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• Carbon-supported bimetallic Pd—Cu alloy nanoparticles (NPs) are reported. • Pd 3 Cu/C alloy NPs exhibit excellent activity towards FAO reaction and ORR. • Downshift of Pd d-band center enhances the electrocatalytic activity. • NPs undergo FAO and ORR via dehydrogenation and direct 4e pathways, respectively. Tuning composition of Pd-based bimetallic electrocatalysts of high stability and durability is of great importance in energy-related reactions. This study reports the remarkable electrocatalytic performance of carbon-supported bimetallic Pd–Cu alloy nanoparticles (NPs) towards formic acid oxidation (FAO) and oxygen reduction reaction (ORR). Among various bimetallic compositions, Pd 3 Cu/C alloy NPs exhibits the best FAO and ORR activity. During FAO reaction, Pd 3 Cu/C alloy NPs exhibits a peak with a current density of 28.33 mA cm−2 and a potential of 0.2 V (vs. Ag/AgCl) which is higher than that of the other PdCu compositions and standard 20 wt% Pd/C catalyst. Meanwhile, the onset potential (−0.09 V), half-wave potential (−0.18 V), limiting current density at 1600 rpm (−4.9 mA cm−2) and Tafel slope (64 mV dec−1) values of Pd 3 Cu/C alloy NPs validate its superiority over the conventional 20 wt% Pt/C catalyst for ORR. Experimental and DFT studies have confirmed that the enhanced activity can be attributed to the electronic effect that arises after Cu alloying which causes a downshift of Pd d-band center and structural effect that produces highly dispersed NPs over the carbon matrix with high electrochemically active surface area. [ABSTRACT FROM AUTHOR]