Photocatalytic CO2 reduction to CO and CH4 using g-C3N4/RGO on titania nanotube arrays (TNTAs)

Enhanced Photocatalytic CO2 Reduction to CH4 Using Novel Ternary Photocatalyst RGO/Au-TNTAs

“…A cross-sectional view image is depicted in Figure 3c, revealing an efficient growth of one-dimensional, vertically oriented TiO2 nanotubes over the Ti metal substrate with an excellent tube-length reaching up to 900 nm. The higher length of TiO2 nanotubes provides more chances for contact between the nanotubes with the CO2 and H2O molecules [23,48]. These morphological results of TNTAs are consistent with the literature reported by Ikreedeegh & Tahir [23] Devi et al [43], Sim et al [49], Low et al [50], and Lee and Kim [51], revealing the proper anodization with sufficient annealing for achieving hierarchical, vertically orientated, free of surface-damage and open-pores TNTAs.…”

“…The higher length of TiO 2 nanotubes provides more chances for contact between the nanotubes with the CO 2 and H 2 O molecules [23,48]. These morphological results of TNTAs are consistent with the literature reported by Ikreedeegh & Tahir [23], Devi et al [43], Sim et al [49], Low et al [50], and Lee and Kim [51], revealing the proper anodization with sufficient annealing for achieving hierarchical, vertically orientated, free of surface-damage and open-pores TNTAs. The Au nanoparticles have been successfully incorporated into the nanotubes through the electrochemical deposition method.…”

“…After the reduction, all the peaks corresponding to the stretching vibration of oxygen-containing functional groups (O-H and C-O) were significantly reduced as a result of the de-oxygenation process [25]. This de-oxygenation has no negative effect on CO 2 photoreduction [23,48]. The RGO peaks in the ternary composite also confirm the good decoration of RGO nanosheets on TNTAs.…”

“…The TNTAs after annealing displayed a sharp diffraction peak at 25.5° corresponding to the (101) plane of TiO2 anatase (DB card number 9015929), more significant peaks were observed at the 2θ: 25.5°, 38.6°, 48.2°, 54.3°, 55.3° indexed to (101), (004), ( 200), (105), (211) planes of tetragonal anatase phases of TiO2, respectively [58][59][60] while no peaks were detected for the TiO2 rutile phase. It is evident from Figure 5, the peak at 23.5° and 42.8° correspond to the plane (002) and (111) of RGO [23]. The XRD patterns of Au-TNTs and RGO/Au-TNTAs samples displayed two noteworthy major diffraction peaks at 2θ: 39.2° and 77.3°, attributed to the (111) and (311) crystal planes of Au, indicating the successful deposition of Au nanoparticles [61,62].…”

“…Recently, the TiO 2 in the form of nanotube arrays (TNTAs) has attracted much attention due to the advantage of orthogonalization of light absorption by offering more scattering and trapping of light [21]. Moreover, the TiO 2 nanotube system facilitates the flow of electrons among the nanotube walls providing more shortcuts compared to lengthened electron pathways in nanoparticle systems [22][23][24]. However, the TNTAs photocatalyst still performs poorly under visible light due to its wide band gap (3.0-3.2 eV) which limits its application only to the UV range.…”