Fig. 1

The illustration of the water electrolyzer[15]"

Fig. 2

(a) The reaction mechanism of HER[23]; (b) The volcano plot of HER[24]"

Fig. 3

(a) The reaction mechanism of OER[23]；(b) The volcano plot of OER[2]"

Fig. 4

The schmatic diagrams of three typical water-splitting electrolyzers: (a) Alkaline water electrolyzer;(b) Proton exchange membrane water electrolyzers; (c) Alkaline exchange membrane water electrolyzers[28]"

Fig. 5

The comparison of powdery electrode and self-supported electrode[36]: (a) Powdery electrode;(b) Self-supported electrode"

Fig. 6

The diagram of process of hydrogen evolution and oxygen evolution"

Fig. 7

The schematic diagram of frabrication of Co(OH)2 based electrode[38]"

Fig. 8

Schematic diagram of three typical components with two compositions: (a) Supported structure; (b) Heterostructure; (c) Core-shell structure"

Fig. 9

(a) The schematic diagram of fabrication of MoS2/NiCo-LDH; (b)-(c) The HER free energy of the edge of MoS2 and interface of Ni(OH)2/MoS2[43]; (d) Fabrication of Ni(OH)2/MoS2[45]; (e) Fabrication of Ni3S2/VO2[46]"

Fig. 10

(a) The low-magnification SEM image of NiFe/Ni/Ni; (b) The high-magnification SEM imageof NiFe/Ni/Ni; (c) OER performance; (d) HER performance[53]"

Fig. 11

Schematic representation of the OER gas delivery path for (a) an alveolus-like polyethylene structure and (b) a flat structure[54]"

Fig. 12

NiFe LDH@NiFe[55] (a) SEM image; (b) OER performance; (c) the comparison of catalytic activity"

Fig. 13

The self-supported electrode based on nanoengineering and correspondinglarge-scale electrode"