Abstract
We have developed IrOx/M-SnO2 (M = Nb, Ta, and Sb) anode catalysts, IrOx nanoparticles uniformly dispersed on M-SnO2 supports with fused-aggregate structures, which make it possible to evolve oxygen efficiently, even with a reduced amount of noble metal (Ir) in proton exchange membrane water electrolysis. Polarization properties of IrOx/M-SnO2 catalysts for the oxygen evolution reaction (OER) were examined at 80 °C in both 0.1 M HClO4 solution (half cell) and a single cell with a Nafion® membrane (thickness = 50 μm). While all catalysts exhibited similar OER activities in the half cell, the cell potential (Ecell) of the single cell was found to decrease with the increasing apparent conductivities (σapp, catalyst) of these catalysts: an Ecell of 1.61 V (voltage efficiency of 92%) at 1 A cm−2 was achieved in a single cell by the use of an IrOx/Sb-SnO2 anode (highest σapp, catalyst) with a low Ir-metal loading of 0.11 mg cm−2 and Pt supported on graphitized carbon black (Pt/GCB) as the cathode with 0.35 mg cm−2 of Pt loading. In addition to the reduction of the ohmic loss in the anode catalyst layer, the increased electronic conductivity contributed to decreasing the OER overpotential due to the effective utilization of the IrOx nanocatalysts on the M-SnO2 supports, which is an essential factor in improving the performance with low noble metal loadings.
Highlights
Proton exchange membrane water electrolysis (PEMWE) is an attractive method to produce high purity hydrogen with high energy conversion efficiency, even at high current densities, together with easy maintenance, start-up, and shut-down [1,2,3,4]
We examined the polarization properties of a series of iridium oxide (IrOx) /M-SnO2 (M = Nb, Ta, and Sb) catalysts for the oxygen evolution reaction (OER) at 80 ◦ C in both 0.1 M HClO4 solution and a single cell with a Nafion® membrane
For a conventional catalyst employed as a reference, scanning electron microscopic (SEM) and transmission electron microscopic (TEM) images of
Summary
Proton exchange membrane water electrolysis (PEMWE) is an attractive method to produce high purity hydrogen with high energy conversion efficiency, even at high current densities, together with easy maintenance, start-up, and shut-down [1,2,3,4]. Such superlative characteristics make PEMWE suitable for leveling of the large fluctuations of renewable energy sources when used in combination with stationary fuel cells. It has been reported that the cell potentials (Ecell ) of PEMWE single cells with IrOx supported on SnO2 anodes reached values
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