Tailoring the surface features of CaWO4 by coupling with tubular g-C3N4 for enhanced solar photocatalysis and thermal energy storage

Rising energy and environmental crisis has led researchers to develop novel bifunctional materials. Herein, we report the construction of bifunctional hybrid materials for thermal energy storage and solar photocatalytic systems. Such a novel type of green material including calcium tungstate (CaWO4) and tubular graphitic carbon nitride (g-C3N4) was successfully fabricated via thermal mixing method. X-ray diffraction analysis confirmed the formation of both CaWO4 and g-C3N4 in the composite while morphological analyses verified the successful attachment of CaWO4 particles over the tubular g-C3N4 structure. The wide band gap energy (3.6 eV) of the pristine CaWO4 significantly decreased to 1.85 eV after coupling with g-C3N4. The hybrid catalyst showed superior photocatalytic degradation of Allura red (79.3 % within 120 min) and the rate constant was found 31.3-folds higher compared to pristine CaWO4 (13.3 % removal), which was ascribed to strong light harvesting, increased surface area, smaller crystallite size and fast electron transfer rate. In addition to catalytic functionality, the synthesized pristine and hybrid catalysts were also used in the preparation of lauric acid-based phase change materials (PCMs) and thermal properties of different fillers were examined. The 1 wt% CaWO4/g-C3N4 filler loaded composite displayed 13.03 % increment in heat storage rate (oC/s) when compared with lauric acid, demonstrating the essential role of the hybrid material over the PCM structure. The as-prepared hybrid materials displayed a bifunctional activity derived from incorporation of carbon nitride and thus verified a great potential for different applications due to their enhanced features.