Microbial electrochemical technologies (MET), among others, facilitate sustainable CO₂ conversion into chemicals at ambient temperature and neutral pH. Reactors used in MET, called bioelectrochemical systems (BES), come in different types; bed electrodes are prominent; however, they lack reproducible, geometrically defined granular electrodes. Typical carbon granules are irregular, have wide size distributions, and poorly defined electrochemical properties, which limit their engineering applications. This study introduces sphere-like granular biochar (GB) cathodes, produced by pyrolyzing beechwood spheres at 850°C (GB850). GB850 electrodes were modified and characterized on a single-granule basis. The hydrogen evolution reaction (HER) at neutral pH models abiotic cathodic reactions, reflecting its important role as an intermediate in CO₂-reducing BES. To improve electrocatalytic activity, GB850 was modified with nickel-molybdenum (GB850-NiMo), and the uniform electrodeposition was verified through structural and compositional analysis. GB850-NiMo exhibited an HER overpotential of only 106 ± 9 mV at −1 mA/cm², 85% lower than that of GB850. Its electrochemical double-layer capacitance (C_dl) increased fourfold after NiMo deposition, indicating a larger electrochemically active surface area. The apparent stability of GB850-NiMo highlights its potential to optimize bed electrodes in CO₂-reducing BES through controlled modifications. The highly defined geometry of sphere-like GB offers a valuable tool for future engineering.