[
    {
        "id": 1,
        "chunk": "# Direct Growth of Bio-Graphene Using Modified-Chemical Vapor Deposition For Straight-Forward Characterization  \n\nM.D. Nurhafizah \\*, A.A. Azahar , N. Abdullah  \n\nSchool of Physics, Universiti Sains Malaysia, 11800 USM, Minden Penang, Malaysia",
        "category": " Abstract"
    },
    {
        "id": 2,
        "chunk": "# H I G H L I G H T S",
        "category": " Abstract"
    },
    {
        "id": 3,
        "chunk": "# G R A P H I C A L  A B S T R A C T  \n\nOil Palm Shell biomass conversion to Bio-Graphene via pyrolysis and CVD.   \n• Partial and total covers growing settings were evaluated on Bio-Graphene growth.   \n• Faster characterization through direct deposition of Bio-Graphene on a silicon wafer.   \nBetter closed growing settings facilitate the growth of high-quality BioGraphene.  \n\n![](images/9cc379e22ff8561303e1280f50bb496d576e6d65b8ab6286afbcc88e40f0ef12.jpg)",
        "category": " Abstract"
    },
    {
        "id": 4,
        "chunk": "# A R T I C L E  I N F O",
        "category": " Abstract"
    },
    {
        "id": 5,
        "chunk": "# A B S T R A C T  \n\nKeywords:   \nGraphene   \nAlumina Boat   \nPyrolysis   \nOil Palm Shell   \nBiochar  \n\nOil Palm Shell (OPS) is subjected to heating, resulting in gaseous compound release. These compounds are deposited on the substrate to produce Bio-Graphene. Through Chemical Vapor Deposition (CVD), the process is optimized by growing environment parameters during the production process. This process involves the controlled deposition of gaseous compounds onto a substrate under two different positions of the alumina boat (ABC-1 and ABC-2). Direct deposition on silicon wafers eliminated etching and transfer sequences, simplifying Bio-Graphene characterization. Field Emission Scanning Electron Microscope, Atomic Force Microscope, Raman Spectroscopy, X-ray diffraction, and I-V measurement were employed to characterize the Bio-Graphene. The findings revealed that the better-closed settings (ABC-2) facilitated the growth of high-quality Bio-Graphene with better crystallinity, detectable growth spurt, estimated few-layer thickness, larger growth area, and lower surface roughness. Optimizing the deposition environment at ABC-2 significantly enhances the quality and crystallinity of Bio-Graphene from OPS, paving the way for future applications.",
        "category": " Abstract"
    },
    {
        "id": 6,
        "chunk": "# 1. Introduction  \n\nPalm oil production is a global economic venture that promotes the economic growth of many countries that could supply them. In 2015, global production of palm oil reached 63 million tons, with Indonesia contributing the highest percentage at $53\\%$ , it is followed by Malaysia at $33\\%$ and then by Thailand at $3\\%$ (Mahlia et al., 2019). Palm oil holds immense significance not only in meeting the global demand but also as a vital economic contributor to Southeast Asian (SEA) countries. Palm oil is obtained by planting, growing, and harvesting palm oil plants over hectares of palm oil plantation. The production of palm oil generates a substantial amount of biomass waste, including various types of branching waste, at every stage of the production process (Nabila et al., 2023). Thus, an issue arises when the industry generates a substantial amount of waste that possesses a significant impact on waste manage­ ment. One of the palm oil wastes is Oil Palm Shell (OPS) which is be­ tween the hard seed and flesh mesocarp of the palm oil fruit (Omar et al., 2018). Improper waste management can lead to air pollution, water pollution, visual pollution, and odor pollution that results in damage to the natural environment, including the loss of biodiversity and ecosystem.  \n\nOil palm shell produces solid amorphous carbon biochar, a complex mixture of organic compounds bio-oil, and gaseous compounds biogas while undergoing pyrolysis. The biogas produced from oil palm shells are composed of methane $\\mathrm{(CH}_{4}\\mathrm{)}$ , carbon dioxide $\\left(\\mathsf{C O}_{2}\\right)$ , and small amounts of other gases such as nitrogen $\\left(\\mathrm{N}_{2}\\right)$ and hydrogen $\\left(\\mathrm{H}_{2}\\right)$ (Maithel, 2009). Typically, biogas contains around $50\\mathrm{-}70~\\%$ methane and $30\\text{\\textperthousand}$ carbon dioxide (Xie et al., 2020), although the exact composition can vary depending on the specific conditions. Under the right conditions, the biogas can be subsided on a designated substrate to produce a deposition carbon layer known as Bio-Graphene.  \n\nThe Bio-Graphene growth during carbon deposition plays an important role in the fabrication process. Thus, optimizing the growing environments is crucial to obtaining appropriate deposition and exfoli­ ation. Alumina boat configuration is utilized to adjust the growth con­ ditions, allowing for the regulation of gaseous compound release and enhancing gas flow. When thermal pressure is issued on the OPS bio­ char, it releases certain gaseous compounds when interacting with the dissociative substrate surface will deposit carbon and produce pores within the deposited layer (Serykh & Agafonov, 2020). To achieve the formation of the carbon-based nanomaterial, it is necessary to subject the carbon layer to high temperatures. This can be accomplished by creating a high-temperature environment, which will promote the development of carbon deposition and exfoliation during the Chemical Vapor Deposition (CVD) process.  \n\nBiomass from oil palm waste has been used over the years as a pre­ cursor due to its abundance of carbon content potential to fabricate graphene and graphene-like material (Safian et al., 2021). This research aims to investigate OPS green biomass precursor usage in fabricating Bio-Graphene instead of relying on factory-manufactured graphite pre­ cursor. The OPS is pyrolyzed to produce rich-methane potential carbon precursor and Bio-Graphene is fabricated in two different controlled settings/alumina boat placement during the CVD process. The produced the carbon-based nanomaterial was characterized using various analytical techniques, including Field Emission Scanning Electron Mi­ croscopy, Atomic Force Microscopy, Raman Spectroscopy, X-ray diffraction, and I-V measurement. According to the results, the use of better-closed settings (ABC-2) led to the growth of high-quality BioGraphene with improved crystallinity, detectable growth spurt, esti­ mated few-layer thickness, larger growth area, and lower surface roughness.  \n\nThis study presents a novel and sustainable method for producing direct deposition Bio-Graphene using OPS biochar as the precursor material. The process involves subjecting OPS biochar to a heating process to release gaseous compounds that are then deposited onto a substrate using CVD. Due to the new and unique low-cost CVD technique incorporated in this research, detailed information on the growing environment—whether partial or total cover— is lacking, which is imperative for the synthesis process. This research focuses on mecha­ nistic insight into how different growing environments influence or restrict the CVD deposition process, distinguishing it from other CVD research. The future application of this research could be in the pro­ duction of cost-effective and sustainable carbon-based nanomaterial for various industrial applications Furthermore, this study opens an array of methane-to-carbon-based nanomaterial possibilities from biomass sources instead of relying solely on industrialized methane containers. This approach presents a more sustainable and environmentally friendly method of producing carbon-based nanomaterial.  \n\nThe issue of CVD graphene growth can be observed from the para­ digm of economic comparative analysis between traditional CVD and this research CVD. Tradition CVD often possesses a few characteristics aspect such as normal atmospheric pressure, gaseous exposure, chemical vapours, surface reaction/decomposition, and thin layer formation (Dobrzanski et al., 2013). Although this research borrowed various key aspects from traditional CVD, the gas source during gaseous exposure sequences has been changed. In usual case, expensive methane and other gases are employed in their pure form, directed towards the CVD chamber for graphene growth. To add context, pure methane is sold around the world averages at 1.1 USD/litre, according to Global Petrol Prices. CVD process cost can be significantly reduced by employing green precursor as their gas source. However, this in turn creates a drawback, where the small gaseous release from green precursor might not accommodate well towards a large chamber from traditional CVD. Thus, employing two distinct growing environments to properly accommodate green precursors can create an overall cost reduction in the operation.",
