Ni Ink-Catalyzed Conversion of a Waste Polystyrene–Sugar Composite to Graphitic Carbon for Electric Double-Layer Supercapacitors

Abstract

The disposal of organic waste materials such as polymers is a serious problem to natural ecosystems as some of them can be non-biodegradable and potentially toxic. Thus, there is immense interest in developing processes that convert waste polystyrene into useable carbon. In this work, we developed a unique approach for obtaining graphitic carbon from waste polystyrene as a raw carbon source. The conversion process is catalyzed using the Ni-butanethiolate ink in ultralow quantities under an optimized temperature (800 °C) in the presence of 5% hydrogen in nitrogen. Interestingly, macroporous sugar cubes are used as a soft template to hold polystyrene and the catalyst together during decomposition, eliminating the need for a high-pressure source for retaining carbon for graphitization at high temperatures. An additional step of hydrogen annealing for pyrolyzed carbon nullifies the surface effects and improves the graphitization, reduces the point defects, and enhances the crystallinity of carbon and electrical conductivity specifically required for an electric double-layer capacitor (EDLC). The SPC8H-based graphitic carbon electrode exhibits perfect rectangular cyclic voltammetry characteristics with a symmetric triangular charge–discharge curve and a specific capacitance of ∼158 F/g at 1 A/g. The two-electrode EDLC device demonstrated excellent cyclic stability with a capacitance retention of ∼90% even after 10,000 cycles. This study reveals that the trashed polystyrene waste could be transformed into highly crystalline, graphitic carbon electrodes for energy storage devices. This indeed offers an alternative and sustainable approach with a low price to high-performance ratio that can probably manage the issue of white pollution at a commercial scale.

Visibly transparent supercapacitors

“…The more commonly used carbon-based electrode materials like CNTs, graphene, and carbon black are a few EDLC electrodes. 30 Pseudocapacitance stores charges via a reversible faradaic charge transfer.…”

“…The more commonly used carbon-based electrode materials like CNTs, graphene, and carbon black are a few EDLC electrodes. 30 Pseudocapacitance stores charges via a reversible faradaic charge transfer. The typical examples of pseudocapacitance materials are transition metal oxides (MnO 2 and Co 3 O 4 ), hydroxides (Ni(OH) 2 ), carbides (Ti 3 C 2 ), and sulfides (CuS and MoS 2 ); conducting polymers like polyaniline (PANI) and polypyrrole (PPy).…”

Waste plastic to energy storage materials: a state-of-the-art review

“…Zhang et al 72 prepared porous carbon materials using PS as the carbon source and SiO 2 as the hard template. Urgunde et al 73 introduced carbonizing PS with a sugar cube as the template to produce carbon materials under the catalysis of Ni. Carbon materials have been widely used in the manufacturing of supercapacitors.…”

Nickel Cobaltite Nanoplate‐Based Electrochemical Sensing Platform from Printable Inks for Simultaneous Detection of Dopamine and Uric Acid

“…Co hexadecanethiolate (Co-HDT) and Ni butanethiolate (Ni-BT) precursors were synthesized using a general two-step method reported previously. [25][26][27][28]…”