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

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) WS₂ 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-WS₂ 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.