Exfoliated molybdenum di-sulfide (MoS₂) electrode for hydrogen production in microbial electrolysis cell

The most widely reported catalyst in microbial electrochemical cells (MEC) cathodes is platinum (Pt). The disadvantages of Pt include its high cost and sensitivity to various molecules. In this research an exfoliated molybdenum di-sulfide (MoS₂-EF) catalyst was synthesized. The size of the obtained particles was 200 ± 50 nm, 50-fold smaller than the pristine MoS₂ catalyst. The MoS₂-EF Raman spectrum displays the E¹_2g and A_1g peaks at 373 cm^-1 and 399 cm^-1. Electrochemical characterization by linear sweep voltammetry (LSV) of a rotating disc electrode RDE showed that the current density of Pt in 0.5 M H₂SO₄ was 3.3 times higher than MoS₂-EF. However, in phosphate buffer (pH-7) electrolyte this ratio diminished to 1.9. The polarization curve of Pt, MoS₂-EF and the pristine MoS₂ electrodes, at -1.3 V in MEC configuration in abiotic conditions exhibit current densities of 17.46, 12.67 and 3.09 mA cm^-2, respectively. Hydrogen evolution rates in the same MEC with a Geobacter sulfurreducens anode and Pt, MoS₂-EF and the pristine MoS₂ cathodes were 0.106, 0.133 and 0.083 m³ d^-1 m^-3, respectively. The results in this study show that MoS₂-EF led to highly purified hydrogen and that this catalyst can serve as an electrochemical active and cost-effective alternative to Pt.