UCLA

Fuel cells are devices that can efficiently convert fuels into electricity without the limitation of the Carnot cycle. Particularly, hydrogen fuel cells have attracted enormous interest due to their high energy density, high efficiency, and low environmental impacts. The most widely adopted proton-exchange-membrane fuel cells (PEMFCs) use platinum (Pt) catalysts to drive both anode and cathode reactions. To date, the most significant roadblock to the broad dissemination of this green energy technology remains the acceleration and retention of the reaction rate of oxygen reduction reaction (ORR) at the cathode. Developing robust, active, and cost-effective ORR catalysts is the solution to this challenge.In my first work, I demonstrated a Cu doping strategy to enhance the intrinsic activity and durability of octahedral PtNi nanoparticles in the rotating-disk-electrode (RDE) setting. By a novel integration of simulations and growth tracking experiments, we uncover the beneficial role of increased surface Pt composition, which reduces the generation of surface vacancies and subsequent dissolution of sub-surface Cu and Ni atoms. Unlike the well-controlled RDE system, the critical role of mass transports in a practical membrane-electrode-assembly (MEA) system demands additional consideration in stability-enhancing strategies. Therefore, in my subsequent work, I recognized the critical challenge in MEA with ultralow Pt loading and designed a graphene-nanopocket-encaged platinum cobalt nanocatalyst with good electrochemical accessibility and exceptional durability in practical MEA testing. With the greatly improved rated power and durability, a 6.8 gram Pt loading is projected for a 90-kW PEMFC light-duty vehicle, approaching that used in a typical catalytic converter. Furthermore, I presented a unique design of ultrafine Pt nanocatalysts with embedded cobalt oxide clusters, which further improve the catalyst stability for durable PEMFCs. This endohedral-oxide design exploits the strong Pt/oxide interaction, which grants the catalyst its exceptional structural and chemical durability, without sacrificing activity. The developed nanocatalyst exhibits exceptional durability promising an outstanding projected lifetime of 15,000 hours.