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

Area of Science:

• Materials Science
• Biotechnology
• Electrochemistry

Background:

• Yeast-derived biochar is a promising material for catalysis.
• Developing efficient electrocatalysts for hydrogen evolution and nitrate reduction is crucial.
• Previous methods using yeast for transition metal phosphides (TMPs) biochar have limitations.

Purpose of the Study:

• To synthesize and characterize a novel cobalt phosphide (CoP)-loaded biochar using a phosphorus-accumulating yeast mutant.
• To evaluate the electrocatalytic performance of the CoP-loaded biochar for hydrogen evolution and nitrate reduction.
• To investigate the structural properties of the biochar and their correlation with catalytic activity.

Main Methods:

• Cultivation of a phosphorus-accumulating mutant strain of *Saccharomyces cerevisiae*.
• Tetrahydrofuran (THF) treatment of the yeast biomass followed by pyrolysis.
• Characterization of the resulting biochar using scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
• Electrochemical evaluation for hydrogen evolution reaction (HER) and nitrate reduction reaction (NRR).

Main Results:

• Formation of CoP-loaded biochar (CoP@P-yeast) with TMPs primarily on the biochar surface.
• CoP@P-yeast demonstrated an overpotential of -192 mV at 10 mA cm^-2 for HER.
• Achieved a high ammonia production rate of 33 mg-NH₃ h^-1 mg-catalyst^-1 in NRR, surpassing platinum on graphitized carbon.
• Observed that large TMP crystals on the surface may prevent catalytic deterioration.

Conclusions:

• A phosphorus-accumulating yeast mutant is an effective precursor for producing highly active TMP biochar.
• The CoP@P-yeast catalyst exhibits excellent performance in both hydrogen evolution and nitrate reduction.
• The surface localization of TMPs contributes to the catalyst's stability and efficiency.