetric N-coordinated graphene framework (XN2-CuN3). A fundamental structure-property relationship that determines the early stage of CORR is deduced. The d-band center alignment between X and Cu varies and serves as a crucial descriptor for two CO* adsorption: from too strong binding in early TMs, to optimal interactions in late VIIIB-to-IB ones, and to suppression by competitive H* adsorption in Group IIB. For the peak transition, three late VIIIB-based NiCu, PdCu, PtCu, and one IB-based AuCu emerge as promising candidates, enabling efficient 2CO* chemisorption via a donation-backdonation mechanism and lowering the protonation barrier to form the CHO*-based intermediate to below 0.61 eV. Stable X-bound CO* (or CHO*) moderates the intrinsic overactivity of the XN2 moiety while facilitating the reduction of the adjacent CO* partner at the X center towards CH3OH production. This reveals a cooperative dual-site synergy: X dominates overall activity, whereas Cu functions as a transient CO* buffer and electronic mediator. Mechanistic insights that enables refinement of local asymmetry to engineer high-performance site-specific heterogeneous catalysts.