Anchovy-derived nitrogen and sulfur co-doped porous carbon materials for high-performance supercapacitors and dye-sensitized solar cells

Abstract

Anchovies are a popular food worldwide, but a large amount of the anchovy is discarded as food waste in Korea, after cooking for anchovy juices. In order to reduce and reuse the food waste of anchovies, anchovy-derived nitrogen and sulfur co-doped porous carbons (AnCs) were prepared by a simple carbonization and alkali activation method for use as superior electrodes in supercapacitors and dye-sensitized solar cells (DSSCs). AnCs with a high specific surface area and moderate heteroatom (N and S) doping levels enabled both applications. The chemical composition and porosity of AnC materials were characterized by X-ray photoelectron spectroscopy (XPS) and nitrogen sorption isotherm measurements, exhibiting high nitrogen and sulfur contents (2.09 and 0.81 atom%, respectively) and specific surface area (2622 m² g⁻¹). When used as a supercapacitor electrode, the AnC-900-2.0 sample exhibited superior specific capacitance of 613 F g⁻¹ in 6 M KOH electrolyte at a current density of 1 A g⁻¹ and good long-term stability. Moreover, the electrocatalytic activities of AnCs were investigated with a symmetrical dummy cell by using two identical electrodes through electrochemical impedance spectroscopy (EIS). The AnC as a counter electrode (CE) for DSSCs exhibited much better electrocatalytic performance than a Pt CE toward the Co(bpy)₃^2+/3+ redox couple. An AnC-900-2.0-based DSSC employing a SM-315 porphyrin as a superior organic sensitizer led to a power conversion efficiency (PCE) of 12.72%, which is to the best of our knowledge the highest value reported for DSSCs based on carbon nanomaterials as CEs, compared to Pt-CE (12.23%), due to an enhanced fill factor caused by its better electrocatalytic ability. The superior specific capacitance and excellent photovoltaic performance could be due to high specific surface area and moderate heteroatom doping level.