N-doped macroporous carbon loading Mo2C as cathode electrocatalyst of hybrid neutral-alkaline microbial electrolysis cells for H2 generation

Abstract

Microbial electrolysis cells (MECs) show promise in energy-effective hydrogen (H2) production by harvesting electric energy from wastewater, while the implementation of such a desirable technique faces challenges of expensive cathodic catalysts and unfavorable neutral electrolyte for hydrogen evolution reaction (HER). This work presents a simple and cost-effective pyrolysis route to fabricate hybrid electrocatalysts of Mo2C loaded nitrogen-doped porous carbon (Mo2C/NC). The Mo2C/NC-800 catalyst delivers impressively high activity and durability in pH-varied electrolyte from alkali, neutral and acid, particularly in alkali condition (e.g. 1.0 M KOH) where the overpotential@10 mA cm−2 is only 138 mV which is comparable to the commercial Pt/C catalysts. A hybrid neutral-alkaline MEC is therefore developed that uses Mo2C/NC as the cathode catalyst for H2 production. The system requires an applied voltage of 1.0 V to achieve current density of ∼20.0 A m−2 at H2 generation rate of 170.5 L m−2 d−1. This MEC performance is considerably higher than that of the traditional symmetric neutral counterpart that requires an applied voltage of 1.0 V to achieve current density of ∼18.0 A m−2 at H2 generation rate of 159.4 L m−2 d−1 indicating promising potential of Mo2C/NC electrocatalyst to be applied in MEC device for H2 generation.