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The development of renewable clean energy is imminent as global warming and environmental pollution become more serious issues today. Hydrogen energy has been widely studied as an ideal green energy source. Among several common hydrogen production methods, hydrogen production by electrolysis of water is considered an efficient, environmentally friendly, and sustainable hydrogen production strategy. Transition metal phosphates have outstanding electrocatalytic conductivity and high catalytic efficiency, thus exhibiting catalytic effects similar to noble metals. To further enhance the catalytic activity of the transition metal phosphates, in this paper, the cauliflower-like Co-W-P-O 4 /NF catalyst based on three-dimensional nickel foam was prepared by the method of element doping. The catalyst exhibited good bifunctional catalytic activity in alkaline solution. The prepared Co-W-P-O 4 /NF has a unique crystalline-amorphous phase structure with abundant active sites at the interface. In addition, W atoms can interact with Co atoms to co-optimise the electronic structure, enabling the Gibbs free energy of hydrogen adsorption (ΔG H*) to be close to 0, which is conducive to improving the performance of water electrolysis. To achieve a current density of 10 mA·cm−2, the Co-W-P-O 4 /NF required overpotentials of 42.1 mV for HER and 348.2 mV for OER in 1 M KOH solution, with the Tafel slopes being 48.0 and 83.6 mV·dec−1, respectively. When Co-W-P-O 4 /NF was used as both cathode and anode for water splitting, the two-electrode electrolyzer could achieve 10 mA·cm−2 with only 1.62 V, along with good stability. [Display omitted] • The cauliflower-like Co-W-P-O 4 /NF with crystalline-amorphous phase structure is prepared. • Co-W-P-O 4 /NF catalyst shows good bifunctional catalytic activity in alkaline solution. • The electron rearrangement and the rough surface structure can improve the performance of catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • Grape cluster Cu-Co-P/NF was prepared by one-step potentiostatic electrodeposition. • Cu-Co-P/NF exhibit excellent catalytic activity and high stability for HER and OER. • The moderate amount of Cu doping could tune the electronic structure. The application of non-precious metal bifunctional electrode materials is relevant to solving the current serious energy and environmental problems. In this study, the Cu-Co-P/NF bifunctional electrocatalyst with grape-like clusters was successfully prepared for water splitting using nickel foam (NF) as a substrate by electrodeposition. In alkaline conditions, the catalysts showed good catalytic activity and stability in both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). At 10 mA cm-2, the overpotential required for HER was only 64 mV, whereas for OER it was 334 mV, with Tafel slopes of 40 mV dec-1 and 74 mVdec-1, respectively, and almost negligible potential fluctuations after 49 h and 52 h of testing under continuous electrolysis. Furthermore, the two-electrode electrolyzer required only 1.55 V to achieve 10 mA cm-2 in 1 M KOH solution when Cu-Co-P/NF was used as both cathode and anode for water splitting, which was superior to most previously reported electrocatalysts, and it also showed good durability in a 82 h test. Therefore, it has promising applications in industrial electrolytic systems. The unusual Cu-Co-P/NF with grape-like clusters, as well as the synergistic effect between Co and Cu atoms and the high electrochemically active surface area (ECSA), are responsible for the remarkable catalytic performance. [ABSTRACT FROM AUTHOR]