Design Of Transition Metal Co-Based Nanomaterials And Study On Electrocatalytic Properties

With the continuous adjustment of the social economy and energy policy,the proposal of“double carbon target”is particularly critical and has gradually become a global consensus.At this time,it is particularly important to developing a green,low-carbon,environmentally friendly,and sustainable technology to develop new energy sources.Electrocatalysis has attracted much attention due to its key role in the preparation,storage,and conversion of clean energy.Transition metal Co-based materials have many electronic settings and rich forms,and have many development advantages such as abundant reserves,low cost,and high activity potential.Although great efforts have been made to improve the catalytic performance of cobalt-based nanostructures,their catalytic performance is still unsatisfactory due to the low conductivity.To study new Co-based materials with high activity and high stability,we try to design and optimize the following strategies:（1）Constructing heterogeneous interface,improving electronic coordination and optimizing electronic structure.（2）Doping heterometallic atoms,improving the intrinsic activity of electrocatalysts,and reducing theΔG_H*of catalytic materials.（3）Composite conductive substrate,improving the conductivity of the material,and solving the complex problem of electrode preparation faced by traditional powder materials.Based on the above optimization strategies,Co Ox/Co P-L,Ru@Fe Co P,Ru Co Cu-MOF/CF catalyst materials were designed and constructed in this paper,and they were effectively applied in electrocatalytic hydrogen evolution reaction（HER）,oxygen evolution reaction（OER）,urea oxidation（UOR）and overall water splitting（OWS）.The main research contents are as follows:1.Co Ox/Co P-L with excellent economic benefits and excellent hydrogen evolution performance was synthesized by phosphorization-freezing treatment,innovatively realizing the effective regulation of crystal/amorphous interface and strain structure of cobalt-based precursors.Worthily,the rapid freezing treatment causes the lattice of the material to be distorted,which is one of the keys to the significant improvement of material properties.The experimental and theoretical results show that the amorphous/crystalline heterogeneous interface optimizes the adsorption/dissociation energy of water,and the twisted lattice fringes can optimize the electronic structure of Co Ox/Co P-L,effectively reducing theΔG_H*of alkaline HER,thereby increasing the speed of HER processthe.Under alkaline and acidic conditions,the well-designed Co Ox/Co P-L catalyst requires only an overpotential of 56.6 m V and 98 m V to drive a current density of 10 m A cm^-2,respectively.At a current density of 68 m A cm^-2,the catalytic activity of Co Ox/Co P-L began to exceed that of commercial Pt/C electrode,showing excellent catalytic potential.2.Ru nanoparticles were successfully anchored on the double-shell Fe Co P prism by ion exchange-phosphorization-photodeposition three-step method,and Ru@Fe Co P electrocatalyst with rich Ru/Fe Co P heterogeneous interface was constructed.The mechanism study found that the Ru atom on the Ru/Fe Co P heterostructure not only provides a highly active site for HER,but also absorbs electrons from Fe Co P,promotes the formation of high valence Fe and Co,optimizes the adsorption capacity of the intermediate,and improves the OER activity,thus realizing the dual active site mechanism.The well-designed Ru@Fe Co P sample has an overpotential of only 0.0741 V for HER and 0.314 V for OER at 100 m A cm^-2,which is 1.76 times and 1.23 times lower than the Pt/C and Ru O₂benchmarks,respectively.3.Ru Co Cu-MOF nanorods（Ru Co Cu-MOF/CF）with adjustable cavity were designed and synthesized on copper foam（CF）substrates by self-sacrificing template strategy as bifunctional catalysts for HER and UOR.The unique hollow nanorod structure and the optimal cavity size give the catalyst a large active specific surface area and hydrophilic surface,promoting the mass transfer process of the catalyst.Worthily,the formed Ru-O-Co bond bridge provides a channel for the directional flow of electrons from Ru to Co atoms,and adjusts the electronic configuration of the material.At the same time,the Ru and Co atoms with the best electronic configuration can synergistically promote the adsorption and dissociation of intermediates,thereby greatly accelerating the dissociation of water and the release of hydrogen.Under the action of internal and external regulation,the high-efficiency and energy-saving HER||UOR electrolyzer only needs a voltage of 1.402 V to drive a current density of 10 m A cm^-2,representing the highest level of overall water splitting performance under alkaline conditions.In addition,during the HER process,the Ru Co Cu-MOF electrocatalyst with a trace amount of Ru can reach an ultra-low overpotential of 11.6 m V at 10 m A cm^-2,which is 2.21 times that of commercial Pt/C/CF.At the same time,Ru Co Cu-MOF/CF also exhibits an ultra-low onset potential of 1.32 V in UOR.The design of Ru Co Cu-MOF/CF provides the possibility for cobalt-based MOFs to be directly used as an integrated hydrogen production-decontamination electrode.