Environmental remediation using functional nanofibers

Access to safe drinking water is fast becoming a global challenge due to widespread contamination by harmful organic and inorganic pollutants. The commonly used disinfectants, e.g. chlorine, chloramines and ozone, result in the formation of toxic by-products, thus, necessitating the development of new green, low cost, and sustainable disinfection technologies. Nanoscale materials, with high surface-to-volume ratio and reactivity, can potentially be scaled up to develop nanotechnology-based solutions for wastewater remediation. My research group’s focus has been on materials physics and chemistry based strategies for the development of functional nanofiber based membranes with enhanced photocatalytic performance. The membrane will carry out the filtering part, isolating bacteria and most viruses, and the photocatalytic functionality will degrade them to non-toxic by-products under UV or visible-light irradiation.

(a-b) Polymer nanofibers for mitigating PM2.5 in air, (c) Ag2S decorated TiO2 nanofiber for treating organic dyes and (d-e) bacteria in water

Electrocatalysis using carbon nanofibers supported hierarchical nanomaterials

The ever-increasing energy demand has shifted the focus from fossil fuels to cleaner, renewable, and sustainable resources, which has stimulated the development of hydrogen-based energy systems.Fuel/electrolysis cells have been considered as a promising technology because not only do they generate electricity from hydrogen fuels in fuel cell mode, but they can also produce hydrogen from water using electrolysis mode. These are based on hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) for fuel cells and hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) for electrolysis cells.ORR and OER are both four electron transfer processes requiring high driving potentials and their sluggish kinetics limits the overall performance. Noble metal based catalysts like Pt/C for ORR/HER and RuO2/IrO2 for OER are considered as the benchmark catalysts, however, high costs and low durability during long-term use inhibits their practical use. There is a dire need to design a robust, bifunctional, and non-noble metal based catalysts.Work in my research group has focused on designing a low cost and scalable process for in-situ growth of hierarchical carbon nanostructures with adequate N-doping and loaded with metal alloy/oxide nanoparticles which were very promising for these applications.

Energy storage using porous and composite carbon nanofibers

The demand for increased energy and power density in energy storage devices require innovative solutions for new electrode materials/architectures with higher capacities and longer life. One-dimensional (1D) carbon nanomaterials have gained much attention for their usage in electrochemical energy conversion and storage devices as electrode materials due to their large surface area, high chemical and thermal stability, high conductivity and relatively low cost. Enhanced surface area in case of porous carbon materials further complement their electrochemical behavior. Currently, we are investigating the fundamental correlation between pore characteristics of carbon nanofibers and their electrochemical performance. In addition to optimizing the pore characteristics, the electrochemical storage capacities of carbon materials can be further enhanced by incorporating second phase materials. Our work is focused on designing hierarchical and multi-scale carbon based nanocomposites for enhanced energy storage such as lithium ion batteries and supercapacitors. We were not able to test our synthesized materials for batteries due to limitation in experimental facilities. However, investigated these materials for supercapacitor applications.

Multi-walled carbon nanotubes grown over carbon nanofibers using CVD

Structural nanocomposites using surface modulated carbon nanofibers

Nanotechnology offers unique opportunities to develop novel material combinations, known as nano-composites, which potentially can bypass typical material performance trade-offs. Electrospun carbon nanofibers have many advantages such as being long, continuous, and in aligned form. They can be incorporated in polymer matrix composites for enhanced matrix strengthening and toughening. Moreover, these carbon nanofibers can show synergistic toughening effect if their surfaces have slight undulations which have been proven by theoretical models but not been investigated experimentally mainly due to difficulty in synthesizing such materials and limitations in nanoscale testing. We dedicated significant effort to develop nanocomposites with chemically and physically modulated carbon nanofibers for unprecedented enhancement in strengthening and toughening. Their interfacial properties were controlled to enhance their overall performance.

Polymer nancomposites containing functionalized carbon nanofibers