Highly active and stable IrO2 and IrO2-Ta2O5 catalysts for oxygen evolution reaction

The oxygen evolution reaction (OER) performance of nanosized iridium oxide-nanosheet-like based electrocatalysts synthesized by a modified Adams method is reported in this work. Cysteamine hydrochloride was introduced during the synthesis of IrO2 to induce the evo-lution of nanosheet-like morphology from spherical particles. The IrO2 crystallinity prepared by the modified Adams method was greatly affected by calcination temperature. When the temperature increases to 400 & DEG;C, the resulted iridium oxide transitions from pseudo -amorphous to crystal rutile type. Electrochemical evaluation results show that the IrO2 synthesized at 400 & DEG;C performs the best in terms of enhanced mass activity (1.104 A mg-1@1.6 V) and lower overpotential (315 mV@10 mA cm-2) as compared with the counterparts prepared at other temperatures. Ta2O5 with different molar ratios of Ir/Ta was incorporated to further improve the stability of iridium oxide and to reduce its usage as anode catalyst. Ultrathin IrO2-Ta2O5 nanosheets with optimized Ir/Ta = 7: 3 M ratio outperform the commercial IrO2 benchmark in terms of OER activity and stability. The overpotential of IrO2-Ta2O5(7: 3) is at 326 mV@10 mA cm-2, and its mass activity is as high as 0.9 A mg-1@1.6 V. Chronopotentiometry and chronoamperometry tests verify its excellent durability.& COPY; 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This work reports the oxygen evolution reaction (OER) performance of nanosized iridium oxide-nanosheet-like electrocatalysts synthesized by a modified Adams method. By introducing cysteamine hydrochloride during the synthesis process, the morphology of the iridium oxide transformed from spherical particles to nanosheet-like structure. The electrochemical evaluation results show that the IrO2 synthesized at 400°C exhibits the best performance in terms of enhanced mass activity and lower overpotential compared to counterparts prepared at other temperatures. Ta2O5 was further incorporated to improve the stability of iridium oxide, and the optimized IrO2-Ta2O5 nanosheets with a 7:3 M ratio of Ir/Ta outperform the commercial IrO2 benchmark in terms of OER activity and stability.