Core-shell structured Ni12P5/Ni3(PO4)2 hollow spheres as difunctional and efficient electrocatalysts for overall water electrolysis

Non-precious metal catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are the cost-effective materials for overall water splitting. Here, we report that the core-shell structured Ni12P5/Ni3(PO4)2 hollow spheres (Ni12P5/Ni3(PO4)2-HS) exhibits high activity and stability towards both HER and OER in strong alkaline media. A current density of 10 mA cm−2 is generated at an overpotential of 0.114 V and 0.318 V in 1 M KOH for HER and OER, respectively. The high activity is attributed to the hollow core-shell (Ni12P5/Ni3(PO4)2) structure that the material adopts under catalytic conditions. The Ni12P5/Ni3(PO4)2-HS can serve as both cathode and anode catalysts for a real water electrolysis cell, which generates a current density of 357.6 mA cm−2 at 1.8 V and stable at 300 mA cm−2 for at least 100 h, the potential catalytic degradation mechanism has been systematically studied and discussed.