Tailoring Porous N‐Doped Carbon Nanospheres for 3D Bottom‐Up Electrode Design: A Versatile Synthesis Toolbox for Particle Size Independent Pore Size Control

The rational design of carbon-based electrode materials plays an important role in improving the electrochemical properties of both, energy storage and energy conversion electrodes and devices. For most applications, well-defined and easily processable porous carbon-based electrode materials with controlled particle morphology (ideally spherical), particle size, and intraparticle pore size are desired. Here, a hard-templating synthesis toolbox is reported for highly-monodisperse meso- and macroporous N-doped carbon nanospheres (MPNCs) as a versatile material platform for the 3D bottom-up design of porous electrodes. With this approach, it is possible to change the MPNC pore size without affecting the particle size. By changing the template size, the pore size is adjusted between 15 and 99 nm while maintaining a particle size ≈300 nm. MPNCs are further used in electrochemical double-layer capacitors (EDLCs) as model application to demonstrate pore size effects on the performance independently from particle size effects, resulting in increasing specific capacitances for decreasing pores sizes, which correlates well with the surface area of the MPNCs and mass transport phenomena in the electrode. In conclusion, the toolbox allows to control intraparticulate porosities while keeping interparticulate properties constant, essential parameters to enable a true bottom-up 3D electrode design.