Surface Reconstruction And Application Of Transition Metal Phosphides In The Electrocatalytic Conversion Of 5-Hydroxymethylfurfural

5-Hydroxymethylfurfural（HMF）is a kind of biomass material with wide souses.Its oxidation product 2,5-furan dicarboxylic acid（FDCA）is now attracted extensive attention from industry and academia due to its commercial value,and the U.S.Department of Energy also classified FDCA as"Top Value Added Chemicals From Biomass".At present,non-precious electrocatalysts such as metal phosphides have shown extraordinary performance.However,their non-precious metals are not stable under high p H and a strong oxidation environment,and they are more likely transformed into their corresponding oxides and（oxy）hydroxides during the catalytic process.In this paper,the high performance NiFeP catalyst is the main research object.The transformation of the active moieties during the catalytic process was revealed by the in-situ Raman spectra and experiment results show that in-situ formed hydroxide is the true active moieties.Meanwhile,this paper also proposed the"dual cycle"mechanism which reveals the competitive relationship between HMF oxidation and water oxidation on the nickel based catalysts.Under the guidance of the surface reconstruction of NiFeP during HMFOR,we de designed a kind of core@shell suture NiFeP@NiFe（OH）_x catalyst which shows better HMFOR performance.（1）The surface reconstruction of metal phosphides during the HMFOR and OER process was studied with NiFeP catalyst.And revealed the competitive relationship between HMF oxidation and water oxidation on the Nickel based catalysts.The"dual cycle"mechanism shows that the reversible conversion between NiOOH and NiOO₂ can gradually oxidize OH^-to O₂（electrochemical process）,in the HMFOR process,HMF alco can gradually oxidize to FDCA through the reversible conversion between Ni（OH）₂ and NiOOH（non-electrochemical process）.When HMF is sufficient in the electrolyte,HMF will consume NiOOH and reduce NiOOH to Ni²⁺,HMF also be oxidized to FDCA during this process.However,when the HMF is insufficient or the potential increases further,the catalyst will be further oxidized to NiOO₂,and the OH^-in the solution will gradually occupy the active sites and start OER.（2）Prepared NiFeP@NiFe（OH）_x catalyst which has the same structure as post-HMFOR NiFeP.NiFe（OH）_x shows 90.78%FDCA yield and Faradaic efficiency of electrooxidation from HMF to FDCA.However,the newly designed NiFeP@NiFe（OH）_xcatalyst shows better FDCA yield（94.02%）and Faradaic efficiency（94.42%）,and the performance of NiFeP@NiFe（OH）_x catalyst does not change during three consecutive HMFOR tests.Transmission electron microscopy images and Raman spectra show that the structure of NiFeP@NiFe（OH）_x catalyst can keep stable after long-time electrochemical test.