Electrocatalytic Properties of Co3O4 Prepared on Carbon Fibers by Thermal Metal–Organic Deposition for the Oxygen Evolution Reaction in Alkaline Water Electrolysis

Abstract

Cobalt oxide (Co3O4) serves as a promising electrocatalyst for oxygen evolution reactions (OER) in water-electrolytic hydrogen production. For more practical applications, advances in dry-deposition processes for the high-throughput fabrication of such Co3O4 electrocatalysts are needed. In this work, a thermal metal–organic deposition (MOD) technique is developed to form Co3O4 deposits on microscale-diameter carbon fibers constituting a carbon fiber paper (CFP) substrate for high-efficiency OER electrocatalyst applications. The Co3O4 electrocatalysts are deposited while uniformly covering the surface of individual carbon fibers in the reaction temperature range from 400 to 800 °C under an ambient Ar atmosphere. It is found that the microstructure of deposits is dependent on the reaction temperature. The Co3O4 electrocatalysts prepared at 500 °C and over exhibit values of 355–384 mV in overpotential (η10) required to reach a current density of 10 mA cm−2 and 70–79 mV dec−1 in Tafel slope, measured in 1 M KOH aqueous solution. As a result, it is highlighted that the improved crystallinity of the Co3O4 electrocatalyst with the increased reaction temperature leads to an enhancement in electrode-level OER activity with the high electrochemically active surface area (ECSA), low charge transfer resistance (Rct), and low η10, due to the enhanced electrical conductivity. On the other hand, it is found that the inherent catalytic activity of the surface sites of the Co3O4, represented by the turnover frequency (TOF), decreases with reaction temperature due to the high-temperature sintering effect. This work provides the groundwork for the high-throughput fabrication and rational design of high-performance electrocatalysts.

Elevating Supercapacitor Performance of Co3O4-g-C3N4 Nanocomposites Fabricated via the Hydrothermal Method

“…The lattice parameters hkl plan (400) of the XRD were well matched with the SAED pattern represented in Figure 5 d by the yellow ring. Similar results were reported by M. G. Kim et al [ 32 ] and M. Xlao et al [ 33 ]. The Co 3 O 4 -g-C 3 N 4 -150 mg nanocomposite’s elemental composition has been identified using energy-dispersive X-ray spectroscopy (EDS).…”

Nanoengineered Cobalt Electrocatalyst for Alkaline Oxygen Evolution Reaction

“…The formation of cobalt hydroxide on the surface occurred due to the high oxophilicity of cobalt and surface reconstruction during the DHBT synthesis. The active sites for oxygen evolution reaction in the synthesized electrocatalysts were identified to be Co(OH) 2 surface species and cubic Co 3 O 4 in agreement with previous reports [ 24 , 55 , 56 ].…”

“…To further investigate the phase composition, synthesized cobalt electrocatalyst were characterized using a Raman spectrometer using a 532 nm laser and the collected data is shown in Figure 3 e. Raman characterization confirmed the presence of cubic phase Co 3 O 4 in all the electrodeposited samples. The four peaks identified in the Raman spectra at 479, 520, 614, and 682 cm −1 were assigned to the Raman active modes of E g , F 2g , F 2g , and A 1g for cubic Co 3 O 4 in agreement with the previously published literature [ 54 , 55 , 56 ]. The highest Raman intensities were observed for Co@Cu-30 which had the highest cobalt content and the lowest oxygen content as determined from the EDX analysis.…”

Investigation of Ionomer and Catalyst (Co3O4, Mn3O4, or MnO2) Interactions Using a Polyethylene Midblock Copolymer in Anion Exchange Water Electrolyzers to Understand Performance and Durability

“…2 and Table I) In contrast, the OER Tafel slope of the cobalt oxide with 1 M KOH electrolyte using rotating disk electrode (RDE) are 70 to 79 mV dec −1 , which is as expected to be lower than the cell due to difference in pH, no inclusion of HER and no mass transport limitation. 39 Despite abovementioned potential of cobalt oxide nanoparticles as an OER electrocatalysts, a higher loading of cobalt oxide that owes a tendency to agglomerate which causes loss of surface area and therefore loss of activity. 40,41 Also, the agglomerated cobalt oxide nanoparticles in the absence of an adequate amount of ionomer to establish ion-conducting pathways and the electrical conductivity assisted by Ni-foam was fully blocked for 4.5 mg cm −2 , tends to act as an insulator.…”