Exploration of catalysts is the primary focus of the electrochemical nitrogen reduction reaction (NRR). However, cost-effective materials are rarely reported. Herein, we report a composite consisting of a three-dimensional nanoporous CuO structure decorated with PdAgCu alloy nanoparticles (abbreviated as PdAgCu/CuO composites) as a highly effective catalyst. Compared with the nanoporous PdAgCu alloy and PdCu/CuO and Cu/CuO composites, PdAgCu/CuO composites exhibit much superior NRR catalytic activity with a high NH3 production rate of 40.4 mu g h(-1) mg(cat)(-1). In addition, PdAgCu/CuO composites show good catalytic stability for NRR. The superior NRR performance of PdAgCu/CuO composites can be ascribed to the synergistic effects of metals and metal oxides, which are highly significant for the exploration of efficient catalysts for NRR.