The
development of bifunctional catalysts possessing high efficiency
and excellent stability was still a challenge as regards overall water
splitting. Herein, a reasonable space division strategy of Ni foam
(NF) was proposed to design a bifunctional catalyst. Ni-P alloy was
loaded on carbon nanotubes (CNTs) through Pd-free electroless plating
(Ni-P/CNTs). Subsequently, the Ni-P/CNT catalysts mixed with melamine
were annealed for N doping. The N-doped CNTs coated with N-doped Ni3P and Ni nanoparticles (N-Ni3P-Ni/N-CNTs) were
obtained. Finally, the N-Ni3P-Ni/N-CNTs were used as a
filler to divide the pore size of NF by electroplating Ni, obtaining
a network-like hierarchical porous electrode (N-Ni3P-Ni/N-CNTs/NF).
This hierarchical porous structure exposed abundant catalytically
active sites, facilitated the mass transfer, and prevented the catalyst
agglomeration and corrosion that promote electrolyte contact and favor
facile electron transfer kinetics. On the basis of the rational design,
a self-supported N-Ni3P-Ni/N-CNTs/NF electrode showed a
high specific surface area and exhibited superior electrocatalytic
performances. The electrode achieved low overpotential of 73 and 270
mV at 10 mA cm–2 for the hydrogen and oxygen evolution
reaction, respectively. Besides, it required a cell voltage of only
1.57 V to achieve 20 mA cm–2 when assembled in a
1 M KOH electrolyte for overall water splitting. Hence, this study
represented a rational design of self-supported bifunctional electrode
for overall water splitting.