Construction And Electrocatalytic Oxygen Evolution Performance Of Self-surported Copper-based Nanoarrays

In the process of searching for new energy to solve the energy crisis and environmental pollution problems,hydrogen energy has become an ideal clean energy to replace fossil fuels due to its high energy density.Among the existing hydrogen production technologies,the sustainability of electrochemical water splitting technology using water as raw material has attracted extensive attention of researchers.Under the restriction of the energy barrier,the study of electrocatalyst is the key to determine the efficient application of electrochemical water splitting technology.The current state-of-the-art OER electrocatalyst are noble metal oxides Ir/Ru O_x,however,their large-scale production is hindered by resources and cost.Therefore,it is of great significance to design promising non noble metal electrocatalysts.Here,copper-based materials with good conductivity but low catalytic activity were improved through two aspects:material composition and morphology regulation.Several kinds of self-supporting Cu based nano array electrocatalysts with remarkable catalytic activity and excellent stability were fabricated on the copper foam substrate.The application performance for OER and the structural transformation after long-term reaction of the catalysts were analyzed.And these researches provide new strategies for the rational design of electrocatalysts.The contents are as follows:（1）Using copper foam as both substrate and copper source,the vertically self-supported copper hydroxide nanorods were prepared by electrochemical anodization approach,which were combined with 2D nanosheets Metal Organic Frameworks ZIF-Co via solvothermal method to fabricate ZIF-Co/Cu（OH）₂/CF nanoarrays.Benefiting from the constructed hierarchical heterostructure and the large specific surface area morphology of the nanosheets on the rods,ZIF-Co/Cu（OH）₂/CF shows outstanding OER catalytic performance.In 1.0 M KOH alkaline electrolyte,only 236 m V overpotential is required to achieve the current density of 100 m A cm^-2.The characterization of the post electrode products experienced long-term OER operation of 67 hours shows that the catalyst still present stable catalytic activity despite the oxidation.This catalytic electrode with promising application potential also provides a new idea for the design of copper-based catalysts.（2）The trimetallic phosphide Co-Fe-P/Cu₃P/CF nanoarrays with Prussian blue analogue（PBA）as precursor were synthesized on Cu（OH）₂/CF prepared in the previous chapter via ion exchange and vapor deposition methods.The obtained electrode only needs an overpotential of 205 m V to reach the current density of 100m A cm^-2;and it can maintain stable catalytic activity for at least 60 h.The prominent catalytic performance is mainly attributed to the construction of the unique morphology,in which the rod-shaped structure can promote the transportation of the reactants;and the hollow structure as well as the nanosheets outside can expand the specific surface area.Besides,the electronic interaction between multiple metals can also improve the conductivity of the catalyst.The characterization analysis of the post electrode after water splitting reaction imply that the surface of the material was partially oxidized to the corresponding oxide,which can generate new active sites to maintain the high catalytic activity together with the residual phosphide.Our research may provide a new reference for the fabrication of PBA-based materials applied in electrochemical energy conversion and storage.（3）Fe-Ni-Se/Cu（OH）₂/CF nanoarray electrocatalyst with core-shell structure was fabricated on Cu（OH）₂/CF by the facial electrodeposition operation.The combination of Fe-Ni-Se with high conductivity and Cu（OH）₂ with vertical nanorod structure constructs the interface engineering in Fe-Ni-Se/Cu（OH）₂/CF,which can significantly improve the OER catalytic performance of the composite,so that it can reach the current density of 10 m A cm^-2 with only 233 m V overpotential,lower than the most reported non noble metal electrocatalysts and the commercial noble metal oxides.The characterization of the product after the reaction revealed the surface reconstruction of Fe-Ni-Se/Cu（OH）₂/CF,including the formation of Fe OOH and Ni OOH with classy adsorption capacity,and the fluffy core-shell structure with ultra-thin nanosheets.In this work,the construction of interface engineering and the analysis of surface reconstruction provide insight for the deeply study of the mechanism of OER electrocatalyst.