Breaking the Linear Scaling Relationship by Alloying Micro Sn to a Cu Surface toward CO₂ Electrochemical Reduction

The electrochemical CO₂ reduction reaction (CO₂RR) to HCOOH provides an avenue for reducing global accelerated CO₂ emissions and producing high-value-added chemicals. Nevertheless, the presence of an inherent linear scaling relationship (LSR) between *OCHO and *HCOOH leads to the electrosynthesis of HCOOH being achieved at high cathodic potentials. In this work, by adjusting the different Cu:Sn ratio of Sn_<i>x</i>Cu_(1-<i>x</i>) alloys, we comprehensively explored the electrocatalytic 2e^- CO₂RR performance toward the production of HCOOH. Combining density functional theory calculations with the constant-potential implicit solvent model, the Sn_0.03Cu_0.97 surface alloy was posited to be a promising electrocatalyst with superior HCOOH selectivity and an ultralow limiting potential of -0.20 V in an environment of pH = 7.2. The high performance was found to originate from the breaking of the LSR, which is a result of an extraordinary electronic property of the active Cu site. This work not only advances a global-searched strategy for the rational design of efficient catalysts toward HCOOH production but also provides in-depth insights into the underlying mechanism for the enhanced performance of microalloy electrocatalysts.