Ex-Situ Electrochemical Characterization of IrO2 Synthesized by a Modified Adams Fusion Method for the Oxygen Evolution Reaction

Abstract

The development of highly stable and active electrocatalysts for the oxygen evolution reaction (OER) has attracted significant research interest. IrO2 is known to show good stability during the OER however it is not known to be the most active. Thus, significant research has been dedicated to enhance the activity of IrO2 toward the OER. In this study, IrO2 catalysts were synthesized using a modified Adams fusion method. The Adams fusion method is simple and is shown to directly produce nano-sized metal oxides. The effect of the Ir precursor salt to the NaNO3 ratio and the fusion temperature on the OER activity of the synthesized IrO2 electrocatalysts, was investigated. The OER activity and durability of the IrO2 electrocatalysts were evaluated ex-situ via cyclic voltammetry (CV), chronopotentiometry (CP), electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV). Physical properties of the IrO2 electrocatalysts were evaluated via X-ray diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), differential thermal analysis (DTA), and energy dispersive spectroscopy (EDS). The results show that the addition of excess NaNO3 during the modified Adams fusion reaction is not a requirement and that higher synthesis temperatures results in IrO2 electrocatalysts with larger particle sizes and reduced electrocatalytic activity.

IrO2 Surface Complexions Identified through Machine Learning and Surface Investigations

“…The theoretical predictions are supported by surface investigations of IrO 2 single crystals, which exhibit (101) facets rather than the more common low-energy (110) orientation of rutile [23,24]. Characterization by low-energy electron diffraction (LEED), scanning-tunneling microscopy (STM), and x-ray photoelectron spectroscopy (XPS) confirms the properties of the predicted metal-rich complexions, explaining why IrO 2 nanoparticles often expose (101) facets [25][26][27][28][29][30][31].…”

“…[22,23] Characterization by low-energy electron diffraction (LEED), scanning-tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) confirms the properties of the predicted metal-rich complexions, explaining why IrO2 nanoparticles often expose (101) facets. [24][25][26][27][28][29][30] Our investigation starts with the creation of a reference database of DFT structures to train the non-parametric GAP potential. GAPs decompose the total energy of a system into a sum of atomic energies that depend on the local chemical environment.…”

Porous SnO2 nanostructure with a high specific surface area for improved electrochemical performance

“…Typically, porous metal oxides with high specic surface areas have been prepared using the Adams fusion method due to their various merits such as facile preparation procedure, low reaction temperature, short reaction time, and high yield. [22][23][24][25][26] Thus, in this study, the SnO 2 sample prepared using the Adams fusion method, with high specic surface areas and particular pore structures showed improved LIB performance compared to a commercial SnO 2 because of the enhanced stability caused by relieved volumetric expansion during cycling.…”

Study of lifetime of Platinum Modified Metal Oxides Electrodes

“…The cracks observed on the electrodes surface occur during the cooling of the deposit due to the thermal shock to which these deposits are subjected during their removal from the oven. On the iridium oxide electrode, the peaks observed at 0.7 V and 1 V /SCE potentials on the voltammetric curve characterize the electrochemical behavior of the IrO2 electrode (Felix et al, 2019;Kariman et al, 2019). These peaks observed at these potentials correspond to the redox transitions of Ir(III) / Ir(IV) and Ir(IV) / Ir(VI) (Ouattara et al, 2009;Kapałka et al, 2009).…”