One A3B Porphyrin Structure—Three Successful Applications

Abstract

Porphyrins are versatile structures capable of acting in multiple ways. A mixed substituted A3B porphyrin, 5-(3-hydroxy-phenyl)-10,15,20-tris-(3-methoxy-phenyl)-porphyrin and its Pt(II) complex, were synthesised and fully characterised by 1H- and 13C-NMR, TLC, UV-Vis, FT-IR, fluorescence, AFM, TEM and SEM with EDX microscopy, both in organic solvents and in acidic mediums. The pure compounds were used, firstly, as sensitive materials for sensitive and selective optical and fluorescence detection of hydroquinone with the best results in the range 0.039–6.71 µM and a detection limit of 0.013 µM and, secondly, as corrosion inhibitors for carbon–steel (OL) in an acid medium giving a best performance of 88% in the case of coverings with Pt-porphyrin. Finally, the electrocatalytic activity for the hydrogen and oxygen evolution reactions (HER and OER) of the free-base and Pt-metalated A3B porphyrins was evaluated in strong alkaline and acidic electrolyte solutions. The best results were obtained for the electrode modified with the metalated porphyrin, drop-casted on a graphite substrate from an N,N-dimethylformamide solution. In the strong acidic medium, the electrode displayed an HER overpotential of 108 mV, at i = −10 mA/cm2 and a Tafel slope value of 205 mV/dec.

The pH Influence on the Water-Splitting Electrocatalytic Activity of Graphite Electrodes Modified with Symmetrically Substituted Metalloporphyrins

“…A high diffusion coefficient is a desirable electrochemical property for an electrode, since the higher the value, the faster the diffusion. The obtained diffusion coefficient values are higher than the tabulated ones published by Konopka et al [ 60 ], determined using a thin-layer electrochemical cell with twin working Pt electrodes, but they are similar to the value estimated for a previously reported metalloporphyrin-modified electrode [ 44 ]. As can be seen in Table 2 , the diffusion coefficient values for the porphyrin-based electrodes are higher than that of G 0 , which means that the self-assembled aggregates present on the substrate surface enhance diffusion.…”

“…Except where otherwise stated, the current density (i) values relate to the geometric current density, while the electrochemical potential (E) values are represented vs. the reversible hydrogen electrode (RHE). The equations used to express the E values against the RHE and to calculate the values of other parameters relevant to the study, namely, the O 2 and H 2 evolution overpotentials (η O2 and η H2 ), the Tafel slope, and the electroactive surface area (EASA) [ 44 , 45 , 46 ], are shown in the Supplementary Material File as Equations (S1)–(S5) .…”

“…G0 is the unmodified graphite electrode; Table S1: The OER and HER activities of G CoP-DMSO-1 , of G ZnP-DMF-1 and of several reported electrodes. References [ 38 , 39 , 44 , 45 , 46 , 65 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 ] are cited in the Supplementary Material File.…”

Experimental and theoretical study on corrosion inhibition of mild steel by meso-tetraphenyl-porphyrin derivatives in acid solution

“…It is clear from Figure 5 that this peak reallocated after the corrosion assessment. All spectra show a remarkable change in the adsorption band, which is associated with adsorption of inhibiting molecules on XC52 mild steel surface [37,38].…”

Electrochemical Investigation of the OER Activity for Nickel Phosphite-Based Compositions and Its Morphology-Dependent Fluorescence Properties

“…In other words, from a kinetic point of view, the OER is difficult to control since it involves higher energy intermediates and multiple proton-coupled electron transfer steps [11,12]. There are materials that can serve as OER catalysts by lowering the reaction active energy, and they can be grouped into two categories: metal-based and carbon-based compounds [13][14][15].…”