Electrocatalytic Hydrogen Evolution By Iron Complexes Of Corrole And Porphyrin

The usage of fossil fuels in industrial development has made environmental pollution problems serious day by day,and people found that clean energy as a substitute is the general trend.Hydrogen attracts people's attention because of its renewable,non-polluting,large heat value,easy storage and transportation.It begins to gradually replace the position of fossil fuel in industrial production.In the case of increased demand for hydrogen,electrolyzing water is a very efficient method of obtaining hydrogen,and the use of a catalyst can reduce the consumption of electrical energy in the production process.In this paper,two types of catalysts for catalytic hydrogen production are designed and tested for their properties:Through "one-pot and two-step method" and"one-pot method"respectively,5,10,15-tris?pentafluorophenyl?corrole?TPFC?and 5,10,15,20-tetra?pentafluorophenyl?porphyrin?TPFP?were synthesized at the room temperature.And their iron complexes were obtained correspondingly.Their structures were characterized by ultraviolet-visible spectroscopy,high resolution mass spectrometry and nuclear magnetic resonance spectroscopy.When the overpotential was 942 mV vs SHE?Standard hydrogen electrode?,the turnover frequency of Fe?TPFC?Cl was 19.79 h^-1,with acetic acid as the proton source in the organic phase by electrochemical tests,while the TOF value of Fe?TPFP?Cl was 14.36 h^-1;and in the aqueous phase,the TOF value of Fe?TPFC?Cl and Fe?TPFP?Cl were significantly increased to274.2 and 233.1 h^-1 respectively when the overpotential was 838 mV vs SHE with water as the proton source,the Faraday efficiencies were 96%and 93%,respectively.By controlled potential electrolysis continuously for 72 hours,neither of the two complexes decomposed,which manifested that the stability of these catalysts were very good.Combined with previous reports,it was speculated that the hydrogen production process electrocatalyzed by Fe?TPFC?Cl and Fe?TPFP?Cl were different:?1?in the hydrogen production process,Fe?TPFC?Cl first obtained two electrons and then protonated to Fe???-H intermediate,then two Fe???-H underwent bimolecular homogenization to release hydrogen;?2?Fe?TPFP?Cl became Fe?0?intermediate after obtaining three electrons,and formed as Fe???-H metal hydride after protonation.the Fe???-H intermediate was obtained through the electron reduction reaction,and reacted with a proton,hydrogen was released after the heterolysis.