Solid-phase microbial fuel cells (SMFCs) are promising clean energy that can convert soil/sediment organic matter into usable electricity. However, the practical application of SMFCs require to increase output power, improve energy conversion efficiency, and reduce electrode material costs. In this study, three porous biomass materials, namely, corn stems (CSs), commercial bread (CB), and loofah sponges (LSs), were studied to construct three-dimensional (3D) electrode materials with different pores for improving the performance of SMFCs through a simple carbonization process. The material structure properties of the 3D electrode were evaluated by scanning electron microscopy, X-ray photon spectroscopy, impedance, and cyclic voltammetry. Results showed that CS had the highest effective electrochemical specific surface area and the lowest charge-transfer resistance. The power densities of SMFCs with CSs, CB, and LSs were 66, 47, and 16 mW/m(2), respectively, while the power density of SMFCs with carbon felt was only 13 mW/m(2). The pore sizes of CSs were smaller than that of another 3D electrode, which was conducive to improving the electron-transfer rate for increasing the substrate mass transfer rate and biocompatibility in SMFCs. CSs were also an excellent and cost-effective material for establishing 3D electrodes to improve the performance of SMFCs.