        "category": " Introduction"
    },
    {
        "id": 7,
        "chunk": "# 2. Materials and methods",
        "category": " Materials and methods"
    },
    {
        "id": 8,
        "chunk": "# 2.1. Raw materials  \n\nThe raw materials for palm oil waste were obtained from United Oil Palm Industries Sdn. Bhd. in Nibong Tebal, Penang, Malaysia, consisting of palm oil waste, specifically Oil Palm Shell (OPS). OPS is collected fresh from the mill and to ensure its shelf life and quality, the palm oil waste was subsequently kept in a dark area to avoid spoilage and contamination from fungi and other microorganisms. Subsequently, palm oil waste requires multiple processes to prepare it as a precursor. The palm oil waste is grounded and screened to obtain uniform particle size, afterward dried in a Force Air Convention Oven (Venticell Oven) at $105^{\\circ}\\mathrm{C}$ for $24\\mathrm{~h~}$ to ensure moisture escaped from the palm oil waste. Now, OPS is ready to be used as a precursor for biochar production.",
        "category": " Materials and methods"
    },
    {
        "id": 9,
        "chunk": "# 2.2. Production of biochar  \n\nThe prepared OPS palm oil waste is utilized as a precursor to produce biochar. This process involved multiple steps to ensure the quality and integrity of the product. The process starts with placing $200~\\mathrm{g}$ of OPS stainless steel pyrolizer and subsequently initiating pyrolysis process. The pyrolization process takes place in a compact muffle furnace suit­ able for high-temperature pyrolysis. The compact muffle furnace tem­ perature is raised gradually to $400~^{\\circ}\\mathrm{C}$ and held for $^\\textrm{\\scriptsize1h}$ . The entire pyrolization process is monitored using $\\mathrm{~K~}$ -type thermocouple that is placed inside the pyrolizer to ensure temperature accuracy. Throughout the entire process, nitrogen gas $\\left(\\Nu_{2}\\right)$ is used to purge air from inside the pyrolizer at a rate of $500~\\mathrm{mL/min}$ .",
        "category": " Materials and methods"
    },
    {
        "id": 10,
        "chunk": "# 2.3. Preparation of zinc Chloride-Silicon wafer  \n\nThe preparation for the graphene growth template involved a few steps to ensure its readiness for subsequent graphene synthesis. The template is made from a silicon wafer disc that is cut to $_{1\\thinspace\\mathrm{cm}\\mathrm{x}1}$ cm using a diamond cutter. After the cutting process, each silicon wafer was cleaned and dried in the Force Air Convention Oven for $^\\textrm{\\scriptsize1h}$ . Subse­ quently, the production of $\\mathrm{ZnCl}_{2}$ solution with a molarity of $\\approx0.4\\mathrm{{M}}$ is produced. The $0.4\\mathrm{~M~ZnCl_{2}}$ solution produced is airbrushed onto the cleaned silicon wafer with $15\\ \\mathrm{cm}$ between the two. Finally, the silicon wafer silicon wafer coated with a layer of $\\mathrm{ZnCl}_{2}$ is dried in a Drying Oven (Drying Oven Memmert UNB-500) at $105^{\\circ}\\mathrm{C}$ for $^\\textrm{\\scriptsize1h}$ to produce $\\mathrm{ZnCl}_{2}$ - Silicon Wafer (ZnSw), ready to be used as graphene growth template for",
        "category": " Materials and methods"
    },
    {
        "id": 11,
        "chunk": "# CVD.",
        "category": " Materials and methods"
    },
    {
        "id": 12,
        "chunk": "# 2.4. Chemical Vapor deposition Procedure  \n\nA tubular quartz tube with a length of $124\\mathrm{cm}$ , an internal diameter of $6.9\\mathrm{cm}$ , and an outer diameter of $7.5\\mathrm{cm}$ is placed in a Heating Furnace (Naber-Labortherm R70/9 Furnace). (ABC-1) The biochar produced and ZnSw is placed in an alumina boat with a length of $10.0\\mathrm{cm}_{\\mathrm{i}}$ , a height of $1.8\\mathrm{cm}$ , and a width of $4.0\\mathrm{cm}$ , then two different alumina boats with (i) a length of $5.0\\mathrm{cm}$ , a height of $2.0\\mathrm{cm}$ and width of $2.0\\mathrm{cm}$ and (ii) with a length of $5.0\\mathrm{cm}$ , a height of $0.5\\mathrm{cm}$ and width of $1.0\\mathrm{cm}$ is placed in a position to cover the biochar and ZnSw. The temperature of the