Promoting Energy Sustainability through Fundamental Study of Precious Metal Catalysts for Fuel Cells and Electrolyzers

Clean and efficient energy technologies are in high demand to resolve the issues related to limited fossil fuels and the climate crisis. Recently, electrochemical conversion devices, such as fuel cells and electrolyzers, demonstrate a viable option for a sustainable energy system. Electrolyzers can generate green hydrogen through water electrolysis, which can then be used in fuel cells to directly convert chemical energy to electricity. However, there are still technical barriers that need to be addressed before reaching full commercialization in these emerging technologies. For fuel cells, especially in heavy-duty vehicle applications, durability is a critical concern to be competitive with internal combustion engines. One of the key degradation losses in fuel cells comes from the catalyst layer made of platinum nanoparticles dispersed on carbon support (Pt/C). Here, a fundamental study was conducted to investigate the degradation mechanism of Pt/C using accelerated durability testing protocols in acidic and alkaline media. It was found that the generation of carboxyl functional groups due to carbon corrosion in acid poisons the Pt active sites during oxygen reduction reaction (ORR). In alkaline, carbon dissolution happens that triggers the formation of large Pt agglomerates. For electrolyzers, hydrogen generation relies on an expensive and scarce iridium metal as a catalyst for the oxygen evolution reaction (OER). To lower the cost of this device, alternative materials are developed to reduce the iridium (Ir) loading. We proposed to enhance Ir utilization by alloying with cobalt (Co), being a less expensive and more available metal. Surfactant-assisted Adam’s fusion synthesis technique was developed as a scalable method to produce IrCo catalysts. The synthesized material outperforms commercial Ir baseline catalysts, in both acidic and alkaline media. In addition, the effects of the Ir/Co molar ratio, the use of surfactant, and acid etching were investigated to enhance OER performance. In this dissertation, the catalytic performance and degradation mechanisms of precious metals for ORR and OER in both acid and alkaline media were successfully studied using a half-cell electrochemical set-up and physicochemical characterization tools. The new findings provide insights into developing more efficient and durable fuel cells and electrolyzers to promote energy sustainability toward a decarbonized society