Hierarchical Porous Prism Arrays Composed of Hybrid Ni-NiO-Carbon as Highly Efficient Electrocatalysts for Overall Water Splitting.

Searching for an economical and efficient water splitting electrocatalyst is still a huge challenge for hydrogen production. This work reports one-step synthesis of hierarchical porous prism arrays (HPPAs) composed of Ni-NiO nanoparticles embedding uniformly in graphite carbon (Ni-NiO/C HPPAs), which is derived from metal-organic framework (CPO-27-Ni) prism arrays grown on nickel foam (NF). Remarkable features of the prism arrays, synergistic effect of Ni-NiO/C, porous graphite carbon, high conductive NF, and good contact between catalyst and current collector result in excellent electrocatalytic performance of Ni-NiO/C HPPAs@NF. Ni-NiO/C HPPAs@NF shows a small overpotential of ∼49.48 mV at the current density of 10 mA cm-2, low Tafel slope of 74 mV dec-1 and robust stability for hydrogen evolution reaction (HER) in alkaline media. Especially, the overpotential for HER of Ni-NiO/C HPPAs@NF is only ∼132 mV at the current density of 185 mA cm-2, almost the same as the value from the Pt/C. Furthermore, for oxygen evolution reaction in basic media, Ni-NiO/C HPPAs@NF shows better catalytic activity, lower Tafel slope and higher durability than precious IrO2. The above finding offers an effective strategy to design the bifunctional electrocatalysts for overall water splitting.