furnace is raised to $900^{\\circ}\\mathrm{C}$ , the heating rate of $10\\mathrm{^{\\circ}C/m i n}$ , and the residence time of $35\\mathrm{min}$ . Nitrogen gas $\\left(\\Nu_{2}\\right)$ was used as an inert gas to purge air from inside the pyrolizer at $500\\mathrm{mL/min}$ ; the purging was continued from the start of the process until the pyrolizer is cooled down. (ABC-2) Continuing the experiment, different placement of alumina boat was done, as the biochar produced and ZnSw is placed in an alumina boat with a length of $9.0\\mathrm{cm}$ , a height of $1.5\\mathrm{cm}$ , and width of $1.0\\mathrm{cm}$ , then a similar-sized alumina boat was placed on top. The same heating pa­ rameters are done on ABC-2. In Fig. 1, two different configurations of the alumina boat, namely ABC-1 and ABC-2, are presented. After conducting the experiments, the resulting samples obtained from both boat con­ figurations were analyzed and compared.",
        "category": " Materials and methods"
    },
    {
        "id": 13,
        "chunk": "# 3. Results and discussion",
        "category": " Results and discussion"
    },
    {
        "id": 14,
        "chunk": "# 3.1. Growth mechanism  \n\nThe growth mechanism occurs during the CVD process, whereas the action compromises multiple steps for Bio-Graphene deposition. The first is, the thermal breakdown of biochar and gaseous compound release (He et al., 2018). Thermal pressure at $900^{\\circ}\\mathrm{C}$ is applied to the alumina boat and biochar gains higher kinetic energy. The increase in kinetic energy results in the breakdown of biochar, resulting in various gaseous releases including methane $\\mathrm{(CH}_{4}\\mathrm{)}$ , carbon dioxide $\\left(\\mathrm{CO_{2}}\\right)$ , and other volatile gases (Abhijeet et al., 2019). The gaseous release that occurs during this step is due to carbon-containing bonds in the biochar decomposition.  \n\nThe second step involves methane decomposition into the carbon layer. $\\mathrm{CH}_{4}$ , which is the main gaseous compound produced from the previous step plays a vital role for carbon deposition. In the hightemperature CVD environment, $\\mathrm{CH}_{4}$ acquires sufficient energy to un­ dergo thermal decomposition into elements of carbon and hydrogen gas. The carbon in this case deposits itself onto the substrate forming a layer. On the other hand, hydrogen gaseous remains stagnant around the CVD environment growth for a while and subsequently flows out with the nitrogen-supplied gas. The carbon layer is an important part of the experiment to finalize the graphene growth.  \n\nDuring these two steps, another reaction happen which is the decomposition of zinc chloride $\\mathrm{(ZnCl_{2})}$ . This is the third step that simultaneously occur with the previous two mentioned steps. As the temperature increases within the CVD environment, beyond its boiling point the compound begins to decompose into zinc crystal and chloride gas. The chloride gas escapes the tubular furnace, while the zinc crystal deposits onto the silicon wafer. The zinc becomes an active part during the redox reaction that will occur subsequently.  \n\nIn the fourth step, $\\mathsf{C O}_{2}$ is procured in the second step, and zinc crystals obtained in the third step react with each other. This reaction is critical to the CVD process because it forms zinc oxide (ZnO) and carbon monoxide (CO). In this reaction, zinc crystal absorbs one oxygen molecule from $\\mathsf{C O}_{2},$ producing the compound $z_{\\mathrm{{nO}}}$ and gas by-product, CO (Lu et al., 2018). The $z_{\\mathrm{{nO}}}$ is responsible for converting the carbon layer produced during the first step into graphitic-nature carbon.  \n\nThis results in the last step which is porous activity. The carbon layer deposited in the first step interacts with $z_{\\mathrm{{nO}}}$ produced in the fourth step in order to create a porous layer, in turn graphitic-nature layer. The carbon element absorbs one oxygen from the $z_{\\mathrm{{nO}}}$ to produce zinc crystals and carbon monoxide. This zinc crystal can continue partici­ pating in further reactions, and the carbon monoxide escapes the tubular furnace as a gas. The continuous cycling of these reactions contributes to the formation of pores in the material.",
        "category": " Results and discussion"
