Pore Size Independent Particle Size Control of Mesoporous N-doped Carbon Nanospheres for 3D Bottom-Up Electrode Design

Abstract

The rational design of electrodes is crucial for improving electrochemical energy storage and conversion devices. High-performance devices require porous carbon electrodes with controlled intraparticle properties — such as morphology, size, porosity, elemental composition, and graphitic microstructure — and interparticle features like electrode-level porosity, percolation pathways, and tortuosity, that influence mass transport. Here, mesoporous N-doped carbon (MPNC) nanospheres with independently tunable particle size at a fixed pore size is reported. Extending the previously established synthesis toolbox, independent control over particle and pore sizes is demonstrated. Using a 9 nm SiO2 hard template, particle sizes between 50 and 300 nm is adjusted while maintaining comparable physicochemical properties. These MPNC nanospheres are evaluated as supercapacitor electrodes in coin cells using 1.0 m LiPF6 in EC/DEC as electrolyte. The highest specific capacitance — 67 F g−1 at 0.1 A g−1 — is obtained with the largest particles, attributed to reduced tortuosity and improved electrode percolation. As all samples exhibited similar surface areas (≈950 m2 g−1), performance differences highlight particle size-dependent diffusion limitations. This study establishes a bottom-up approach for engineering electrode architectures, enabling independent control of pore and particle sizes of MPNC nanospheres and providing a platform to systematically investigate their effects on electrochemical performance.