High‐Density Rare‐Earth Single‐Atom‐Triggered Unconventional Transition of Adsorption Configuration on La₁Pd Monatomic Alloy Metallene for Sustainable Electrocatalytic Alkynol Semi‐Hydrogenation

Abstract Electrocatalytic alkynol semi‐hydrogenation for the high‐value chemicals alkenol with mild conditions and carbon‐free emission is a potentially green and sustainable alternative to conventional thermocatalytic routes, which generally involves the design of electrocatalysts with high activity and high selectivity. Here, the rare‐earth single‐atom (Ln = La, Nd, Pr) coordinated Pd metallene (Ln₁Pdene) is reported for electrocatalytic 2‐methyl‐3‐butyn‐2‐ol (MBY) semi‐hydrogenation reaction (MBY ESHR) to synthesis of 2‐methyl‐3‐buten‐2‐ol (MBE). Typically, in alkaline medium containing 0.1 m MBY, MBY conversion and MBE selectivity of La₁Pdene are as high as ≈97% and ≈95%, respectively, with excellent electrocatalytic stability. Meanwhile, in situ infrared spectra reveal the conversion of MBY to MBE during the dynamic electrocatalytic process. Theoretical calculations reveal that the interaction between La single‐atom and Pd host triggers an unconventional transformation of the intermediate MBE* adsorption configuration during electrocatalytic hydrogenation, achieving the optimal desorption energy between La₁Pd and target product and optimizing the reaction energy barriers to inhibit the over‐hydrogenation of MBE. Moreover, La single‐atom as the adsorption active site of the hydrogen supplier H₂O effectively reduces the competition adsorption between the reactants MBY and H₂O, rendering La single‐atom and Pd host as the synergistic co‐catalytic active sites to promote the electrocatalytic MBY semi‐hydrogenation reaction.