Akhmad Syoufian's research while affiliated with Universitas Gadjah Mada and other places

... Zirconium titanate (ZrTiO 4 ) modified by the doping method will decrease the band gap to visible light. Several studies have reported that doping can be done with metals such as Fe [26], Mn [27], and Zn [28] and also non-metals such as N [29] and C [30]. In this study, copper (Cu) and nitrogen (N) were chosen as dopants because they have good charge-carrier separation efficiency. ...

... The FTIR spectra of the SiO 2 catalyst indicated a wide absorption peak at the wavenumber 1080-1087 cm −1 believed to be the asymmetric stretching vibration of Si-O-Si [8]. The absorption at 802 cm −1 indicated the symmetric stretching vibrations of Si-O-Si, whereas and 462 cm −1 indicated the bending vibrations of SiO 2 as well as Si-O-Si deformation [16,17]. There were also absorptions at around 1635 cm −1 and 3441-3448 cm −1 which indicated the presence of a silanol group [18]. ...

... Higher conversion is achievable as confirmed by the higher yield (greater than90%) by optimized catalyst loading to 7.61 wt% [121]. From some literatures, it is conclusively obtained that sulfated zirconia is not feasible for palm oil conversion as less conversion at longer time of reaction and higher oil to methanol ration required compared to the use of other oil feedstocks [122,123]. ...

... These results are found to be consistent with the acidity features. A similar found also reported by a previous study, which described that vacant SiO 2 shows a lower acidity value than the silica-supported metal, leading to low conversion during the hydrocracking process [82]. A catalyst with a highly acidic site could effectively promote the radical hydrogen uptake that ultimately reacted with the feed, consequently increasing the liquid yield [83]. ...

... This is primarily due to the non-renewable nature of petroleum fuels, which require an extended period for recharge. 1 Worldwide energy consumption has risen in parallel with the expansion of the industrial sector, thus encouraging the necessary exploration of renewable and environmentally acceptable alternative energy sources. 2 Biofuels are among the most intriguing alternative energy sources currently being explored because they are ecofriendly and sustainable. They are broadly extracted from a clean energy source such as vegetable oil which provides noncontaining nitrogen and sulfur chemicals. ...

... As a result, the ZrO 2 particles are completely attached to the surface of the rGO nanosheets. The stretching vibration peak of 1483 cm À1 in the rGO/ZrO 2 /SO 4 2À / Cu spectrum is due to the interaction between the oxygencontaining groups of rGO and Zr (IV), and two vibrational bands at 1483 cm À1 and 1395 cm À1 [60], which were attributed to the formation of either a monodentate or bidentate complex but were very weakly intense in the IR spectrum shown in figure A. All samples show distinctive peaks at 1103, 1077, and 983 cm À1 (shoulder) in the FT-IR spectra of figures A and B, which correspond to the asymmetric or symmetric stretching vibrations of S¼O or SeO bonds. The coordinated bidentate sulphate ions attached to a metal cation exhibit this type of vibration. ...

... Ore et al. [15] reported that the number of Brønsted and Lewis acid sites depends on the SO4 2− concentration present on the catalyst surface. Sulfation with optimum sulfate concentration can increase the catalytic activity of the catalyst, while the decrease in catalyst acidity with increasing temperature occurs due to dehydration of protonic sites and loss of SO4 2− groups on the surface of the catalyst [38][39][40]. Qualitatively, the number of Brønsted and Lewis acid sites can be observed absorption spectra intensity that denotes the interaction between the catalyst acid sites and NH3 [41]. Figure 5 presents the FTIR spectra of the catalyst after the acidity test. The absorption peak at 1119-1126 cm −1 indicates the presence of NH3 coordinated to the Lewis acid site. ...

... Moreover, mesoporous silica generated from natural sand can be used as catalyst for the production of biofuel. The catalysts are synthesized by a CTAB template method and then doped with Mo via a wet impregnation method (Alisha et al. 2022). ...

... This result is higher than previous research that produces 5.59% of hydrocarbon from α-cellulose. 33 Meanwhile, Trisunaryanti et al. 34 produce 27.28% of the hydrocarbon from coconut oil found using Co-mesoporous silica as a catalyst. This difference value is probably due to this study's higher surface area of silica. ...

... An absorption spectrum at 1441 cm −1 region indicates the presence of Mn dopant in the composites [34]. At the low wavenumber region, the absorption belonged to the vibration of Ti-O-Ti, Mn-O-Ti, and Mn-O are found around 400-700 cm −1 [35]. Sharp peaks observed around 500 cm −1 correspond to the stretching vibration of Zr-O of the ZrO 2 phase [36]. ...