Synergistic Effect of Metal Complex and Dual Doped Graphitic Carbon Nitride for Superior Photocatalytic Hydrogen Evolution

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.

Efficient Oxygen Doping of Graphitic Carbon Nitride by Green Microwave Irradiation for High-Performance Supercapacitor Electrode Material

“…The stretching mode of the C–N heterocycle displayed a sharp peak in the 1210–1700 cm –1 range, and ring breath modes of the s -triazine motifs were observed at 805 cm –1 . Another small peak at 710 cm –1 was observed for out-of-plane bending of −NH 2 groups. , OGCN-M gives an IR spectrum akin to that of GCN with slight disparities. The s -triazine ring breath modes in OGCN-H and OGCN-M at 805 cm –1 weakened owing to the addition of O atoms replacing the secondary N atoms in the GCN framework.…”

“…The sharp peak at 1203 cm –1 was attributed to the bending vibration of sp 2 C, and the blueshift in OGCN-H and OGCN-M was attributed to exfoliation due to hydrothermal and microwave processes . The major band in the 1350–1800 cm –1 range was attributed to fundamental C–N stretching of GCN . The distinctive D and G bands for GCN were observed at 1435 and 1655 cm –1 , and for OGCN-M, those are observed at 1442 and 1664 cm –1 , respectively .…”

“…Another small peak at 710 cm −1 was observed for out-of-plane bending of −NH 2 groups. 32,36 OGCN-M gives an IR spectrum akin to that of GCN with slight disparities. The s-triazine ring breath modes in OGCN-H and OGCN-M at 805 cm −1 weakened owing to the addition of O atoms replacing the secondary N atoms in the GCN framework.…”

“…Another characteristic satellite peak centered at 402.1 eV was also obtained as shown in Figure 3b. 16,36 The area under signals for (C−N�C) is slightly decreased as shown in Table S4, indicating a reduced amount of two coordinated N atoms in OGCN-M compared with that in GCN. The slight shift in the binding energies of the C 1s and N 1s spectra of OGCN-M was attributed to the weakened electron screening effect due to incorporation of oxygen in the s-triazine matrix.…”

Organic–inorganic hybrid photocatalyst consisting of a highly conjugated metal complex and graphitic carbon nitride for efficient hydrogen evolution and Cr(vi) reduction

“…However, an increase in the intensity of these peaks in Cu-Por/GCN is attributed to the interaction of the metal complex with the GCN layers. 30,31 The FT-IR spectra of Cu-Por are demonstrated in ESI Fig. S3.…”