The Paris Accord has set in motion aggressive policies to combat climate change. G20 economies produce 80% of the world’s greenhouse gases (GHGs). With its rapidly growing economy, India needs to balance the prosperity ambition while sharing the tremendous burden of keeping the rising temperature level well below 2 o C. To combat this eminent issue, low-temperature polymer electrolyte based electrochemical energy conversion and storage systems present one of the sustainable long-term solutions; not just to reduce GHG emissions, but in fact cleanup of present GHGs. One such technology is polymer electrolyte fuel cell (PEFC) which directly converts the chemical energy of hydrogen fuel and oxygen into electricity with heat and water as bi-products. However, these technologies are still in the nascent stage, mostly suffering from synchronization of performance, cost, and durability – three important aspects for commercialization. All three are intimately linked to technical parameters such as reactant transport and catalyst activity, which are ultimately related to material set parameters. In a PEFC, several different transport processes over multiple lengths occur. Gases and liquid water transport occurs serially through a porous carbon medium called gas diffusion layer (~100 um thick, ~10 um pore size), a nanoporous-nanocomposite catalyst layer (~10 um thick, ~10-100 nm pore size), and the ionomer (~1-10 nm thick, and ~1 Å domain size) to the catalyst surface. Heat transport also occurs through these material phases. Electrons are conducted through the carbon phase in the diffusion layer and catalyst layer. Protons (ionic species) are transported through the nano scale domains of ~10 um thick polymer electrolyte and ~10 nm thick ionomer films. The transport process at each scale is relevant to the PEFC performance. The cost is indirectly linked to the performance and directly via the usage of expensive platinum catalyst. For example, poor in operando utilization of catalyst effectively results in poor performance for a higher cost of catalyst. Thus, both transport and material characterization is essential. This presentation discusses the investigation transport of reactants from micro-scale to nano-scale, which encompasses: transport in porous media, design of a novel catalyst layer, and ionomer thin film properties.

 

 

Dr. Udit N. Shrivastava holds a PhD in Mechanical Engineering from Michigan Technological University. Currently, he is a Canada First Research Excellence Forum (CFREF) postdoctoral fellow at the University of Calgary, working under the supervision of Professor Kunal Karan. During his PhD and postdoc, he developed advance electrochemical diagnostic tools for fuel cell application and worked on both industrial and federal government funded projects namely General Motors, Ballard Power Systems, and NSERC. At present, his research work is focused on the characterization of nano structured materials and ionomer thin films for application in fuel cell and other electrochemical systems. He has authored seven international publications and several others are in review and process of submission.