Aerogels Made of Few-Layer WS₂ Nanosheets and Nitrogen-Doped Graphene for Photocatalytic Degradation of Caffeine

Abstract

As a spontaneous renewable energy-based technology, with an astonishing ability to destroy recalcitrant organic pollutants under ambient conditions, solar-driven heterogeneous photocatalysis has sparked immense interest over the past decade. However, creating photocatalysts with astounding visible-light harnessing capacity and undemanding recuperation persists as a significant hurdle to the widespread exploitation of photocatalysis in water treatment. Herein, we propose a potentially nontoxic, robust, durable, and self-supporting photocatalyst, based on the in situ growth of few-layer (FL) WS 2 nanosheets on the interpenetrating channels of nitrogen (N)-doped graphene aerogel (henceforth denoted as "WNGA"). Constructed through a mild hydrothermal processing scheme, WNGA shows self-floating capability, exceptional mechanical resilience, and remarkable solar absorption in the visible range. In addition, the coexistence of pyridinic N species and FL-WS 2 clusters synergistically provides surplus active sites for catalytic reactions. Besides, the interconnected conductive networks of WNGA coherently upregulate charge separation and transfer in 3D. As a result of these beneficial attributes, WNGA presents prominent photocatalytic activity and excellent recycling stability. For instance, through a combination of adsorption and partial oxidation, WNGA can dissociate up to 93% caffeine, the most widely consumed psychoactive substance, into innocuous products over multiple cycles. As a figure-of-merit for the commercial potential of WNGA, we also demonstrate the photocatalytic degradation of caffeine in four different real matrixes, viz., tap water, pond water, municipal wastewater, and hospital wastewater. The exceptional photocatalytic properties, improved durability, and facile retrieval opportunities validate the application potential of WNGA to eliminate psychoactive substances in aqueous environments.

Biomass-based graphene aerogel for the removal of emerging pollutants from wastewater

“…Graphene aerogels have unique properties which make them promising materials for water remediation. 55 In this subsection, we focused on the potential of graphene aerogels for the removal of various emerging contaminants. High surface area and the presence of functional groups on the surface of graphene aerogels enable strong adsorption interactions with emerging water contaminants.…”

“…62 A WS 2 nanosheet incorporated N-doped rGO aerogel showed photodegradation of caffeine up to 93% within 180 min in different real matrices. 55 The N-doped graphene aerogel demonstrated catalytic degradation of antibiotics from wastewater. The as-synthesized sample showed superior catalytic activity towards ibuprofen because of the synergistic effects of the porous structure and N-doping in the sp 2 -hybridized aerogel.…”

“…Photocatalytic degradation is an effective, low cost, excellent oxidation ability and ecofriendly technology which make it superior over other competing processes for the complete degradation of emerging pollutants from wastewater. Various materials such as ZnO, 135 TiO 2 , 136 BiVO 4 , 137 Bi 2 S 3 , 137 WS 2 , 55 etc. have been utilized as photocatalysts.…”

“…11a. 55 When the visible light is incident on the surface of the WNGA photocatalyst, induced ˙OH reacts with the imidazole ring of caffeine to produce m / z 210 (C1), m / z 229 (C2), and m / z 246 (C3) as shown in pathway I (Fig. 11a).…”

“…These intermediate products may perform ring fragmentation reactions in the presence of reactive oxygen species and holes which result in formation of various low-molecular-weight hydrocarbons (C7–C12) which are finally mineralized to NO 3 − , H 2 O, CO 2 , and NH 4 + . 55 For incessant and efficient degradation of emerging pollutants from water, microspheres of silver phosphate and GO aerogel (SGAM) with radially oriented microchannels were developed. 139 The efficient photodegradation activity was due to the incorporation of silver phosphate in the honeycomb structure of the GO aerogel because of the interaction between silver phosphate and GO sheets, which accelerates the electron transfer (Fig.…”