Graphene layer encapsulated MoNi4-NiMoO4 for electrocatalytic water splitting

[Display omitted] •Core-shell catalyst of graphene layer coated MoNi4-NiMoO4 is developed.•High intrinsic activity and large ECSA are achieved.•Graphene layer accelerates charge transfer and benefits for durability.•Low overpotentials of 55 and 206 mV at 10 mA cm−2 for HER and OER.•High bifunctionality of 1.44 V at 10 mA cm−2 for overall water splitting. Developing active and cheap bifunctional electrocatalysts is crucial and challenging for overall water splitting. This work reports a core-shell structured catalyst supported on nickel foam, which is composed of hybrid MoNi4 alloy and NiMoO4 encapsulated in graphene shell layer. The core catalyst of MoNi4-NiMoO4 supplies robust intrinsic activity and high conductivity. The graphene shell accelerates the charge transfer and provides additional protection for core catalyst. Hence, the present G@MoNi4-NiMoO4/NF exhibits excellent catalytic properties for alkali water splitting, with low overpotentials of 55 mV and 206 mV at 10 mA cm−2 for HER and OER, respectively. The efficient activity for overall water splitting is further demonstrated by a low cell voltage of 1.44 V at 10 mA cm−2 in the bifunctional G@MoNi4-NiMoO4/NF electrodes assembled electrolyzer, showing great promise for practical application.