Fabrication Of Graphite Foam Based Composites As Self-standing Electrode For Electrochemical Applications

The graphite foam(GF)is featured with abundant of macro pores,large SSA and good electric conductivity,thus has been used widely in the electrochemistry field.Using 3D GF as the electrode support,more active catalysts located inside the porous structure can contact directly with the electrolyte or reactants,which will increase the utilization efficiency of the active centers.Herein,the dip-coating and in-situ supporting methods are involved to fabricate kinds of GF-based self-supporting electrodes.The as-prepared electrodes were then employed as the catalyst in water splitting process and advanced oxidation process(AOPs),and showed remarkable catalytic activities.Using the dip-coating method,few-layered tungsten disulfide(WS₂)with a controlled phase ratio(the highest trigonal phase ratio of 67%)was exfoliated via lithium insertion.The exfoliated WS₂ nanosheets were then anchored onto three dimensional(3D)graphite foam(GF)to fabricate free-standing binder-free electrodes.The 3D GF can increase the interfacial contact between the WS₂ nanosheets and the electrolyte and facilitate the ion transfer.Without non-conductive binder,an intimate contact between the WS₂ and GF interface can be created,leading to the improvement of electrical conductivity.Compared to the pure WS₂ nanosheets,the overpotential for hydrogen evolution reaction is significantly decreased from 350 m V to 190 m V at 10m A/cm²,and no deactivation occurs after 1000 cycles.The density functional theory computations reveal that the efficient catalytic activity of the trigonal phase WS₂/GF electrode is attributed to the lower Gibbs free energy for H*adsorption and optimized Femi level.In the other work,nitrogen-doped graphene quantum dots(N-GQDs,?5 nm)were synthesized and supported on graphite foam(GF)by a facile in situ hydrothermal route.The obtained N-GQDs/GF composite can be used as an ultra-active free-standing electrode for electrochemical hydrogen evolution(HER),which could also activate the peroxymonosulfate(PMS)to degrade phenol under the assistant of cyclic voltammetry.The overpotential for HER process is only-72 m V vs.RHE at 10 m A/cm² with a Tafel slope of 84 m V/Dec.The N-GQDs/GF electrode can also achieve 100%phenol removal in short time during the electrochemical degradation process.Furthermore,we fabricated a nitrogen and sulfur co-doped graphene(SNG)anchored on the interconnected conductive graphite foam(GF)via drop-casting and in situ annealing.The SNG flakes are tightly immobilized on the GF surface,which can provide high electron transfer rate and large electrolyte/electrode interfaces.The free-standing SNG@GF composite can be directly used as a metal-free electrocatalytic electrode for water splitting and electrocatalytic degradation of aqueous organic pollutants.The SNG@GF composite electrode exhibits an initial overpotential of 330m V vs.RHE at 10 m A cm^-2 with a Tafel slope of 149 m V dec^-1 in 1 M KOH,the performance of which outperforms the other metal-free catalysts in oxygen evolution reaction.Moreover,the SNG@GF composite exhibits enhanced reactivity for electrochemical activation of peroxymonosulfate to oxidize the phenolic contaminants in water,and the electricity was only effective for the radical process enhencement.The density functional theory computations unveil the protocols of carbocatalysis in enhanced catalytic reduction reactions,further verify the mechanism of the advanced catalytic activity.It has been proved based on our research work that the CVD generated GF shows special three-dimensional porous structure,excellent electrical conductivity and good chemical stability.Using GF as the carbon support,considerable catalytic activity in new energy development and environmental remediation could be achieved,thus should have great potential in the real application.