    },
    {
        "id": 15,
        "chunk": "# 3.2. Characterization of bio-graphene  \n\nField Emission Scanning Electron Microscopy (FESEM) was con­ ducted on the fabricated Bio-Graphene samples to observe their surface structure. In terms of morphology, FESEM was performed on the fabri­ cated carbon-based nanomaterial, labeled ABC-1 and ABC-2, based on their respective settings. ABC-1 exhibited an agglomeration of mostly bonded particles with some minor segregation and a round-to-oval pattern, while ABC-2 showed an uneven layered growth and partial exfoliation at the base. ABC-1 had a more planar surface compared to ABC-2, which had a higher carbon deposition.  \n\nThe FESEM can detect the presence of a carbon layer on the substrate after fabrication. Both samples exhibited the presence of carbon on the substrate, thus indicating the success of the novel fabrication process. Two types of Bio-Graphene were produced, labeled ABC-1 and ABC-2, based on their respective settings and alumina boat placement. The FESEM analysis of ABC-1 showed an agglomeration of mostly bonded particles, with some particles showing minor segregation and a roundto-oval pattern. The surface presents a relatively uniform and smooth texture, indicating a smooth morphological structure without significant agglomeration (Fig. 2(a)). In contrast, ABC-2 showed an uneven layered growth and higher carbon deposition. The ‘splotches’ graphene struc­ ture indicates the presence of a thicker carbon layer with a higher possibility of surface defects. ABC-2 overall morphology is less uniform than ABC-1, with a rougher exterior structure. Despite these differences, both ABC-1 and ABC-2 exhibited close-bonded carbon structure and layering in the FESEM analysis. Comparing the FESEM results obtained in this study to previous research that uses pure methane to fabricate graphene, shows similarities between them. Both products have planar characteristics with a tendency to agglomerate, forming a cohesive layer. Both products also show the trend of carbon deposition increment as the volume of methane increases (Selvakumar et al., 2016). It is speculated that ABC-2 has a higher chance of methane-to-substrate contact due to its configuration, which involves a total cover alumina boat.  \n\n![](images/af1bd090201fed749fa2310761762a33c83d9e401031b865431fae205adf62cb.jpg)  \nFig. 1. Placement of Alumina Boat for ABC-1 and ABC-2.  \n\n![](images/4efcd02e8bdc7cdfd30da54f934eabb19250766c5edb1af48948d34d6de0b479.jpg)  \nFig. 2. (a) FESEM image of ABC-1, (b) FESEM image of ABC-2, (c) AFM 3D Image for ABC-1 and (d) AFM 3D Image for ABC-2 ${\\bf{\\{n=1\\}}}$ samples each)  \n\nAtomic Force Microscopy (AFM) 3D imaging and root mean square (RMS) surface roughness were used to further observe the surface morphology of ABC-1 and ABC-2. According to the 3D images in Fig. 2 (c,d), ABC-1 had a more even surface for the Bio-Graphene compared to ABC-2, which displays a less planar surface. This is due to the higher chance of methane to substrate contact for ABC-2 which promotes better carbon deposition. Additionally, AFM shows that the surface roughness of ABC-1 was also found to be lower than that of ABC-2, as shown in Table 1. A lower surface roughness indicates a more uniform carbonbased nanomaterial layer (Salifairus et al., 2018). Previous studies have reported similar trends in AFM surface roughness of selected samples indicating that those with the lowest surface roughness values are more likely to have a planar structure of graphene (Mesˇkinis et al., 2022). According to mechanistic observation by FESEM and AFM, ABC  \n\nTable 1 AFM Surface Roughness and Thickness for ABC-1 and ABC2.   \n\n\n<html><body><table><tr><td>Sample</td><td>Surface Roughness (nm)</td></tr><tr><td>ABC-1</td><td>40.3</td></tr><tr><td>ABC-2</td><td>55.9</td></tr></table></body></html>  \n\n1 morphology indicates areas that could potentially be multi-layer graphene under smoother and more uniform surfaces but with higher roughness and significant peak formations. On the other hand, ABC-2 demonstrates graphene with a less pronounced layer, possessing a higher irregular surface (possible defect) but more evenly distributed surface morphology.  \n\nFor the internal structure of graphene, Raman is done on fabricated Bio-Graphene by observing the vibrational energy modes. Both samples possess the G, D, and 2D bands that arise from the graphitic structure and $\\mathsf{s p}^{2}$ layer of hybridization (Safian et al., 2021). The G band corre­ sponds to the $\\mathbf{E}_{2g}$ phonon of the $\\displaystyle\\mathsf{s p}^{2}$ carbon atom, while the D band corresponds to the breathing mode of k-point phonons of $\\mathbf{A}_{1g}$ symmetry at the vibration of the atom in planar termination of irregular graphite (Widiatmoko et al., 2019). ABC-2 has a higher and observable G and D band than ABC-1. ABC-2 having stronger signals than ABC-1 indicates that ABC-2 carbon-based nanomaterial has a smaller crystalline size (Nasir et al., 2019). G and D bands of ABC-1 were observed to be 1602 and $1334\\mathrm{cm}^{-1}$ , respectively in Fig. 3. Whereas the G band and D band of  \n\n![](images/88dc0d2266598c192e6f8658f07a31bc6ec3126eb15b775ecf04a2ecfd3b86e0.jpg)  \nFig. 3. Raman Graphical for ABC-1 and ABC-2 ( ${\\bf{\\dot{n}}}=1$ samples each).  \n\nABC-2 were observed to be 1583 and $1330\\mathrm{cm}^{-1}$ , respectively. Previous work employed CVD to create Bio-Graphene layers by using Palm Oil Waste as precursor biomass. The previous results showed similar MicroRaman mapping located around the same area as this paper’s result (Salifairus et al., 2016). The G and D band ratio intensity presents the quality of the carbon-based nanomaterial produced. As seen in Table 2, their ratio intensity is $\\mathrm{I_{G}}/\\mathrm{I_{D}}=1.2$ for ABC-1 and $\\mathrm{I_{G}/I_{D}}=0.7$ for ABC-2. ABC-2 possesses a lower ratio intensity than ABC-1 despite having higher and observable G and D bands. This indicates that ABC-2 has a lower degree of graphitization than ABC-1 (Amir Faiz et al., 2020). An additional ${\\bf D}^{\\prime}$ band peak can be seen at $1603\\mathrm{cm}^{-1}$ . Defectiveness within the structure causes the G band to broaden which creates a D’ band peak (Kaniyoor & Ramaprabhu, 2012). The RAMAN analysis results are further solidified when compared to FESEM results. During morpho­ logical observation, ABC-2 is suspected to possess a higher level of defect compared to ABC-1 due to its presence of a thicker carbon layer. This coincides with RAMAN analysis showing a more prominent D band (defect band) for ABC-2.  \n\n2D band is the secondary peak of D band. High 2D band is associated with single layer graphene and low 2D band is associated with multi­ layer graphene. As seen in Table 2, their ratio intensity is $\\mathrm{I_{2D}/I_{G}}=0.7$ for ABC-1 and $\\mathrm{I_{2D}/I_{G}}=0.6$ for ABC-2. The 2D and G band ratio intensity band indicates the number of layers within graphene structure. The $\\mathrm{I_{2D}/}$ $\\mathrm{I_{G}}$ value less than 1 indicates 3 or more-layer graphene (Castriota et al., 2019). However, in some cases of $\\mathrm{I_{2D}/I_{G}}$ values between 0.3 and 0.8, the graphene can be treated as 2–3 layers of graphene (Akhavan et al., 2014). The number of layers of Bio-Graphene indicates two to three graphene layers for ABC-1 and ABC-2. The result is an improvement from Robaiah Hj Mamat in 2018 which also uses palm oil waste to create graphene through CVD which $\\mathrm{I_{2D}/I_{G}}$ value was 0.3 (Mamat et al., 2018). ABC-1 and ABC-2 analyzed 2D bands that possessed shortcomings due to their peak position. Typical single-layer graphene is around $2700\\mathrm{cm}^{-1}$ while both samples (ABC-1, ABC-2) have shifted away from the value, indication strain, and defect. Although ABC-1 indicates lower defect and graphene layer, the peak prominence highly favours ABC-2 suggesting higher graphene deposition on the substrate. This, in turn, results in a higher product-to-raw-material ratio.  \n\nTable 2 Micro-Raman value of D, G and 2D for ABC-1 and ABC-2.   \n\n\n<html><body><table><tr><td>Sample</td><td>G-Band (cm-1)</td><td>D-Band (cm-1)</td><td>2D-Band (cm-1)</td><td>IG/ID</td><td>I2D/IG</td></tr><tr><td>ABC-1</td><td>1602</td><td>1334</td><td>2844</td><td>1.2</td><td>0.7</td></tr><tr><td>ABC-2</td><td>1583</td><td>1330</td><td>2656</td><td>0.7</td><td>0.6</td></tr></table></body></html>  \n\nFor the crystalline structure of graphene, XRD is done on fabricated Bio-Graphene by observing the peak position. ABC-1 and ABC-2 are done for XRD spectra in the range of 2θ from 10 to $60^{\\circ}$ as shown in Fig. 4. XRD results have high noise signal from low nucleation of the carbonbased nanomaterial on a silicon wafer and create difficulty in detect­ ing formation (Holder & Schaak, 2019). The best estimation was given due to the high noise. Moreover, it can be observed that there are no discernible peaks at $2\\uptheta=42.8^{\\circ}$ , which is associated with a graphene crystalline peak at (0 0 2). The possibility for this occurrence is due to: (i) high noise-to-signal ratio or (ii) short-range order in stacked BioGraphene layers (Stobinski et al., 2014).  \n\nFurthermore, both XRD diffraction peaks are quite low indicating Bio-Graphene produced has a structure between the crystalline and amorphous structures. The broadness of both samples suggests that there were more oxygen-containing groups on the edges of each layer (Yang et al., 2020). From the observed peak broadening, it is inferred that the stacking of the carbon-based nanomaterial is not well-ordered due to incomplete exfoliation (Lee et al., 2019). There is an indication of the crystalline peak at (0 0 2) with a diffraction peak at $2\\uptheta=21.48^{\\circ}$ for ABC-1 and $2\\uptheta=22.8^{\\circ}$ for ABC-2 as seen in Fig. 4. The prominent graphene peak around $2\\theta\\:=\\:25{-27^{\\circ}}$ is absent indicating amorphic structure diverting away from graphitic lattice structure. Broad peaks on both samples indicated that it is not highly crystalline likely to have defects, multi-layer structure, and disordered carbon structure. How­ ever, ABC-2 possessed a higher intensity than ABC-1, suggesting a more ordered carbon structure and higher graphene content. The XRD anal­ ysis results are further cemented when compared to FESEM and RAMAN results indicating that both samples indeed possessed levels of defect.  \n\nBy using Bragg’s Equation to the (0 0 2), intercellular spacing can be obtained. The intercellular spacing of ABC-1 and ABC-2 is $0.4~\\mathrm{{nm}}$ and $0.4~\\mathrm{{nm}}$ , respectively. On the other hand, by using Scherrer’s equation and the constant value 0.9 from the (0 0 2) reflection, the crystalline size for ABC-1 and ABC-2 is $2.4\\ \\mathrm{nm}$ and $2.0\\ \\mathrm{nm}$ , respectively as seen in Table 3 (Stobinski et al., 2014). Thus, ABC-2 has a smaller crystalline size than ABC-1.  \n\nThe IV measurement is conducted on ABC-1, ABC-2, and silicon wafers. Alumina adheres to the surface of ABC-1, ABC-2, and silicon wafers. For ABC-1 and ABC-2, alumina covered the Bio-Graphene deposited onto the silicon wafer. The results show the IV measurement of ABC-1 is $150\\Omega$ , while ABC-2 had a resistance of $112.5\\Omega$ . On the other hand, the silicon wafer has the highest resistance at $387.5\\Omega$ . As seen in  \n\n![](images/5a5554d39c10604d1c3b9be92980eb1348bda0c988b71f36dd98f78a41c1f5e0.jpg)  \nFig. 4. XRD for ABC-1 and ABC-2 $\\mathbf{\\tilde{n}}=1$ samples each).  \n\nTable 3 Structural parameters of ABC-1 and ABC-2 resulting from the XRD patterns.   \n\n\n<html><body><table><tr><td>Sample</td><td colspan=\"2\">Peak (002)</td><td></td><td></td><td></td></tr><tr><td></td><td>20 (deg)</td><td>FWHM (deg)</td><td>Crystalline Size (nm)</td><td>Intercellular Spacing (nm)</td><td>Graphene Layers Number</td></tr><tr><td>ABC-1</td><td>21.5</td><td>3.3</td><td>2.4</td><td>0.4</td><td>8</td></tr><tr><td>ABC-2</td><td>22.8</td><td>3.9</td><td>2.0</td><td>0.4</td><td>7</td></tr></table></body></html>  \n\n![](images/416903f9204a7ec22515e094d1cd1503213f9dfcb1cf0c0182dcc5c7ad28c0c8.jpg)  \nFig. 5. I-V Curve for Silicon Wafer, ABC-1 and ABC-2 ${\\bf{\\hat{n}}}=1$ samples each).  \n\nFig. 5, the slope is greater for the two carbon-based nanomaterials deposited onto the silicon wafer samples compared to the silicon wafer indicating a lower resistivity to the former. This is due to the presence of Bio-Graphene that improves on the electron pathway which is attributed to its conducting properties (Mulla et al., 2023). When calculating the resistivity and conductivity of ABC-1 and ABC-2, it shows that ABC-1 has a higher resistivity and lower conductivity than ABC-2. ABC-1 resistivity and conductivity are $280.4\\Omega\\mathrm{m}$ and $3.6\\times10^{-5}\\mathrm{S/cm}.