Electronic Conductivity of Films of Electroflocculated 2 nm Iridium Oxide Nanoparticles

Abstract

The electronic conductivity of films of iridium oxide (IrO(x)) composed of ca. 2 nm nanoparticles (NPs) is strongly dependent on the film oxidation state. The Ir(IV)O(x) NPs can be electrochemically converted to several oxidation states, ranging from Ir(III) to Ir(V) oxides. The NP films exhibit a very high apparent conductivity, e.g., 10(-2) S cm(-1), when the NPs are in the oxidized +4/+5 state. When the film is fully reduced to its Ir(III) state, the apparent conductivity falls to 10(-6) S cm(-1).

Iridium Oxide Redox Gradient Material: Operando X-ray Absorption of Ir Gradient Oxidation States during IrOx Bipolar Electrochemistry

“…An estimation of the actual induced dipole in these conditions based on previous measurements 15 suggests that the external imposed 7 V creates a 0.7−1 V between IrO x borders. On the other hand, the expected dipole, simulated by COMSOL finite element calculations, yields 0.4 V even if a decrease of conductivity of the reduced part occurs (conductivity data of 1.1 × 10 −2 S/cm in the electrodeposited IrO x to 1.5 × 10 −6 S/cm for the reduced species 27 ).…”

“…A finite element simulation was performed using COMSOL Multiphysics software in its electrostatic module, which was then used to estimate the expected dipoles induced in the 2 mm stripes for each potential applied. In addition, a case where both the original IrO x and the reduced phase were present was considered (using reported conductivity values of 1.1 × 10 −2 S/cm for IrO x as deposited and 1.5 × 10 −6 S/cm for the reduced IrO x , 27 presumably the Ir(III) state). The geometric cell constrains were equal to those of the cell described above.…”

The Stability Challenges of Oxygen Evolving Catalysts: Towards a Common Fundamental Understanding and Mitigation of Catalyst Degradation

“…[74] On the other hand, supports with conductivities as low as 0.1 Scm À1 have been used in OER electrocatalysis [75] and can be taken as am inimum conductivity required for support structures of OER catalysts.C onductivities of IrO 2 vary between 2.7 10 4 Scm À1 for thin IrO 2 films [76] and 10 À2 Scm À1 for electroflocculated and unsupported IrO 2 nanoparticle films. [77] Common catalyst supports are based on titanium and its oxides as well as conductive transparent oxides such as antimony-or fluorine-doped tin oxide and tin-doped indium oxide (ATO,F TO,and ITO, respectively). [35e, 53,78] Angewandte Chemie Reviews Oh et al have reported the synthesis of mesoporous and conductive transparent oxides.O ft he investigated oxides, mesoporous ATO( meso-ATO) showed the highest conductivity (0.29 Scm À1 )a nd ah ighly stable cyclability (> 10 000 cycles).…”

Electrochemical Effects of Depositing Iridium Oxide Nanoparticles onto Conductive Woven and Nonwoven Flexible Substrates

“…This property allows a wide range of electrolyte solutions to be used in capacitor fabrication. Moreover, the NPs can be easily electrodeposited onto materials at a constant potential over varying periods of time to obtain any specified degree of deposition …”

“…Moreover, the NPs can be easily electrodeposited onto materials at a constant potential over varying periods of time to obtain any specified degree of deposition. 43 For wearable energy storage device fabrication, research is not entirely focused on achieving higher energy/power densities and cycle stability but also focused on material nontoxicity and environmental benignity. 44 Therefore, it is important to study aqueous solutions/gels as electrolytes because they are safe and cost-effective alternatives to volatile, less conductive organic electrolytes.…”