As the smallest entities in catalysts, single-atom catalysts (SACs) exhibit superior atomic efficiency, advanced activity, and high selectivity. However, their practical applications are inhibited due to their high preparation costs. Here, we developed a novel cobalt–carbon-based SAC derived from the mild pyrolysis of spent coffee grounds soaked in Co (Co-CGBC), in which cobalt atoms atomically disperse and coordinate with the N and S atoms in the carbon substance, as identified by X-ray absorption fine structure (XAFS) spectroscopy combined w...