M.G. Chourashiya

Solution combustion synthesis of highly dispersible and dispersed iridium oxide as an anode catalyst in PEM water electrolysis

Iridium based materials are state-of-the-art anode catalysts for polymer electrolyte membrane (PEM) water electrolysis thanks to their unmatched stability and performance in the acidic environment of common PEMs like Nafion®. However, their cost restricts their use in large-scale operations. To improve their utilization, identifying a synthesis method of nano-structured iridium oxide with a high active surface area, possibly in a supported form, is of great importance. For this aim, we developed a one-step and cost-effective solution combustion synthesis (SCS) method to prepare nano-structured IrO2 and IrO2-based materials suitable for PEM electrolysis. Among various materials prepared, the iridium oxide incorporated and dispersed in amorphous alumina showed a high surface area (131 m2 g−1) and the current density of 1.78 A cm−2 at 1.8 V which is comparable to the performance of the state-of-the-art commercial membrane electrode assembly (MEA) made of IrRuOx (1.8 A cm−2 at 1.8 V) under PEM water electrolysis. Importantly, the dispersion of the material in the catalyst ink used for the preparation of the MEA was significantly superior compared to that of commercial IrO2 nanoparticles and the amount of the precious metal in the catalyst made by SCS could be reduced by 45 wt% compared to that in the commercial MEA.

SYNTHESIS OF HIGHLY ACTIVE Mg-BASED HYDRIDES USING HYDRIDING COMBUSTION SYNTHESIS AND NbF5 ADDITIVES

Superiority of the hydriding combustion (HC) technique over conventional metallurgical approach to the synthesis of cost-effective Mg based hydrides, which show promise as hydrogen storage materials, is well known. In the present research, we report further improvements in HC prepared Mg-based materials, achieved by optimizing the preparative parameters of HC and by catalytic addition. Mg90-Ni60-C40 composites prepared using optimized processing parameters were ball-milled with NbF5 (10 h) and characterized for their micro-structural and hydriding properties. The ball-milled/catalyzed powder showed decreased crystallinity with CNTs on its surfaces. Surface area of the ball-milled powder decreased to almost half of the as-HC powder, while TG analysis revealed a four-fold decrease in the desorption temperature of the milled powder compared to that of the as-HC prepared powder. Activated samples achieved the maximum absorption/desorption limits (5.3 wt.%) at as low as 100°C, underlining the possibility of the use of these materials in portable hydrogen storage devices.