UCLA

Proton-exchange-membrane fuel cells (PEMFCs) directly convert chemical energy into electricity with water as the only byproduct, providing a promising pathway toward a zero-emission future. Their commercial success has been demonstrated in light-duty vehicles (LDVs) exemplified by the Toyota Mirai. Compared with battery electric vehicles (BEVs), fuel cell electric vehicles (FCEVs) offer distinct advantages for heavy-duty vehicles (HDVs), including shorter refueling time, higher payload capacity, and reduced weight penalty. However, the harsh operating conditions and prolonged service life of HDVs impose stringent requirements on PEMFC durability, while the increasing demand for Pt catalyst calls for reduced Pt utilization and scalable manufacturing. Therefore, developing highly durable, cost-effective, and industrially scalable Pt-based electrocatalysts is critical for the widespread commercialization of PEMFCs in heavy-duty transportation. Chapter 2 presents a graphene-nanopocket protected Pt nanoparticle (Pt@Gnp) that enhances durability by suppressing Pt dissolution, particle coalescence, and ionomer poisoning during accelerated-stress-tests (ASTs). The resulting fuel cell exhibits only 1.1% rated power loss after 90,000 AST cycles, corresponding to a projected lifetime exceeding 200,000 h, more than seven times the U.S. Department of Energy (DOE) ultimate target for heavy-duty applications (30,000 h). Chapter 3 introduces a unique design of Pt nanoparticles embedded with cerium oxide clusters (CeOx@Pt), in which strong CeOx-Pt interactions suppress Pt dissolution, migration, and particle growth. The catalyst satisfies the DOE heavy-duty end-of-life (EOL) performance target of 1.07 A/cm2 at 0.7 V after 90,000 AST cycles at a low total-PGM-loading of approximately 0.1 mgPGM/cm2, reducing Pt cost by 70% relative to the DOE Million-Mile Fuel Cell Truck (M2FCT) Consortium target. Chapter 4 develops a laser ablation-based synthesis strategy for Pt nanocatalysts that increases production throughput by 10-folds compared with conventional wet-chemical synthesis. The rapid heating and cooling inherent to laser ablation also create metastable nanotwinned structures that enhance catalyst durability during fuel cell operation. Overall, the work presented in this dissertation demonstrates complementary catalyst design and synthesis strategies that simultaneously improve durability, reduce Pt utilization, and enable scalable catalyst manufacturing. These advances provide practical pathways toward the commercialization of PEMFCs for heavy-duty transportation and contribute to the broader transition toward sustainable, zero-emission transportation.