VO2 as a Highly Efficient Electrocatalyst for the Oxygen Evolution Reaction

Abstract

Herein, we report high electrocatalytic activity of monoclinic VO2 (M1 phase) for the oxygen evolution reaction (OER) for the first time. The single-phase VO2 (M1) nanoparticles are prepared in the form of uniformly covering the surface of individual carbon fibers constituting a carbon fiber paper (CFP). The VO2 nanoparticles reveal the metal-insulator phase transition at ca. 65 °C (heating) and 62 °C (cooling) with low thermal hysteresis, indicating a high concentration of structural defect which is considered a grain boundary among VO2 nanoparticles with some particle coalescence. Consequently, the VO2/CFP shows a high electrocatalytic OER activity with the lowest η10 (350 mV) and Tafel slope (46 mV/dec) values in a 1 M aqueous solution of KOH as compared to those of the vacuum annealed V2O5 and the hydrothermally grown VO2 (M1), α-V2O5, and γ′-V2O5. The catalytically active site is considered V4+ components and V4+/5+ redox couples in VO2. The oxidation state of V4+ is revealed to be more favorable to the OER catalysis compared to that of V5+ in vanadium oxide through comparative studies. Furthermore, the amount of V5+ component is found to be increased on the surface of VO2 catalyst during the OER, giving rise to the performance degradation. This work suggests V4+ and its redox couple as a novel active component for the OER in metal-oxide electrocatalysts.

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

“…State-of-the-art OER catalysts are based on precious metals such as IrO 2 and RuO 2 with the η values from 200 mV (in acid) to 300 mV (in base), but the scarcity and high costs of those materials restrict their large-scale applications [ 7 ]. In this regard, the earth-abundant transition metal oxides based on Co, Ni, Fe, and V have been extensively investigated as alternative OER catalysts [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ].…”

Immobilization of molecular complexes on graphitized carbon cloth as stable and hybrid electrocatalysts for enhanced hydrogen evolution reaction and oxygen evolution reaction

“…The ECSA was determined from eqn (2), and the double-layer capacitance current is directly proportional to the electrochemical active surface area (ECSA). 31 The linearity obtained from the plot of geometrical current density and scan rate revealed a diffusion-controlled electrocatalytic process. The facile electron flow in the process is due to diffusion.where Δ j is current density (mA cm −2 ), and V is potential.…”

“…The electrochemical active surface area (ESCA) is a good descriptor of the electrochemical activity toward hydrogen evolution reaction. The ECSA was determined from equation 2, double-layer capacitance current is directly proportional to the electrochemical active surface area (ECSA) 31 . The linearity obtained from the plot of geometrical current density and scan rate revealed a diffusion-controlled electrocatalytic process.…”

Graphitic Carbon Cloth-Based Hybrid Molecular Catalyst: A Non-conventional, Synthetic Strategy of the Drop Casting Method for a Stable and Bifunctional Electrocatalyst for Enhanced Hydrogen and Oxygen Evolution Reactions

“…From Figure a, it is observed that the hybrid electrocatalysts showed a C dl value of 60.06, 154.2, and 60.92 mF cm –2 respectively. The electrochemical activity is well interpreted through the electrochemical active surface area (ESCA), which is directly proportional to the double-layer capacitance . The linear plot (Figure a) revealed that the electrocatalytic process is a diffusion-controlled process.…”

“…The electrochemical activity is well interpreted through the electrochemical active surface area (ESCA), which is directly proportional to the double-layer capacitance. 24 The linear plot (Figure 8a) revealed that the electrocatalytic process is a diffusioncontrolled process. The current is due to the facile electron flow at the electrode/electrolyte interface.…”