Spin-State Engineering in Single-Atom Catalysts for NO x and CO x Electrocatalysis

Abstract

Spin-state engineering has emerged as a powerful strategy for regulating the reactivity of single-atom catalysts (SACs) beyond conventional coordination and electronic structure optimization. In electrocatalytic NOx and COx conversion, many elementary steps involve open-shell intermediates, spin-dependent electron transfer, and radical-like transition states, making catalytic activity and selectivity highly sensitive to the spin configuration of the isolated metal centers. This Perspective introduces a spin-centered framework for SAC electrocatalysis in which spin polarization, spin crossover, and spin-selective orbital interactions govern access to spin-allowed pathways and stabilize key reaction intermediates. We first outline the fundamental spin-chemistry principles relevant to small-molecule activation, including spin selection rules, d-orbital occupation, spin polarization, and spin–orbit coupling. We then discuss how coordination environments, support interactions, adsorbate binding, electrochemical potentials, and external fields can be used to modulate the spin states of SACs under both static and operating conditions. Representative examples in NOx and COx electrocatalysis are highlighted to illustrate how spin-state engineering reshapes adsorption energetics, proton-coupled electron transfer, bond activation, and catalytic selectivity. Finally, we identify emerging opportunities in operando spin characterization, predictive electronic structure theory, and dynamically programmable catalyst design. By integrating spin chemistry with single-atom catalysis, this Perspective establishes the spin state as an active and programmable design parameter for next-generation electrocatalytic transformations.