Development of nanoparticle catalysts with the green synthesis method and their application in PEM electrolysis cells

In this study, a green synthesis approach was adopted as an environmentally friendly, economical, and sustainable method for proton exchange membrane (PEM) electrolysis cells that convert electrical energy into chemical energy. In this context, a reducing agent with low environmental impact and cost was obtained using pistachio leaf extract, a biological waste, and NiO, LaO, and CeO2 metal oxide nanoparticles were synthesized using this material. These synthesized metal oxide nanoparticles, along with high electrochemical activity IrO2, were transformed into IrO2-NiO, IrO2-CeO2, and IrO2-LaO composite catalysts using the Adams fusion method and tested as anode catalysts in PEM electrolysis cells. Performance evaluations were conducted using polarization measurements at a constant liquid flow rate and a temperature range of 20–70°C. The results showed that the IrO2-NiO catalyst exhibited the best electrochemical performance by achieving the lowest cell voltage and highest current density values. The IrO2-CeO2 catalyst produced high power density at high voltages. Although CeO2's activity increased at high potentials due to its ability to generate oxygen vacancies, its low conductivity limited the reaction kinetics. The IrO2-LaO catalyst, on the other hand, exhibited moderate performance; despite its low electrical conductivity, it exhibited better activity than CeO2 but lower activity than NiO due to the chemical interaction between LaO and IrO2. The structural, morphological, and surface properties of all catalysts were characterized in detail by XRD, TEM, and XPS analyses. The electrochemical activity and power density performances of different metal oxide-supported IrO2 catalysts were compared, and the NiO-supported IrO2 catalyst was determined to be the most suitable anode catalyst composition for PEM electrolysis cells.