Cobalt phosphide-loaded biochar synthesis using phosphate-accumulating yeast and its application as an electrocatalyst

A phosphorus (P)-accumulating mutant strain of <i>Saccharomyces cerevisiae</i> is used as a precursor for transition metal phosphides (TMPs) biochar. Tetrahydrofuran treatment of the P-accumulating yeast coupled with pyrolysis resulted in the formation of CoP-loaded biochar (CoP@P-yeast) unlike previously reported Co₂P-loaded biochar using dry baker's yeast. The CoP@P-yeast exhibited the electrocatalytic activity for the hydrogen evolution with an overpotential of -192 mV at 10 mA cm^-2. Furthermore, the CoP@P-yeast showed the highest ammonia production rate of 33 mg-NH₃ h^-1 mg-catalyst^-1 in nitrate reduction reaction, as well as much higher than that with platinum on graphitized carbon. Scanning electron microscopy and transmission electron microscopy observations revealed that relatively large TMP crystals mainly located at the biochar surface, which may be beneficial to avoid catalytic deterioration during the nitrate reduction reaction. This study demonstrates that P-accumulating mutant strain of yeast is a suitable precursor to improve the activity of the resulting TMP biochar.