Micro-electroforming metallic bipolar electrodes for mini-DMFC stacks

TL;DR

This paper presents a novel micro-electroforming process to create metallic bipolar plates for mini-DMFC stacks, enabling miniaturization and comparable power density to traditional graphite plates, with improved manufacturability.

Contribution

It introduces a micro-electroforming fabrication method for metallic bipolar plates, facilitating miniaturization of DMFC stacks with comparable performance to conventional materials.

Findings

Maximum power density of 9.3 mW/cm2 at 30°C

Micro-electroforming enables precise micro-fluidic channel fabrication

Metallic bipolar plates are suitable for mini-DMFC stacks

Abstract

This paper describes the development of metallic bipolar plate fabrication using micro-electroforming process for mini-DMFC (direct methanol fuel cell) stacks. Ultraviolet (UV) lithography was used to define micro-fluidic channels using a photomask and exposure process. Micro-fluidic channels mold with 300 micrometers thick and 500 micrometers wide were firstly fabricated in a negative photoresist onto a stainless steel plate. Copper micro-electroforming was used to replicate the micro-fluidic channels mold. Following by sputtering silver (Ag) with 1.2 micrometers thick, the metallic bipolar plates were completed. The silver layer is used for corrosive resistance. The completed mini-DMFC stack is a 2x2 cm2 fuel cell stack including a 1.5x1.5 cm2 MEA (membrane electrode assembly). Several MEAs were assembly into mini-DMFC stacks using the completed metallic bipolar plates. All test results showed the metallic bipolar plates suitable for mini-DMFC stacks. The maximum output power density is 9.3mW/cm2 and current density is 100 mA/cm2 when using 8 vol. % methanol as fuel and operated at temperature 30 degrees C. The output power result is similar to other reports by using conventional graphite bipolar plates. However, conventional graphite bipolar plates have certain difficulty to be machined to such micro-fluidic channels. The proposed micro-electroforming metallic bipolar plates are feasible to miniaturize DMFC stacks for further portable 3C applications.