Selective Hydrogen Evolution Reaction in HMF-Containing Mild-Alkaline Electrolytes on Structurally Engineered...

The replacement of the oxygen evolution reaction (OER) with biomass-derived molecule oxidation offers a promising strategy to reduce the energy demand of alkaline water electrolysis while allowing the simultaneous production of value-added chemicals. However, the practical implementation of such coupled systems remains limited by the scarcity of cathode materials that are selective toward the hydrogen evolution reaction (HER) in the presence of reactive organic substrates. In this work, we present the synthesis and electrocatalytic performance of a noble-metal-free and scalable MoS₂ nanosheet@graphene nanoplatelet (MoS₂ Nsh@GNP) composite designed for effective hydrogen production in mild-alkaline media in the presence of hydroxymethylfurfural (HMF) as a biomass-derived organic building block molecule. The hexagonal 2H-MoS₂ nanosheet morphology with maximized accessible catalytic edge sites, combined with the enhanced dispersion and 3D-conductivity provided by graphene scaffold, results in a notable improvement of charge transport, as demonstrated by the observed overpotentials of -0.32 V at 10 mA cm^-2 and -0.49 V at 100 mA cm^-2 in 0.1 M NaOH + 1 M Na₂SO₄ (pH ∼13). Systematic electrochemical experiments, coupled with microgas chromatography and ¹H NMR byproduct analyses, reveal that the HER selectivity is preserved up to 30 mM HMF in the electrolyte. Importantly, stable operation at pH 13, intentionally selected to avoid HMF instability at pH 14, demonstrates the suitability of this cathode material for membraneless biomass-assisted alkaline electrolysis.