Synthesis Of Ni-based Nano Hydroxide Composite Electrode Materials And Study On Their Electrocatalytic Performance

The global energy and environmental crisis have accelerated the development of sustainable green energy sources,and hydrogen is considered to be the most promising alternative to fossil energy.Among many emerging hydrogen production technologies,electrocatalytic water splitting is believed an efficient and potential method which consists of two half-reactions,the hydrogen evolution reaction?HER?in the cathode and the oxygen evolution reaction?OER?in the anode.It requires a large voltage to drive electrocatalytic water splitting,the practical voltage is range from 1.8 to 2.0 V,which is much higher than the theoretical value of 1.23 V.At present,noble metals?Pt?and noble metal oxides?Ru/Ir oxides?are regarded as the optimal catalysts for HER and OER,respectively,but the practical application is hampered by their scarce resource reserves,high production costs,and insufficient bifunctional activity.Therefore,it is of great significance to develop bifunctional catalysts for HER and OER with high efficiency and low cost.In view of this,three high-performance nickel-based hydroxide composite catalysts are designed and prepared in this paper.The main contents are as follows:?1?Preparation of an anodized nickel foam?NF-A?supported Pt/Ni?OH?₂ nano composite HER electrode?Pt/Ni?OH?₂/NF-A?.Anodizing technology was used to modify the surface of NF to form a porous Ni F₂ network structure with an average pore size of 120nm,and then highly dispersed Pt nanodots/Ni?OH?₂ composites were generated in situ by hydrothermal reaction,the particle size of Pt nanodots is about 3 nm,and its content is only0.229 mg cm^-2_geo.Compared with NF,NF-A,Pt/NF and commercial Pt/C electrodes,the prepared electrode shows good HER performance,it is only required 25.9 m V and 211 m V to deliver current densities of 10 m A cm^-2 and 100 m A cm^-2,respectively,and a low tafel slope of 37.6 m V dec in alkaline media.Pt/Ni?OH?₂/NF-A electrode shows good stability,only 0.33 wt%and 0.61 wt%of Pt loss after 2000 CV cycles and 24h of chronoamperometric test.?2?Preparation of a three-dimensional reduced graphene oxide?3D-r GO?embedded in NF supported Ni Fe nanolayered double hydroxides?Ni Fe-LDHs?OER electrode?Ni Fe-LDHs/NF@3D-r GO?.The graphene oxide?GO?sol was coated on the NF by doctor blade technology to form a GO-embedded NF matrix?NF@GO?,and then freeze-dried at low temperature to transform the graphene oxide into a three-dimensional network structure,forming NF@3D-GO substrate.Ni Fe-LDHs nanosheets were grown in situ by hydrothermal method,meanwhile 3D-GO was simultaneously reduced,the formed Ni Fe-LDHs nanosheets display a high dispersibility and a hexagonal crystal phase.Compared with NF?NF@3D-r GO?Ni Fe-LDHs/NF?Ni Fe-LDHs/NF-r GO and commercial Ir/C electrodes,Ni Fe-LDHs/NF@3D-r GO electrode prepared under optimized conditions displays better OER performance.A low overpotential of 170 m V is needed to deliver a current density of 20 m A cm^-2 in alkaline media.The prepared electrode exhibits good OER stability,and the overpotential increased only about 20 m V after the 24 h stability test.?3?In-situ growth of Pt atom modified Ni Co-LDHs nanowire bifunctional overall water splitting electrode?Pt/Ni Co-LDHs/NF@3D-r GO?on the NF@3D-r GO substrate.Pt was highly dispersed on the prepared electrode with only 0.06%low loading,and it may exist as a single atom.Ni Co-LDHs nanowires were tightly bound to 3D-r GO.Compared with the Ir/C/NF?Ni Co-LDHs/NF and Pt/Ni Co-LDHs/NF electrodes,Ir/C/NF?Ni Co-LDHs/NF?Pt/Ni Co-LDHs/NF exhibits the good HER and OER activity and stability in alkaline media.The HER overpotential is 78.3 m V,and the OER overpotential is only170 m V at the current density of 10 m A cm^-2.And the current density keeps almost unchanged after 24 h of chronoamperometric test,respectively.Using Pt/Ni Co-LDHs/NF@3D-r GO as both anode and cathode in a two-electrode system overall water splitting device,it only needs a battery voltage of 1.40 V to achieve a current density of 10 m A cm^-2,and the total potential is 1.478 V,which is similar to that of the noble metal electrocatalyst set of Pt/C||Ir/C.