Electrochemical reactions are important method for reducing the carbon footprint of large-scale chemical processes. Highly selective conversion of 5-hydroxymethylfurfural (HMF) to 2,5-dihydroxymethylfuran (DHMF) is achieved under mild conditions through electrocatalytic hydrogenation (ECH) over AgCu nanoalloys supported by the pyrolyzed biomass alginic acid sodium (PA), with the advantage of utilizing the active hydrogen intermediates in the process. The Ag₁Cu₁/PA exhibits outstanding performance in ECH of HMF with a selectivity of 94% toward DHMF at a conversion of 93.2% and the Faraday efficiency (FE) of 61.8%, which are significantly superior to those over Ag/PA (selectivity of 53.89%, conversion of 90.6%, and FE 25.79%). The incorporation of Cu into Ag nanoparticles boosts the charge transferability and lowers the onset potential of ECH. Density functional theory calculations reveal that AgCu alloy provides more electron transfer to HMF and lowers the energy barrier for HMF hydrogenation.