Preparation And Research Of Micro-nano Hierarchical Porous Water Decomposition Catalytic Material

Due to the limited fossil storage and the pollution issues,hydrogen energy attracts considerable interest as a renewable,clean and efficient energy.Water splitting is a fast and pollution-free way to produce hydrogen.It requires the application of catalyst to reduce the over potentials for hydrogen and oxygen revolutions.However,the commercial Ni-based catalysts exhibit low stability during catalysis and the over-potentials for hydrogen and oxygen revolutions are much higher than that on noble-element-based catalysts,such as Pt and Ru O₂.Therefore,this research intend to develop new porous catalysts with improved stability and catalytic activity by hydrogen bubble template（DHBT）deposition.Firstly,porous Ni-Co-Cu ternary coatings were prepared by DHBT co-deposition.The influence of plating solutions,deposition parameters and activation process on the composition,morphology and catalytic performance of the porous Ni-Co-Cu ternary coatings.The results show that the 0.1 M Ni SO₄+0.1 M Co SO₄+0.03 M Cu SO₄+0.5 M（NH₄）₂SO₄+0.3 M Na₃C₆H₅O₇+0.4 M H₃BO₃ formula by applying a cathode current density of-1 A/cm² for 60 s.After activation,the catalyst exhibited high activity towards hydrogen evolution,i.e.,the over-potential for hydrogen evolution at 10m A/cm² is 74 m V,and the Tafel slope is 71.7 m V/dec.The outstanding catalytic activity was attributed to the high electrochemical active area of the catalyst,the metal-metal oxide core-shell structure formed on the surface of the catalyst during activated,and the interaction between Co,Ni and O in the oxide shell.However,the catalytic stability was relatively low.Therefore,the composition of the as-deposited Ni-Co-Cu was further tuned towards a ternary middle-entropy alloy.The contrast showed that the catalytic stability of a middle-entropy alloy is much higher.Secondly,porous Ni-Co-Fe-Cu quaternary middle-entropy coatings were prepared by DHBT co-deposition.Based on the selection of additives,a series of middle-entropy Ni-Co-Fe-Cu coatings were prepared.By tuning the plating solutions and deposition parameters,the middle-entropy coatings with 23.10 at%of Ni,23.10 at%of Co,23.10at%of Fe,23.10 at%of Cu with good catalytic performance was obtained.It was noting that the over-potential for oxygen evolution on the catalyst is only 257 m V under the current 10 m A/cm²,much lower than that on Ru O₂（277 m V）.The Tafel slope is 40.5m V/dec.Moreover,after 1000 times of cyclic voltammetry cycles in 1 M KOH,the catalyst still maintain high catalytic activity.Finally,the quaternary middle-entropy coating was phosphating to further improve the catalytic performance towards water splitting.It was found that when compared with the as-deposited coating,the phosphating sample displayed higher catalytic activity towards both hydrogen evolution and oxygen evolution.Though the hydrogen evolution over-potential is 112 m V,and the Tafel slope is 92.4 m V/dec at 10 m A/cm².The over-potential at 40 m A/cm² became lower than the as-deposited sample.The oxygen evolution over-potential is only 243 m V,and the Tafel slope is 52.7 m V/dec.The improvement of catalytic performance is attributed to the increase of electrochemically active area and the strong electronegativity of P.