Fabrication And Photoelectric Performance Research Of 1D Porphyrin-based Compounds

Porphyrins and their derivatives possess ideal structures and excellent physicochemical properties.Porphyrins are optimal components for the preparation of self-assembled nanomaterials.Porphyrin-based compounds have wide application and good development prospects in many fields such as polymer materials,chemical catalysis,electroluminescent materials,solar cells,optical energy storage devices,photoconductive materials,molecular switches,and molecular targeting.Three-dimensional metal organic frameworks(MOFs)based on porphyrins possess higher porosity and large specific surface area,which provide more active sites for catalytic applications,but the low conductivity of this metal-organic frameworks limits their application in the field of catalysis.Therefore,we constructed one one-dimensional(1D)linear porphyrin-based coordination compounds.This linear porphyrin-based coordination compounds with high electrical conductivity was synthesized via the coordination between the porphyrin macrocycle and the coordination between the metal ions and the second ligand.At the meantime,due to the strong absorption to specific wavelength for porphyrin,this one-dimensional linear porphyrin-based coordination compounds can generate photoelectrons under visible light and the photoelectrons transfer quickly via the second ligand to form photocurrent.It is significant to the design of porphyrin-based coordination compounds with high catalytic activity and excellent photoelectrochemical performance.In this paper,three different valence metal ions are separately coordinated with meso-tetraphenyl porphyrin to prepare three kinds of metalloporphyrin,and one second ligand is added to connect the metalloporphyrin to form three one-dimensional linear porphyrin-based coordination compounds.The photoelectric properties of these compounds and their application in the hydrogen evolution reaction via the electrolysis of water were investigated.1)Zirconium porphyrin(ZrTPP)is synthesized by solvothermal method to introduce the Zr4+into meso-tetraphenyl porphyrin,and one dicarboxylic acid(terephthalic acid;oxalic acid)is added in the secondary solvothermal method to coordinate with ZrTPP.The zirconium porphyrin-based coordination compounds were successfully prepared under the control of surfactant(polyvinylpyrrolidone)to morphology.A lot of long rods and sheets were observed by field emission scanning electron microscopy(FE-SEM)and transmission electron microscopy(TEM)for the zirconium porphyrin-based coordination compounds.The coordination between Zr4+ and meso-tetraphenyl porphyrin as well as the coordination between ZrTPP and second ligand were confirmed by Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),nitrogen adsorption desorption isotherm and other characterization methods.The linear scan voltammetry(LSV),electrochemical impedance(EIS),photocurrent response tests were performed by using a three-electrode electrochemical workstation.The photoelectric performance was further verified by UV/vis diffuse reflectance spectra and Photoluminescence emission spectra(PL).The results showed that the zirconium porphyrin-based coordination compounds possess high HER activity and conductivity,and it can rapidly generate photocurrent under visible light.2)The cobalt porphyrin-based coordination compounds and the iron porphyrin-based coordination compounds were synthesized by a two-step solvothermal method.The cobalt is bivalent and the iron is trivalent.It was observed by scanning electron microscopy(FE-SEM)that cobalt porphyrin(CoTPP)exhibited a large number of scattered long rods and a small amount of rectangular pyramids,and the cobalt porphyrin-based coordination compounds and iron porphyrin(FeTPP)mainly were rectangular pyramids.In addition,the morphology of FeTPP was more regular clearer ridges and smoother surface.The iron porphyrin-based coordination compounds displayed special rectangular pyramids with spine-like cross,and the surface looks like the surface of volcanic.It seems like that the special surface is formed by sculpturing the regular pyramid from the peak to bottom.Further observation by high-power transmission electron microscopy(HR-TEM)revealed that the bottom edges of the rectangular pyramids were stacked sheets.The internal structures were characterized by Fourier transform infrared spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS),powder X-ray diffraction(XRD),nitrogen adsorption desorption isotherms,etc.There is a strong link between the structures of these two coordination compounds.Moreover,the electrochemical properties of these two coordination compounds were tested and investigated.The results of polarization curves showed that the HER activity of cobalt porphyrin-based coordination compounds is close to that of zirconium porphyrin-based coordination compounds,and the HER activity of iron porphyrin-based coordination compounds is significantly superior to the above two coordination compounds.The best sample is FeTPP-OA/PVP58,exhibiting an overpotential of 83 mV at a current density of 10 mA cm-2 and a Tafel slope of 39 mV dec-1,which is very close to commercial Pt/C catalysts.In terms of photoelectrochemical performance,the iron porphyrin-based coordination compounds generated a triple photocurrent than other two coordination compounds.In addition,the electrochemical impedance results show that the three coordination compounds have extremely low conductivity and difference among them is small.In this paper,three one-dimensional linear porphyrin-based coordination compounds were synthesized by a simple and efficient strategy of two-step solvothermal method.The ideal internal structure and superior electrocatalytic activity were verified by means of various characterization methods and performance tests.It provides a novel idea and a new direction for the design of non-noble metal electrocatalysts with excellent hydrogen evolution activity and photoelectric properties.