Solutions for effective energy conversion and storage are needed for the shift from fossil fuel-based, CO2-intensive energy production to a future sustainable energy-based economy. This way green energy from renewable sources, such as solar or wind power, may later be re-electrified. One option is to use water electrolysis to transform energy from renewable sources into chemical energy in the form of hydrogen. Proton Exchange Membrane (PEM) electrolysis is a potent, cutting-edge technique that leverages rare iridium-based catalysts to boost the oxygen evolution reaction (OER) to solve this issue. Reducing the total density of iridium-based catalysts for the OER requires minimizing the usage of rare and valuable iridium, which will enhance the PEM process's sustainability and economics.Here we present an investigation aimed to further reduce the iridium usage for proton-exchange membrane (PEM) electrolysis. First, SnO2 nanofibers are produced utilizing a water-free alkoxide route. A wet-chemical method is then used to deposit nanoparticulate IrO(OH) x on the filaments. After subsequent oxidation at various temperatures, the final OER active catalyst is obtained.With the emphasis on reaching high activity, stability, and conductivity at the laboratory level, ultra-small interconnected IrO x /IrO2 nanoparticles anchored to electrospun SnO2 nanofibers (IrO x /IrO2@SnO2) and associated percolation pathways are investigated. The utilization of transmission electron microscopy (TEM) in scanning mode (STEM) before and after electrocatalytic reactions provides insights into the oxidation and crystallization state of iridium oxide nanoparticles dependent on temperature and upon catalytic use. This enables an understanding of further possible reduction of iridium content by optimizing synthesis parameters. The data indicate that the optimal iridium utilization is achieved at 375°C oxidation temperature, with the highest resulting conductivity and electrochemical activity. Furthermore, TEM data reveal initiation of crystallization of IrO2 in the temperature window between 365 and 375°C. The pivotal role of conductivity in electron transport to active sites is underscored by cyclic voltammetry (CVA) measurements, which provide further insight regarding performance and stability with a view on future PEM electrolysis applications. These findings not only enhance our fundamental understanding but also offer practical strategies for advancing cost-effective and efficient electrolysis technologies.
Read full abstract7-days of FREE Audio papers, translation & more with Prime
7-days of FREE Prime access