Hierarchical Porous Pt/ZrO2 Nanoframework for Efficient Oxygen Reduction Reaction

Rational regulation of the three-dimensional (3D) intrinsic configuration of nanocatalysts is essential for the complex three-phase interfacial mass transfer process in the oxygen reduction reaction (ORR) and proton membrane exchange membrane fuel cells (PEMFCs). In this work, we developed a highly efficient 3D hierarchical porous ORR catalytic system by introducing stable and multiaperture zirconia (ZrO2) and conductive N-doped carbon (NC) into a Pt-based catalyst. We found that the constructed Pt-ZrO2 interface greatly promotes the activation of O2 by modulating the electronic state of Pt nanoparticles. The hierarchical porous structure of a NC-encapsulated nanoframework compensates for the system conductivity, promoting the mass diffusion and the electron transfer of catalytic species, thereby enhancing the ORR activity and stability. This developed hierarchical porous ORR catalytic system exhibits a good mass activity/specific activity of 1.26 A mgPt-1/ 1.44 mA cm-2, which is 4.5/5.8 times higher than that of commercial Pt/C. Moreover, it exhibits negligible activity decay and morphological stability after 30 K potential cycling. Our findings of integrating hierarchical porous systems to simultaneously optimize the geometric and electric structure of Pt-based catalysts should finally boost their development in practical PEMFCs.

Automated summary

In this study, a highly efficient 3D hierarchical porous oxygen reduction reaction (ORR) catalytic system was developed by incorporating stable and multiaperture zirconia (ZrO2) and conductive N-doped carbon (NC) into a Pt-based catalyst. The Pt-ZrO2 interface greatly enhances the activation of O2, while the hierarchical porous structure of a NC-encapsulated nanoframework promotes mass diffusion and electron transfer, leading to improved ORR activity and stability. This catalytic system exhibits significantly higher mass activity/specific activity than commercial Pt/C, and shows negligible activity decay and morphological stability after long-term cycling. The integration of hierarchical porous systems for optimizing the geometric and electric structure of Pt-based catalysts has great potential for practical proton exchange membrane fuel cells (PEMFCs).