Strategy for predicting catalytic activity of catalysts with hierarchical nanostructures

Three-dimensional hierarchical nanostructures have been employed as electrodes of solid oxide fuel cells (SOFCs) to notably improve the catalytic performance. Hierarchical nanoscale porous electrodes face a trade-off: macroscale pores enhance mass transfer but reduce the number of active sites, while microscale pores increase the number of active sites at the cost of higher transport resistance. Careful design of these structures is crucial for balancing mass transfer and reaction dynamics. A three-dimensional multiphysics model is developed in this paper to examine the influence of different hierarchical geometrical nanostructures on catalytic performance. Additionally, the effects of different diffusion coefficients are also investigated in this study to present the changes in catalytic activity in diffusion, mixed, and reaction-controlled regimes. The model shows good alignment with the experimentally obtained data. An improved Thiele modulus is formulated to quantitatively evaluate the efficiencies of complex hierarchical nanostructures by considering the detailed characteristics of the main and secondary structures.