Nanocellulose in conductive materials Lauri Matikainen

Introduction  Conductivity  Utilization  Ionic solutions  Plasmas  Superconductors  Quantity: σ (sigma), Unit: S/cm (Siemens – Reciprocal to resistance and Ohm)  Capacitance  C = ϵ 0 ϵ r A/d, Unit: F (Faraday)  Describes the capacity to conserve electricity

Capacitors Supercapacitor Conventional capacitor 1.Power source 2.Collector 3.Polarized electrode 4.Hemholz double layer 5.Electrolyte having positive and negative ions (uncharged) 6.Separator Target in this study: To enhance the electrostatic attraction of electrodes

Background  Typical material of an electrode: Active carbon, graphene, carbon nanotube, etc.  Suggested material of an electrode: Cellulose nanocrystals/Polypyrrole – CNC/PPy  Comparable properties: Flexible, lightweight, “wearable”  The properties follow the PPy/OH relation (Polypyrrole to CNC OH-groups)  The OH-groups were introduced to CNC by TEMPO-oxidation

Results Figure 1: Optimal PPy/OH ratio = 16:1 The one-dimensional structure of CNC contributes to the conductivity Figure 2: The relation of weight% to temperature between the following combinations: TempoCNC, PPyCNC, and Pure PPy Figure 3: PPy-CNC blend used as a series circuit

Capacitance comparison Substance Specific capacitance (F/g) CNC/PPy 248 Active carbon 100 Graphene (theoretical) 550 Single-walled nanotubes (SWNT) 180 Multi-walled nanotubes (MWNT) 102

Conclusion  CNC/polypyrrole blend is a convenient alternative to enhance the performance of supercapacitors  CNC is made conductive by TEMPO oxidation, which adds carboxylate groups possessing a surface charge  By grafting, polypyrrole end groups can be added to CNC, which improves its advantages  Being flexible, lightweight and wearable, CNC/PPy systems are a competitive alternative for carbon derivatives to be used as electrodes in the future

References 1. Pearson International Edition: Wolfson Essential University Physics, Volume Wu, X. et. al. : Cost-effective and Scalable Chemical Synthesis of Conductive Cellulose Nanocrystals for High-performance Supercapacitors. Electrochimica Acta, Lecture slides: Cellulose Physical Aspects. Orlando Rojas, 2015.