From single- to dual-atom catalysts: design rules for oxygen evolution electrocatalysts

Dual-Atom Catalysts (DACs) have emerged as a promising new frontier in electrocatalysis, with the potential to surpass their Single-Atom Catalyst (SAC) counterparts through the cooperative interaction of adjacent metal sites. DACs are often presumed to exhibit superior catalytic performance because of their enhanced ability to bind reaction intermediates. However, whether this cooperative effect systematically translates into superior catalytic activity remains an open and debated question. In this work, we conduct a systematic Density Functional Theory (DFT) screening of homonuclear DACs and directly compare their catalytic behavior with that of the corresponding SACs. We focus on the Oxygen Evolution Reaction (OER), a key process in electrochemical energy conversion technologies. Unlike SACs, dual-site intermediates possess significantly greater conformational flexibility, which can disrupt the linear scaling relationships that govern the activity of many heterogeneous catalysts. Our results confirm that DACs generally exhibit stronger adsorption of OER intermediates than their SAC counterparts. However, this enhanced binding proves detrimental for early transition metals, leading to unfavorable reaction energetics. This effect originates from the formation of adducts with oxo character, hindering O2 desorption on early-to-mid transition metals. In contrast, late transition metals provide a more balanced interaction strength and emerge as the most promising candidates for OER catalysis in DAC configurations. Based on these findings, we propose a set of design principles and screening guidelines for dual-atom catalysts, offering practical insights to support the experimental development of next-generation OER materials.