$ respectively, while resistivity and conductivity are 127.1 Ωm and $7.9\\times10^{-5}\\ \\mathrm{S/cm}$ . The difference in resistance between ABC-1 and ABC-2 is related to the quality of the carbon-based nanomaterial on the silicon wafer. This correlates with better quality graphene having higher structural lattice ordering which significantly enhances the graphene pathway to be less resistive and conduct more electricity (Yildiz et al., 2021).  \n\nXPS provides a comprehensive analysis of chemical composition that provides a thorough insight into the entirety of the produced BioGraphene framework. The evaluation presents unique spectra peaks that correlate to individualized core-level electrons of the atom’s bind­ ing energy. This determines the specialized atomic elements of the carbon-based nanomaterial, in this case consisting of $\\mathbf{C}_{1s},$ $\\mathrm{O}_{1s}$ , $\\mathrm{Si}_{2s_{:}}$ , and $\\sin_{2\\mathrm{p}}$ situated at $\\sim285\\mathrm{eV}$ , ${\\sim}531\\mathrm{eV}$ , ${\\sim}155\\mathrm{eV}$ , and $\\sim104\\mathrm{eV}$ (Keyn et al., 2021). The presence of $\\mathrm{Si}_{2s}$ and $\\sin_{\\mathrm{{}}}\\operatorname{si}_{2{\\mathrm{{p}}}}$ in Fig. 6 is due to the silicon wafer substrate, securing the deposited carbon-based nanomaterial layer. $\\mathbf{C}_{1s}$ presence at $\\sim285\\ \\mathrm{eV}$ confirms carbon species layering on the silicon wafer during CVD that consists of $\\mathsf{s p}^{2}$ carbon atoms in a graphitic structure. The peak at \\~ 531 eV appeared due to oxygen. The overall XPS spectra managed to capture ABC-2 molecular makeup that further validated the fabrication process, utilizing an alumina boat for gaseous capture on a silicon wafer for carbon layering.",
        "category": " Results and discussion"
    },
    {
        "id": 16,
        "chunk": "# 4. Conclusion  \n\nBio-Graphene is synthesized from OPS biomass via pyrolysis and  \n\n![](images/d76f0ef630ad534d41a6672a4f206add7589cf4c493761f905a8e40b24dea403.jpg)  \nFig. 6. Full XPS graph of the ABC-2 $\\mathbf{\\tilde{n}}=1$ samples each).  \n\nCVD. This method involves applying gaseous compounds from pyro­ lyzed OPS biochar directly onto a silicon wafer using two alumina boat configurations: ABC-1 and ABC-2. By bypassing etching and transfer steps, the characterization of carbon-based nanomaterial becomes easier. ABC-2 offers better encapsulation of gaseous compounds, leading to improved carbon deposition, higher nucleation, well-ordered struc­ ture, reduced graphitic layers, enhanced crystallinity, and higher con­ ductivity. This research demonstrates the potential of biomass-derived biogas in synthesizing eco-friendly carbon-based nanomaterial. Such advancements could replace methane-based graphene, enabling affordable, sustainable, and environmentally friendly production methods.",
        "category": " Conclusions"
    },
    {
        "id": 17,
        "chunk": "# CRediT authorship contribution statement  \n\nM.D. Nurhafizah: Conceptualization, Supervision, Funding acqui­ sition, Writing – original draft, Writing – review & editing. A.A. Azahar: Investigation, Methodology, Writing – original draft. N. Abdullah: Su­ pervision, Data curation.",
        "category": " Abstract"
    },
    {
        "id": 18,
        "chunk": "# Funding  \n\nThis work was supported by the Ministry of Higher Education Malaysia for Fundamental Research Grant Scheme (FRGS) with project code: FRGS/1/2019STG05/USM/02/7 and Research University Grant (RUI), Universiti Sains Malaysia with project code: 1001/PFIZIK/ 8011113.",
        "category": " References"
    },
    {
        "id": 19,
        "chunk": "# Declaration of competing interest  \n\nThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.",
        "category": " Conclusions"
    },
    {
        "id": 20,
        "chunk": "# Acknowledgements  \n\nA special thanks to the Ministry of Higher Education Malaysia for the Fundamental Research Grant Scheme (FRGS) with project code: FRGS/ 1/2019STG05/USM/02/7 and Research University Grant (RUI), Uni­ versiti Sains Malaysia with project code:1001/PFIZIK/8011113 for the financial supports. The authors also want to express their gratitude to Energy Lab, School of Physics, Universiti Sains Malaysia for the statistics information provided.",
        "category": " Acknowledgements"
    },
    {
        "id": 21,
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