Engineering a 3D porous carbon sponge as a self-floating solar energy utilization platform for photothermal oil spill recovery and photocatalytic H2 evolution

Abstract

Lightweight 3D porous self-floating platforms with enriched light–water–air–material interactive interfaces are promising candidates to promote solar energy utilization, regarding the requirements of solar-inspired reactions such as photothermal spill oil recovery and photocatalytic hydrogen production. Herein, we report a facile and controllable method to prepare lightweight porous carbon sponges by using low-cost melamine-formaldehyde (MF) foams as an environmental-friendly template and raw material, which are a widely-used mass disposal building solid waste with high porosity. Scanning electron microscopy shows the natural 100 μm level porous network structure of the MF foams is retained after carbonization. Nitrogen adsorption–desorption isotherms and corresponding pore size distributions clearly indicate the carbon sponges have unique hierarchical mesoporous features, which are beneficial for remediation of spilt oil or composite photocatalysis. X-ray diffraction data and Raman spectra verify the partial graphitization of the mesoporous carbon sponges, and Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy confirm the presence of N- and O-containing functional groups. Joule-heating performance testing in a simulated oil spill case under sunlight shows that the carbon sponges are superior over the supported graphene containing a positive control in terms of heating and rheological regulation effects, and thus are useful in oil spill recovery. Further photocatalytic hydrogen evolution experiments using the graphitic carbon nitride (g-C₃N₄) semiconductor-coated carbon sponge suggest the successful assembly of an efficient carbon/g-C₃N₄ H₂ production platform. Hence, this low-cost waste MF foam-derived carbon sponge platform with high mechanical applicability and durability is promising for use in various energy and environmental applications.