A novel technique to manufacture carbon-free gas diffusion layer for polymer electrolyte membrane fuel cell application by a selective laser sintering (3D Printing)
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A Gas Diffusion Layer (GDL) is an integral component of a PEM fuel cell stack, which plays a significant role in determining its performance, durability and the dynamic characteristics. An ideal GDL function to simultaneously transport three of the five essential elements, namely gas, water and heat involved in the electrochemical reaction. In addition, it also transports the electron produced in the electrochemical reaction and serves as an armour to safeguard the membrane (Nafion), which is a delicate and most expensive component of the PEM fuel cell stack. However, the conventional carbon-based GDL materials suffer from degradation issues during PEM fuel cell operation, and the predominant one is the electrochemical voltage oxidation. The electrochemical degradation is due to the oxidation of the carbon present in the carbon paper to carbon dioxide especially at voltages greater than 0.207 V on a standard hydrogen electrode (SHE). Operating a PEM fuel cell stack at a low voltage (<0.207 V) is not practically possible since it can severely aggravate the operating efficiency and power density of the PEM fuel cell stack. Incorporating a GDL that is free from carbon can be a promising solution to circumvent these issues about the electrochemical oxidation. Also, the conventional GDL manufacturing technique had a tedious and complicated process, which involves multiple stages. These multiple production stages also led to its high manufacturing costs and increased lead-time. The proposed research work is estimated to address both these issues of GDL durability and manufacturing costs. The additive manufacturing method incorporating selective laser sintering (SLS) technique aims to provide a comprehensive solution to address both these issues. The concept of SLS is that the laser beam robotically scans the composite powder (base and conductive powder) at points in a space defined by a 3D model, fusing and subsequently binding the composite material together to create a solid-state structure. Thus, SLS can be a favourable route to fabricate a carbon-free GDL as well as to reduce its manufacturing costs and lead-time. At the end of the experimental investigation, holistic characterisation studies were performed to have a general insight on the characteristics of the proposed material. Valuable information is extrapolated from the characterisation studies, which can assist, to fine-tune the material selection and SLS process parameter. In addition, ground-breaking findings from the perspective of the structural and functional relationship of the proposed GDL specimen had been made considering the first principles of the diverse field of engineering. Though the performance based on the experimental results are inferior, it gives us the buoyancy that the proposed proof of concept can be a promising route to fabricate durable and cost-effective gas diffusion layers based on the critical observations of the SLS process.