NiO/MoO2/MoO3 prepared by normal pulse voltammetry as cathode catalysts to investigate the properties of microbial electrolysis cells

Abstract

AbstractBACKGROUNDA microbial electrolysis cell (MEC) is a bio‐hydrogen production device that uses electrochemically active bacteria on the anode combined with applied voltage to break down organic matter. However, the effects of element content on cathode reduction and cathode catalysts on bioanode activity remain unknown.RESULTSMEC cathodes with different content of Na2MoO4·2H2O (i.e. 0 g L−1 (Ni), 12.5 g L−1 (Ni–Mo 1), 25 g L−1 (Ni–Mo 2) and 37.5 g L−1 (Ni–Mo 3)) were fabricated by normal pulse voltammetry to evaluate the cathode performance. Nanoparticles of Ni electrode are crystalline NiO on the carbon fiber surface. Compared with the Ni electrode, the catalysts of Ni–Mo electrodes are composed of smaller crystalline NiO and amorphous Mo oxides. The results of electrochemical analysis confirmed that Ni–Mo 1 exhibited low exchange transfer resistance (148.72 Ω), high electrochemically active surface area and strong conductivity, resulting in optimal electrocatalysis performance. The newly fabricated electrodes are applied as cathodes in single‐chamber MEC reactors and inoculated with activated sludge from a municipal wastewater treatment plant. High peak current density determined using cyclic voltammetry of the bioanode indicated the strong electrochemical activity of electroactive bacteria in the bioanode of Ni–Mo 1. This is because the low resistance in the MECs could accelerate electron transfer and boost electrochemical reaction.CONCLUSIONSThe performance of cathodes with different Ni and Mo content in terms of electrochemical activity was evaluated. Consequently, the optimal cathode electrode in MECs was Ni–Mo 1. The obtained results reveal that the cathode affects the bioanode activity in MECs. © 2023 Society of Chemical Industry (SCI).