A Comparison of Pd/C, Perovskite, and Ni-Fe Hexacyanoferrate Bifunctional Oxygen Catalysts, at Different Loadings and Catalyst Layer Thicknesses on an Oxygen Gas Diffusion Electrode

Abstract

Air electrode development is one of the most challenging steps in the design of lightweight and efficient metal-air batteries and fuel cells. The best performing oxygen catalysts often contain precious metals at a high manufacturing cost. In this paper, two low-cost catalysts for the oxygen reduction (ORR) and evolution reactions (OER), based on LSFCO perovskite and Ni-Fe hexacyanoferrate, were compared with a precious metal palladium catalyst on carbon (Pd/C). LSFCO/C showed the best all-round performance as a single bifunctional catalyst but Pd/C had the strongest ORR activity. Ni-Fe hexacyanoferrate is straightforward to manufacture in industrial quantities, and is more active for the OER than palladium and LSFCO perovskite at small loadings < 5 mg cm −2 . By mixing a small loading of Pd/C with Ni-Fe hexacyanoferrate, lower overpotentials for both the ORR and OER can be reached, with the difference in potential between the two reactions being only 0.62 V at a current density of 20 mA cm −2 . The effect of catalyst loading of each catalyst on the gas-diffusion electrode was studied, and rotating disk voltammetry was used to study the catalytic behavior of the Ni-Fe hexacyanoferrate catalyst.

Effect of 1-octanethiol as an electrolyte additive on the performance of the iron-air battery electrodes

“…2). As previously shown for this catalyst [24], the air electrode in the 6 mol dm −3 KOH solution showed a remarkably stable charge/discharge behaviour even at relatively high current densities (> 300 mA cm −2 ). The addition of 1-octanethiol increased the oxygen reduction overpotential at the electrode for both the 0.01 and 0.1 mol dm −3 concentrations of octanethiol.…”

“…The air electrodes were composed of three layers: a hydrophobic layer, catalyst layer, and current collector. They were prepared according to a method described in reference [24]. For the preparation of the hydrophobic layer, 5 g of carbon paste A (60% C, 40% PTFE) was deposited on a 5 × 2 cm 2 carbon cloth and hot-pressed at 140°C and 25 kN for 10 min, then heated in a furnace for curing at 380°C for 5 min to evaporate the remaining PTFE solvent.…”

Role of Electrode Thickness in NiFe Nanogranular Films for Oxygen Evolution Reaction

“…For MnO/Si 34 and LaSrMnO films, 35 a thickness analysis in the 1−27 nm range revealed the best OER efficiency for 4 nm thick films, while for NiFe hexacyanoferrate (0.5−10 mg/cm 2 range) a 5 mg/cm 2 has been identified as the ideal concentration. 36 For electrodeposited transition metal oxides, 37 the TOFs reported in the 0.1−100 μg/cm 2 density range show a high dependence on the oxide type, going from 10 s −1 for CoFeO to 0.001 s −1 for MnO. Moreover, NiFe oxyhydroxides (1.5−20 μg/cm 2 loading range) 38 and NiFeO (0.3−3.8 nmol/cm 2 ) 39 present a substrate-dependent TOF/loading behavior since the substrate is affecting the catalytic particle dispersion in the electrode.…”

Electrocatalysis of Oxygen on Bifunctional Nickel‐Cobaltite Spinel

“…However, this kind of batteries requires very efficient and durable bifunctional electrocatalysts to accelerate the kinetics of oxygen reduction reaction (ORR), taking place during the discharge, and oxygen evolution reaction (OER), occurring during charging of the battery. [8][9][10][11][12] Nowadays, the state-of-the-art catalysts are Pt-based nanoparticles for the ORR and IrO 2 for the OER. [13][14][15] However, the high cost of these electrocatalysts makes these materials unattractive.…”

“…These make them particularly interesting for applications in electrical‐energy storage systems for coupling intermittent renewable energy sources into smart energy grids. However, this kind of batteries requires very efficient and durable bifunctional electrocatalysts to accelerate the kinetics of oxygen reduction reaction (ORR), taking place during the discharge, and oxygen evolution reaction (OER), occurring during charging of the battery . Nowadays, the state‐of‐the‐art catalysts are Pt‐based nanoparticles for the ORR and IrO 2 for the OER .…”