Synergistic Effect of Metal Complex and Dual Doped Graphitic Carbon Nitride for Superior Photocatalytic Hydrogen Evolution
Bishal Das, Devipriya Gogoi, Meghali Devi, Siddhartha Sankar Dhar, Nageswara Rao Peela
Abstract
The feeble photoinduced charge separation ability of pristine graphitic carbon nitride largely reduces its photocatalytic hydrogen evolution and thereby limits its practical application. Herein to increase effective charge separation in the graphitic carbon nitride system, consecutive modifications have been made with dual doping of sodium and sulfur followed by grafting of a VO(acac)2 complex. The efficient doping and subsequent grafting in the novel photocatalyst VNS-GC was verified by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy/energy dispersive X-ray spectroscopy, high resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. A higher absorbance intensity and lower band gap, photoluminescence intensity, and EIS spectrum ensure a more elevated photocatalytic efficiency in VNS-GC than pristine graphitic carbon nitride (GC). The greater efficiency of the as-synthesized catalyst over bulk GC was experimentally employed through photocatalytic hydrogen production. It was found that the H2 production using VNS-GC was at 310.63 μmol g–1 h–1 which was 4.3 times higher than that with GC. A higher photocatalytic H2 evolution efficiency was predominantly attributed to the lower recombination rate of the charge carriers as is also evident from TR-PL and Nquist plots, thus overcoming the structural limitations in GC. Moreover, the VNS-GC catalyst was also found to have good stability through repeated cycles of experiments.