Spinel-Type Metal Oxide Nanoparticles Supported on Platelet-Type Carbon Nanofibers as a Bifunctional Catalyst for Oxygen Evolution Reaction and Oxygen Reduction Reaction

Abstract

Development of highly active bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is required for air electrodes of zinc-air secondary batteries (ZAB). In this study, we synthesize spinel-type MnCo 2 O 4 (MCO) nanoparticles on highly graphitized platelet-type carbon nanofibers (pCNF) via a solvothermal method. The pCNF is selected as carbon support in this study because of the excellent stability against anodic degradation under the OER condition. The MCO nanoparticles of 2-5 nm in diameter are uniformly dispersed on pCNF and the catalyst exhibits high activities for ORR due to strong interaction pCNF and MCO, in addition to the improvement of OER activities. The MCO/carbon hybrids show comparable electrocatalytic performances to state-of-the-art bifunctional electrodes for OER and ORR.

Electrocatalytic Properties of a BaTiO3/MWCNT Composite for Citric Acid Detection

“…MWCNT-based materials have been used to fabricate cocatalysts and support many catalytic applications. According to Sato et al, carbon-supported metal-oxide composites show excellent electrocatalytic performance owing to the tuned electronic states of catalysts [50]. Therefore, combining carbon materials and metal oxides can enhance the catalytic process [51][52][53].…”

History of ECSJ Awards and Introduction of Award Winners in 2021

“…Aoki has made pioneering research achievements in the development of novel electrode and electrolyte materials for protonic ceramic fuel cells and steam electrolyzers, 34 as well as in the operating principles of devices constructed by combining these materials. [35][36][37] Recently, he contributed the articles for hydrogen permeability of metal nitrides membranes with hydridic defects in society journal. 38 Another awardee, Shiraishi is currently a professor of Gunma University.…”

High-corrosion-resistance mechanism of graphitized platelet-type carbon nanofibers in the OER in a concentrated alkaline electrolyte

“…Carbon is one of the key components in electrochemical energy conversion and storage systems, such as lithium-ion batteries, [1][2][3][4][5][6] electrochemical capacitors, [7][8][9][10][11][12][13][14][15] polymer electrolyte fuel cells (PEMFCs), [16][17][18][19][20][21][22][23] and metal-air secondary batteries (MABs). [24][25][26][27][28][29][30][31] However, carbon materials suffer from electrochemical oxidation; that is, carbon corrosion occurs in aqueous electrolytes at high anodic potentials, where many important electrochemical reactions, including the oxygen evolution reaction (OER), transpire. The thermodynamic instability of carbon is evident from the low equilibrium potential of carbon oxidation to CO 2 at 0.207 V vs. SHE at 25 C. 32 The carbon oxidation reaction (COR) in alkaline electrolytes proceeds through two elementary steps via the following reactions: 24,[32][33][34][35][36][37][38] C + 4OH À / CO 2 + 2H 2 O + 4e À…”

“…The COR induces electrode degradation because of the loss or agglomeration of electroactive species on carbon or the loss of electro-conductive paths when using carbon materials as the electrocatalyst support or conductive additive. [16][17][18][19][23][24][25][26][27][28][29][30][31] When OER electrodes with noble-metal-free electrocatalysts were fabricated, a carbon material was oen added as a conductive support because of the insufficient electrical conductivity of electrocatalysts. [29][30][31] For developing durable OER electrodes, the COR of the carbon conductive support must be avoided.…”

“…[16][17][18][19][23][24][25][26][27][28][29][30][31] When OER electrodes with noble-metal-free electrocatalysts were fabricated, a carbon material was oen added as a conductive support because of the insufficient electrical conductivity of electrocatalysts. [29][30][31] For developing durable OER electrodes, the COR of the carbon conductive support must be avoided. Carbon materials have advantages compared to other conductive materials from the following viewpoints: (i) earth-abundance, (ii) light weight, (iii) reasonable electrical conductivity, and (iv) oxygen reduction reaction co-catalysis activity, which is the crucial characteristic of the air electrode in the metal-air secondary battery system.…”