High cost and restricted activity of electrocatalysis are the major challenges for hydrogen generation and biosensors.In this work,we provided a one-pot synthesis of Cu_(x)Pd_(y)alloy nanoparticles(NPs)with controllable atomic ratio and“clean surface”.Benefiting from the preferable d-band structure,the Cu_(62)Pd_(38)NPs exhibited a lower overpotentials in the hydrogen evolution reaction(HER)over the full pH range.In the acidic media,Cu_(62)Pd_(38)NPs achieved a low overpotential of 28.12 mV for HER,which was 25.73%of Pd NPs.In the neutral solution,the overpotential by Cu_(62)Pd_(38)NPs is only 41.71%for that by uncleaned CuPd NPs.In alkaline media,the overpotential by Cu_(62)Pd_(38)NPs was declined from 38.01 to 20.20 mV after 720 min yielding hydrogen,which was only 53.14%for the initial overpotential.As applied in biosensor,the synergistic effect of Cu and Pd accelerated the kinetics of electrocatalytic process,resulting in an enhanced performance.The glucose sensor constructed by Cu_(67)Pd_(33)exhibited a wider detection range up to 100.0 mM.And the sensitivity is 379.4μA/(mM·cm^(2)),which is ca.4.63 and 14.09 folds for that by pure Cu NPs and Pd NPs,respectively.An optimal atomic percent would be conducive to optimize electrocatalytic activity of Cu_(x)Pd_(y)alloy.The volcano plots for Cu_(x)Pd_(y)would open up a new avenue for designing electrocatalysis with rationalized cost and optimized performance.