Zirconia/Porous Carbon Derived from UiO-66 as an Efficient Electrocatalyst Carrier for Oxygen Reduction Reactions

The development of high-performance, low-platinum (Pt)-loading catalysts for the oxygen reduction reaction (ORR) remains a critical challenge in proton exchange membrane fuel cells. Zirconium dioxide-carbon composite materials are prepared using the Zr-based metal-organic framework UiO-66 as a precursor. The support structure is modulated by controlling the pyrolysis conditions (700 °C, 800 °C, and 900 °C). Platinum nanoparticles are deposited onto the ZrO 2 -carbon composite framework using ethylene glycol as the reducing agent, yielding low-Pt-content Pt/U-X catalysts (X = 700, 800, 900). The findings demonstrate that the Pt/U-X catalysts exhibit superior electrocatalytic activity compared with commercial Pt/C catalysts. Pt/U-800 displays the highest mass activity (796.9 mA mg Pt −1 ), which is 3.64 times higher than commercial Pt/C (219.2 mA mg Pt −1 ). Furthermore, Pt/U-800 achieves 1250 mA cm −2 at 0.6 V and reaches a peak power density of 1820 mW cm −2 in fuel cell tests. The one-step composite of ZrO 2 and carbon, formed through the pyrolysis of UiO-66, facilitates an interfacial structure between ZrO 2 and Pt, optimizing the hierarchical pore structure of the support, and providing a promising, cost-effective alternative to traditional Pt/C catalysts for fuel cell cathod. Graphical ZrO 2 –carbon composite supports were derived from UiO-66 (a Zr-based metal–organic framework, MOF) by pyrolysis. Pyrolysis temperature regulates graphitization and oxygen vacancies (O v ), strengthening Pt–support interactions. The optimized Pt/U-800 catalyst forms a Pt δ+ –O v –Zr 3+ interface and exhibits enhanced oxygen reduction reaction (ORR) activity with higher half-wave potential (E 1/2 ) and mass activity (MA) than commercial Pt/C.