Pt-free graphene oxide-hydrogen membrane fuel cells (GOHMFCs)

Abstract

High-performance conventional proton exchange membrane fuel cells (PEMFCs) typically rely on expensive Pt/C as the catalyst for the hydrogen oxidation reaction (HOR) at the anode and the oxygen reduction reaction (ORR) at the cathode, which suffers from CO poisoning. As a result, there is a surging interest in developing precious metal-free electrocatalysts in fuel cells and metal-air batteries. A promising candidate is graphene, a one-atom-thick monolayer with a 2-dimensional (2-D) hexagonal honeycomb lattice of carbon, which offers an ideal replacement opportunity as an electrocatalyst for the ORR due to its high catalytic activity and tolerance against poisoning. In this study, nitrogen-doped reduced graphene oxide (N-rGO), a low-cost and precious metal-free electrocatalyst for ORR, are synthesized using a hydrothermal method using a low-cost industrial material ammonium formate (NH4HCO2) as both the reductant agent and nitrogen source. Here, we have confirmed the successful formation of N-rGO and reduced graphene oxide (rGO) through a series of analyses on the microstructure, molecular bonding, nanometric composition, and surface chemistry of the materials and their ORR activity. By integrating a membrane electrode assembly (MEA) with MPTS-modified graphene oxide (GO) composite electrolyte (MGC-50), which contains a 50 wt% ratio of (3-mercaptopropyl)trimethoxysilane (MPTS) and GO, we have developed a safe and scalable method for Pt/C-free electrocatalyst application in graphene oxide-hydrogen membrane fuel cells (GOHMFCs). The best performing catalyst (N-rGO-AA@180) exhibited the maximum power density (MPD) of 17.57 mW/cm2 with a load current density (LCD) of 87.50 mA/cm2, significantly better than those of rGO@300, which has an MPD of 5.70 mW/cm2 with an LCD of 23.90 mA/cm2, both measured at 40 °C.