Preparation Of Cobalt-Based/Carbon Foam Composites And Research Of Their Electrolytic Water Performance

The excessive consumption of fossil energy and the consequent environmental pollution have seriously affected human work and life.As a renewable and clean energy with high energy density,hydrogen has attracted more and more attention of scientific researchers.Among the various hydrogen production technologies,electrocatalytic hydrolysis can achieve large-scale and sustainable production of high-purity hydrogen and oxygen.Among them,efficient,stable and low-cost electrocatalysts are the key factors for the development of electrolytic water hydrogen production technology.In this paper,a series of cobalt-based/carbon foam composite electrocatalysts were prepared and their electrocatalytic performance was evaluated based on the principle of cost reduction and resource conservation with non-precious metal cobalt-based materials as the main research object.The main research contents and conclusions are as follows:（1）A nitrogen-doped carbon nanotube-enhanced three-dimensional self-supporting electrocatalyst（Co/NCNT@CF）was prepared by a simple impregnation and pyrolysis method using a very low-cost melamine foam as the precursor substrate.The catalyst exhibits rare flexibility,can be flexibly bent and recovered,and has good catalytic performance for both hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）in alkaline electrolytes.The Co/NCNT@CF-800 catalyst obtained at the optimal pyrolysis temperature requires an overpotential of 183 and 305 m V to drive a current density of 10 m A cm^-2 when applied to HER and OER,respectively.The material also has good stability in both HER and OER processes,maintaining high catalytic activity after20 h of continuous operation at a current density of 10 m A cm^-2.The excellent performance can be attributed to:the network structure of the carbon foam inhibits the agglomeration of the nanoparticles synthesized in situ,which maximizes the efficiency of the catalytically active material;the electrode material is prepared without the use of a binder,which effectively avoids the blockage of the metal active center,thus improving the mass transfer and utilization of the accessible active sites;the structure of the carbon-coated metal nanoparticles is beneficial to improve the stability of the catalyst material in strong alkaline environment.（2）A three-dimensional composite（Co P/Co₂P/NCNT@CF）with the coexistence of Co P and Co₂P was successfully prepared by a two-step strategy of high-temperature carbonization and low-temperature phosphorylation.The composite is based on a three-dimensional macroporous carbon foam skeleton,which provides a fast channel for mass and charge transfer.The hollow structured polyhedra loaded on the foam carbon skeleton facilitate the exposure of more active sites.Therefore,the composite can be used as a bifunctional high-efficiency electrocatalyst for HER and OER.The electrochemical test results showed that the overpotentials of HER and OER in 1 M KOH solution at 10 m A cm^-2 current density were 133 and 289 m V,respectively.In addition,the catalyst material also has excellent long-term stability,with both reaction processes being stable at a current density of 10 m A cm^-2 for at least 20 h.These results indicate that the Co P/Co₂P heterostructure leads to a significant improvement in the intrinsic activity of this catalyst through the interfacial coupling effect.Meanwhile,due to the tight connection of the components in the in situ grown catalyst with the carbon foam substrate,the agglomeration or shedding of the active material was effectively prevented,and the HER and OER performance of the catalyst was enhanced.In summary,the electrocatalyst synthesized in this work has the advantages of low cost,high activity and good stability,which provides a new idea for the design and development of non-precious metal catalysts.