Electrochemical Lithiation Regulates the Active Hydrogen Supply on Ru–Sn Nanowires for Hydrogen Evolution Toward the High-Performing Anion Exchange Membrane Water Electrolyzer

Abstract

Designing a rational electrocatalyst/electrolyte interface with superb active hydrogen supply is of significant importance for the alkaline hydrogen evolution reaction (HER) and anion exchange membrane water electrolyzers (AEMWEs). Here, we propose a strategy to tune the interfacial active hydrogen supply via inducing dissoluble cation into electrocatalysts to boost HER in alkali, with electrochemical lithiated sub-2 nm RuSn_0.8 nanowires (NWs) as a proof of concept. It is found that a part of Li⁺ could dissolve in situ from lithiated RuSn_0.8 NWs during HER, which tends to affect the interfacial structure and facilitate the proton transport. Among all the Li–Ru–Sn and Ru–Sn NWs, the best-performing Li_3.0RuSn_0.8 NWs exhibit the lowest initial overpotential of 66 mV at 100 mA cm^–2 in 1.0 M KOH, which could be further reduced to 38 mV after the 30 000 cycles accelerated stability test (AST). In situ Raman spectroscopy and operando X-ray adsorption spectroscopy indicate that the pristine Li_3.0RuSn_0.8 NWs are highly active toward water dissociation and the dissolved Li⁺ during AST could further enhance the flexibility of the hydrogen bond network for proton transportation. Ab initio molecular dynamics simulations and density functional theory calculations disclose that the incorporation of Li into the Ru–Sn lattice is beneficial to lower the water dissociation barrier, while dissolved Li⁺ at the interface significantly increases the population of interfacial water molecules, thereby providing sufficient active hydrogens for H₂ production. The AEMWE equipped with the Li_3.0RuSn_0.8 NWs cathode delivers an extremely low cell voltage (1.689 V) at an industrial-scale current density (1 A cm^–2) and outstanding stability (56 μV h^–1 loss at 1 A cm^–2 after 1000 h galvanostatic test), representing one of the best alkaline HER electrocatalysts ever reported.