A dual-monodispersed Pt–Ni₃S₂ heterostructure was synthesized through interfacial electronic modulation, resulting in highly active bi-functional electrocatalysts for methanol oxidation and hydrogen evolution. The heterostructure exhibits asymmetrical charge distribution, leading to high-valent Ni sites and negatively charged Pt⁰ sites, which enhance water dissociation and enable the selective conversion of methanol to formate at low potentials (1.45 V) with high efficiency (98%). The catalyst also demonstrates excellent performance in hydrogen evolution, achieving a low overpotential of 61 mV for 10 mA cm⁻² in 1.0 mol L⁻¹ KOH. The catalyst's dual-monodispersed structure and interfacial electronic modulation facilitate the formation of abundant active sites, enhancing both methanol oxidation and hydrogen evolution. The catalyst was tested in a two-electrode system for methanol-water co-electrolysis, achieving a current density of 50 mA cm⁻² at 1.60 V with good reusability. Theoretical studies using DFT confirmed the role of Pt and Ni₃S₂ interactions in modulating the electronic structure, enhancing catalytic activity. The catalyst shows excellent stability and performance in both methanol oxidation and hydrogen evolution, making it a promising candidate for efficient and sustainable electrochemical applications.A dual-monodispersed Pt–Ni₃S₂ heterostructure was synthesized through interfacial electronic modulation, resulting in highly active bi-functional electrocatalysts for methanol oxidation and hydrogen evolution. The heterostructure exhibits asymmetrical charge distribution, leading to high-valent Ni sites and negatively charged Pt⁰ sites, which enhance water dissociation and enable the selective conversion of methanol to formate at low potentials (1.45 V) with high efficiency (98%). The catalyst also demonstrates excellent performance in hydrogen evolution, achieving a low overpotential of 61 mV for 10 mA cm⁻² in 1.0 mol L⁻¹ KOH. The catalyst's dual-monodispersed structure and interfacial electronic modulation facilitate the formation of abundant active sites, enhancing both methanol oxidation and hydrogen evolution. The catalyst was tested in a two-electrode system for methanol-water co-electrolysis, achieving a current density of 50 mA cm⁻² at 1.60 V with good reusability. Theoretical studies using DFT confirmed the role of Pt and Ni₃S₂ interactions in modulating the electronic structure, enhancing catalytic activity. The catalyst shows excellent stability and performance in both methanol oxidation and hydrogen evolution, making it a promising candidate for efficient and sustainable electrochemical applications.