Metallocorroles as Non‐Precious Metal Electrocatalysts for Highly Efficient Oxygen Reduction in Alkaline Media

Abstract

A series of non‐precious metal complexes, composed of five first‐row transition‐metal complexes with β‐pyrrole‐brominated 5,10,15‐tris(pentafluorophenyl)corroles [M(tpfcBr8), M=Mn, Fe, Co, Ni, and Cu], was investigated as catalysts for oxygen reduction in an alkaline solution (0.1 m KOH). The corroles were adsorbed on a high surface area carbon powder (BP2000) prior to electrochemical measurements to create a unique composite material. The comparison between the different metal complexes revealed a high oxygen reduction reaction (ORR) catalytic performance in the case of the Fe‐ and Co‐corroles. These complexes reduce oxygen at very low overpotentials (with E1/2=0.79 V and 0.77 V vs. RHE, respectively), which is better than other well‐defined molecular catalysts and comparable to that of Pt on carbon (XC‐72). The mechanism by which the most active complexes catalyze the ORR in alkaline solutions was also studied, disclosing that the dominant reaction path is a four‐electron reduction of molecular oxygen to hydroxide.

Electrocatalytically Active Silver Organic Framework: Ag(I)‐Complex Incorporated in Activated Carbon

“…Two current steps can be seen in the disk electrode, which implies on indirect ORR mechanism of 2+2 electrons, first to the formation of peroxide anion, to some extent (17 %), and later to its further reduction to hydroxide, much like in the case of the previously reported CuBTC‐based catalyst . This is also supported by the measured ring currents (Figure b), which clearly shows the formation of peroxide anion at the higher potential range, later reduced to hydroxide.…”

Carbon-Supported Copper-Based Nitrogen-Containing Supramolecule as an Efficient Oxygen Reduction Reaction Catalyst in Neutral Medium

“…Transition metal complexes generally have favorable catalytic activity for ORR, and the dispersion, deposition, or doping of these catalysts on carbon support materials substantially enhances ORR activity because of the performance improvements of many aspects of the catalysts. These aspects include high dispersion, conductivity, and an enhanced rate of mass transfer, such as charge transfer, oxygen uptake, and hydrogen uptake on the active site of the catalyst [21][22][23][24]. This type of modified catalyst is generally designated as Me-N x /C, where Me represents the complexed metal ions, N x refers to nitrogen atoms with complexing ability, and C refers to carbon materials as the supporters of the supramolecule complex.…”

“…In recent years, Me-N x /C-type catalysts have shown great potential in the practical operation of various fuel cells [25]. At present, some organic complexes formed between transition metal ions and nitrogen-containing chelating compounds have been prepared, showing an ORR catalytic performance rivaling or better than that of the Pt-based catalysts [24,25].…”

The Effects of Coordinated Molecules of Two Gly-Schiff Base Copper Complexes on Their Oxygen Reduction Reaction Performance

“…In recent decades, studies on coordination compounds have been well developed, and the developed organometallic complexes have been widely used in many fields, such as the catalysts used in the chemical and petrochemical industries [1], the molecular recognition reagents used in analytical measurements [2], and the oxygen reduction catalysts used in fuel cells [3]. Most noticeably, many new fields have been developed, such as macrocyclic coordination compounds [4], supramolecular complexes [5], metal-organic frameworks [3], and functional complexes [5]. In addition, the application of these materials as the electrocatalysts used in fuel cells have attracted a great deal of attention from both the scientific and the industrial societies due to the possibilities of replacing the precious metal platinum as the cathodic catalyst [3,4,6], ultimately endowing upon the fuel cell, a type of clean energy device, more market competitiveness than other types of energy devices.…”