Using nickel-molybdenum cathode catalysts for efficient hydrogen gas production in microbial electrolysis cells

A low-cost cathode catalyst based on a NiMo alloy was examined here to replace noble metals for the hydrogen production in microbial electrolysis cells (MECs). Two NiMo catalysts were synthesized through either an electrochemical assisted (NiMo Elec) or a hydrothermal (NiMo Ht) approach. The NiMo Ht method enriched the electrocatalyst with Mo atoms compared to the NiMo Elec approach, producing a similar current density with a minimal overpotential of 50 mV compared to Pt. In MEC tests using the NiMo Ht catalyst, H2 was generated at a highest rate of 81 +/- 3 LH2/L-d (current density of 44.4 +/- 0.9 A/m2) at a cell voltage of-0.86 V, and a Coulombic efficiency of >97%. Modifying the closely stacked MEC design to include a reference electrode, and analysis of the electrode potentials using the electrode potential slope method, revealed a large contribution of the cathode resistance (5.3 +/- 0.5 m omega m2) compared to the anode (1.4 +/- 0.2 m omega m2) and ohmic resistance (0.83 m omega m2) for a total internal resistance of 7.6 +/- 0.5 m omega m2. The high performance of the NiMo Ht catalyst coupled with its low cost provides an economically viable approach to advance the generation of biohydrogen in MECs.

Automated summary

In this study, a low-cost cathode catalyst based on a NiMo alloy was examined for hydrogen production in microbial electrolysis cells (MECs) as an alternative to noble metals. Two NiMo catalysts were synthesized, one through an electrochemical assisted (NiMo Elec) approach and the other through a hydrothermal (NiMo Ht) approach. The NiMo Ht method showed a higher concentration of Mo atoms in the electrocatalyst compared to the NiMo Elec approach, resulting in a similar current density and minimal overpotential compared to Pt. The high performance and low cost of the NiMo Ht catalyst make it an economically viable approach for biohydrogen generation in MECs.