Beneficial Effects on the Cobalt-Catalyzed Hydrogen Evolution Reaction Induced by Corrole Chelation

Abstract

Current technologies for the mass production of hydrogen gas, needed for fuel cells, the synthesis of ammonia, and many other purposes, have an enormous carbon footprint. Less than 5% of H 2 is manufactured by the much cleaner water electrolysis process, mainly because electrodes are based on precious platinum. In line with the worldwide effort of replacing platinum by earth-abundant metals, this study focused on electrocatalytic proton reduction by cobalt. A series of cobalt(III) corroles that greatly varies in the electronic and steric effects of the meso-C substituents was fully characterized for investigating how the complexes differ in terms of their reduction potentials and as electrocatalysts for proton reduction to hydrogen gas. The smallest and most electron-rich derivative, with H atoms rather than larger and more electron-withdrawing substituents on the macrocycle, displayed the most interesting catalytic activity. Despite of its most negative Co II /Co I reduction potential in the absence of acid, catalysis by this complex was characterized by the lowest overpotential and the largest faradaic efficiency, as well as an activity that was almost as good as that of platinum under heterogeneous conditions. Mechanism-of-action investigations via experimental and computational analyses exposed that the superior performance of the most electron-rich complex is attributable to its capability of reducing protons by singly (rather than doubly) reduced cobalt.

Electrocatalytic Hydrogen Evolution of Transition Metal (Fe, Co and Cu)–Corrole Complexes Bearing an Imidazole Group

“…Other parameters of the three corroles at TFA and TsOH are summarized in Tables S2 and S3. To compare the HER activity of PFIC-Co, PFIC-Cu, and PFIC-Fe with other molecular electrocatalysts, the previously reported HER activities of some transition metal molecular electrocatalysts are summarized in Table S4 [28,31,[46][47][48][49][50]. The table shows that the performance of these molecular catalysts is diverse.…”

“…Electrochemical hydrogen production pathways are generally inseparable from proton transfer and electron transfer processes, and most of the active center is metal [51]. Based on previous reports on electrocatalytic hydrogen production by metal corroles [47,48], the speculated catalytic pathways of the current system are depicted in Scheme 2. For PFIC-Co, when the proton source is the weak acid AcOH, Co II /Co I gradually becomes irreversible with the increase in acid concentration, suggesting that Co I is involved in the HER.…”

Design and Development of Sustainable Cu2 (II)- and Mn2 (III)-Embedded Bifunctional Electrocatalysts: Enhanced Hydrogen and Oxygen Generation

“…Considering the increasing future energy requirements and the ensuing environmental repercussions, there is a crucial need to address the substantial carbon imbalance in the usage of fossil fuels. As a result, there is a worldwide expectation of shifting toward cleaner and sustainable energy sources to supplant carbonaceous fuels. − From this perspective, hydrogen may be regarded as the most potentially sustainable energy fuel as it emits no carbon dioxide during its combustion and is widely employed as a future energy source. , Over the last three decades, a possible method for creating effective, carbon-free, sustainable energy and its storage has been the electrocatalytic water-splitting reaction to generate molecular hydrogen and oxygen. − Green energy can be produced cleanly and continually through the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), and these reactions occur at the anode and cathode of the alkaline electrolyzer employed for water splitting, respectively. OER and HER both take place concurrently .…”

Switching Electrocatalytic Hydrogen Evolution Pathways through Electronic Tuning of Copper Porphyrins

“…[10][11][12][13][14][15][16][17] These efforts not only led to the identification of a variety of metal complexes as highly efficient electrocatalysts for HER, [18][19][20][21][22][23][24][25] but also provided valuable results to correlate the catalytic HER activities of metal complexes with their electronic structures. [26][27][28][29][30][31][32] Despite these achievements, however, switching the HER mechanism in a controllable manner through electronic tuning of metal complexes is rarely presented. Controlling HER mechanisms and understanding the dependence of mechanisms on catalyst electronic structures are of fundamental significance and also can provide the basis for rational catalyst design.…”