Electrospun, flexible and reusable nanofiber mat of graphitic carbon nitride: Photocatalytic reduction of hexavalent chromium.

Nanofiber mat of graphitic carbon nitride (g-CN) was fabricated from g-CN/polyvinylidene fluoride (PVDF) composite using an electrospinning technique. The mat was characterized with SEM, AFM, XRD, FTIR and photoluminescence (PL) spectroscopy. This nanofiber mat is flexible and can be folded or rolled without losing any structural integrity. The nanofiber mat also demonstrates self-cleaning properties in aqueous medium as demonstrated with two dyes, methylene blue and rhodamine B. Hexavalent chromium was successfully reduced by the nanofiber mat of g-CN under visible light. Although the rate of reduction of Cr(VI) was very slow in presence of nanofiber mat of g-CN alone, it was enhanced significantly in presence of trace amounts (0.3%) formic acid. Formic acid played the dual role of hole scavenging agent of g-CN to make the photogenerated electrons more available to the reaction and generating H and CO in the system that can also directly reduce Cr(VI) onto Cr(III). The nanofiber mat demonstrated excellent cyclability for photocatalytic reduction of Cr(VI) and self-cleaning properties in presence of visible light.