Zero-Gap Microbial Electrolysis Flow Cells with 3D-Printed Electrodes for Efficient Wastewater Treatment and Hydrogen Production

Microbial electrolysis cells (MECs) offer a promising approach for simultaneous wastewater treatment and hydrogen (H2) production. However, their performance requires enhancement for practical deployment. In this study, a zero-gap microbial electrolysis flow cell (MEFC) was developed using 3D-printed electrodes aimed for efficient wastewater treatment and H2 production. Graphene oxide (GO)/MXene bioanodes and MXene/Pt cathodes were successfully fabricated via direct ink writing (DIW)-based 3D printing, enabling precise control of porosity and architecture. The 3D-printed porous electrodes provided a large surface area for substrate diffusion and gas transport, promoting microbial colonization, facilitating efficient electron transfer, and improving hydrogen evolution efficiency. The MEFC with optimized 3D-printed electrodes achieved a maximum current density of 4.64 ± 0.29 mA/cm2, a hydrogen production rate of 5.47 ± 0.13 L-H2/L/d, and a chemical oxygen demand (COD) removal rate of 1.81 ± 0.07 kg/m3/d at an applied voltage of 0.9 V, significantly outperforming most reported MECs. These findings provide a robust framework for the design of high-performance MECs, advancing their potential for large-scale implementation in wastewater treatment and biohydrogen production.