Effects of Position and Electronic Nature of Substituents on Cobalt‐Porphyrin‐Catalyzed Hydrogen Evolution Reaction

Abstract

Cobalt(II) porphyrins bearing ortho/para‐amino and ortho‐nitro groups at meso‐phenyl rings have been prepared and employed for catalytic hydrogen generation. Electrochemical and catalytic studies show that position and electronic nature of the substituents strongly affect catalytic activity and overpotential of catalysis. Our study reveals that the complex with ortho‐aminophenyl substituents on porphyrin core displays higher activity toward H2 evolution with rate constant of 1.1 × 105 M−1 s−1 at onset potential close to thermodynamic reduction potential of trifluoroacetic acid (TFA), and 89% efficiency. On the other hand, the reactions involving cobalt porphyrins with para‐aminophenyl or ortho‐nitrophenyl groups showed lower or no activity under the same experimental conditions, implying the significant role of pendant ortho‐amino groups in accelerating the intramolecular proton transfer and the proton‐hydride interactions to thermodynamically favor H2 evolution.

Electrocatalytic Hydrogen Evolution of the Cobalt Triaryl Corroles Bearing Hydroxyl Groups

“…The CVs of three corrole complexes at varying scan rates (100∼400 mV s −1 ) in DMF (0.1 M TBAP) are shown in Figure S32. The peak current ( i p ) varies linearly to the square root of the scan rate ( v 1/2 ), which indicates a diffusion‐controlled electron transfer process at the electrode surface [16a,31] (Figure S32). The value of the catalyst diffusion coefficient ( D ) was determined by the following Randle‐Sevcik equation : [31b] $$$\vcenter{\openup.5em\halign{$\displaystyle{#}$\cr {i}_{p}=0.4463{n}_{p}FA{C}_{cat}{\left({{{n}_{p}FvD}\over{RT}}\right)}^{1/2}\hfill\cr}}$$$ …”

Self‐Assembled Metalloporphyrins–Magnesium Phosphate Hybrid Spheres as Efficient Catalysts for Cycloaddition of Carbon Dioxide

“…The as‐obtained hybrid materials showed enhanced enzymatic activity as well as improved stability and reusability. With the extensive studies, bovine serum albumin, papain, glucoamylase, laccase, peroxidase, and metalloporphyrins were used as organic components, while copper phosphate, manganese phosphate, cobaltous phosphate, zinc phosphate, and calcium phosphate were employed as inorganic components . And it should be noted that in many previous reports, the synergistic effects between organic and inorganic components were also observed.…”

Electrochemistry and Electrocatalytic Activity of Cobaloxime Complexes

“…In 2011 Gargi Dutta and B.D.Gupta [27] synthesized a series of inorganocobaloximes and organocobaloximes with mixed dioximes (3)(4)(5)(6)(7)(8). The mixed cobaloximes containing carbon and sulphur based ligands were reported for the first time by these authors.…”

“…[4] Since the platinum metal is highly expensive, the development of novel catalysts from the first-row transition metals has become an objective for inorganic chemists. [5] In nature, the hydrogenase enzymes like [FeFe], [NiFe], and [Fe] hydrogenases catalyze the hydrogen production reaction very effiiciently. [6,7] Based on the above reports a lot of interest has been devoted to the cost effective cobalt based catalysts.…”

“…Platinum metal is reported to be the best catalyst as it operates at the thermodynamic potential for H + /H 2 conversion [4] . Since the platinum metal is highly expensive, the development of novel catalysts from the first‐row transition metals has become an objective for inorganic chemists [5] . In nature, the hydrogenase enzymes like [FeFe], [NiFe], and [Fe] hydrogenases catalyze the hydrogen production reaction very effiiciently [6,7] .…”