Selective suppression of water oxidation toward preferential small-molecule oxidation on Mn–NiAl layered double hydroxides for low-voltage hydrogen generation

Abstract

Selective anodic electrocatalysts that promote small-molecule nucleophilic oxidation reactions (NORs) in place of the sluggish oxygen evolution reaction (OER) are essential for energy-efficient hydrogen production. Herein, a series of Mn-incorporated NiAl layered double hydroxides (Mn_xNi_1−xAl-LDHs) with systematically tuned Mn-to-Ni ratios were synthesized via a coprecipitation method and evaluated as anodic electrocatalysts for NORs in alkaline media. Structural and spectroscopic analyses confirm the successful incorporation of Mn into the NiAl-LDH lattice without detectable secondary phases. Electrochemical studies reveal that Mn incorporation regulates redox accessibility and surface hydroxide interactions, enabling preferential small-molecule oxidation over OER, supported by consistent from electrochemical behavior. At 100 mA cm⁻², the optimized Mn_10.0–NiAl-LDH requires 1.607 V for OER, whereas NORs proceed at significantly lower anodic potentials (1.588–0.042 V), depending on the substrate, demonstrating a substantial reduction in anodic energy input compared to conventional OER. Importantly, this work establishes a kinetic regulation strategy that selectively suppresses OER while activating NOR pathways within a single LDH platform. This behavior is attributed to Mn-induced electronic structure modulation and enhanced interfacial charge-transfer kinetics, as inferred from consistent spectroscopic and electrochemical correlations rather than a quantitatively derived kinetic model. Overall, a clear composition–activity–selectivity relationship is established, providing a rational design framework for selective transition-metal electrocatalysts toward low-voltage hydrogen generation.