Polymeric Synthesis of Metallic Oxide Nanocomposite in the Presence of Rare Earth for their Water-Splitting Applications

215 DOI: Availability Annual Methodological Archive Research Review http://amresearchreview.com/index.php/Journal/about 1Aqsa Ayyoub, 2Prof. Dr. Zahida Batool Polymeric Synthesis of Metallic Oxide Nanocomposite in the Presence of Rare Earth for their Water-Splitting Applications Article Details ABSTRACT Aqsa Ayyoub Department of Physics - The Islamia University of Bahawalpur, Pakistan, Corresponding Author, aqsa1409[email protected]om Prof. Dr. Zahida Batool Department of Physics - The Islamia University of Bahawalpur, Pakistan, zahida.batoo[email protected]k The production of hydrogen and oxygen from water, driven by solar energy through photoelectrochemical and electrocatalysis processes, represents a promising avenue toward clean fuel generation. This study focuses on the synthesis and comprehensive characterization of Bismuth oxide-based nanocomposites, specifically Bi2O3/NiO, Bi2O3/NiO/CeO2, and Bi2O3/NiO/CeO2/PVP, using the Sol-gel method. To evaluate the synthesized nanocomposites, a diverse array of characterization techniques were employed, including X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), cyclic voltammetry (CV), and Scanning Electron Microscopy (SEM). The XRD patterns confirmed the formation of Bi2O3/NiO, Bi2O3/NiO/CeO2, and Bi2O3/NiO/CeO2/PVP nanocomposites, exhibiting a cubic crystalline structure. Crystallite size and lattice strain were meticulously determined using the Scherrer formula, Williamson-Hall, and Scherrer plot methods, revealing average crystallite sizes of 15.41 nm, 13.64 nm, and 15.01 nm, respectively. SEM was used to determine the surface morphology and particle distribution. Furthermore, cyclic voltammetry was employed to ascertain the electrochemical performance of the Bi2O3/NiO/CeO2/PVP nanocomposites. Our findings indicate that Sol-gel synthesized Bi2O3/NiO, Bi2O3/NiO/CeO2 and Bi2O3/NiO/CeO2/PVP composites exhibit promising characteristics for water splitting applications. Through extensive electrochemical testing, including CV, LSV, and EIS, we observed that these prepared nanocomposites exhibit higher current densities of 10 mAcm-2 at significantly lower over potential (190 mV and 25.7 mV vs RHE) and smaller Tafel slopes (88.3 mVdec-1 and 261 mVdec-1 ) in the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) compared to other composite materials. Additionally, electrochemical impedance measurements indicated that the resistance of the modified electrode and the bare electrode ranged from 0 to 160 Ω. These results collectively demonstrate the promising potential of Bi2O3/NiO-based nanocomposites as efficient catalysts for sustainable water-splitting processes. http://amresearchreview.com/index.php/Journal/a bout Online ISSN Print ISSN 3007-3197 3007-3189 Annual Methodological Archive Research Review 216 INTRODUCTION There are many common issues all around the world. Among these issues, a few issues are very important. These are energy production and storage and environmental pollution. Researchers are continuously working their efforts to address these issues. The use of fossil fuels for energy production and preservation is one solution to energy shortages that has gained widespread recognition (Chaudhary, Basha et al. 2023). On the other hand, when fossil fuels are burned, they give off harmful gases that contribute directly to pollution and, in the long run, global warming (Yue, Lambert et al. 2021). Because of this, it is crucial to phase out fossil fuels in favor of renewable energy sources that are better for the environment (Tahir, Chaudhary et al. 2022). Hydrogen is a great choice for making energy in the future because it is light and has a high energy density (Yousaf, Katubi et al. 2023). Hydrogen can be made in several different ways, such as by electrolyzing or photolyzing water, reforming biomass, or burning fossil fuels (Hassan, Baig et al. 2023). Most hydrogen is made through a process called electrolysis (Osgood, Devaguptapu et al. 2016). In electrochemical water-splitting reactions, at the cathode, the HER takes while the OER takes place at the anode. Among the issues, electrocatalytic water-splitting has drawn a lot of interest due to its inexpensive, high efficiency, and low power threshold. Since the OER has slow rate kinetics and requires a high energy barrier to generate the reaction, it needs a very large overpotential and is inefficient (Wang, Lu et al. 2021). The HER process has been observed to have a faster rate of kinetics and require very low overpotential (Stühmeier, Pietsch et al. 2021). Materials based on noble metals, such as ruthenium and iridium oxides for the oxygen evolution reaction and platinum for the hydrogen evolution reaction, exhibit impressive water-splitting efficiency, but they are not practical for widespread use due to their scarcity, high cost, and short longevity (Liu, Ma et al. 2021). Therefore, in the last few decades, there has been a lot of focus on developing and manufacturing electrocatalysts that are highly efficient, extremely accessible, and very cheap for high-efficiency water splitting. In particular, oxides, chalcogenides, phosphides, and metal-organic frameworks (MOFs) based on transition metals have gained popularity due to their superior performances and extended durability (Liu, Guo et al. 2023). Since the above-discussed state-of-the-art electrocatalysts only show performance in one of these areas, it is both difficult and exciting to design a dual functional catalyst that can concurrently catalyze both hydrogen evolution and oxygen evolution reactions. Among the compounds, Bi2O3has attracted significant interest due to its unique crystal structures with various probable modifications and band gaps in the desired range (Wang, Paik Annual Methodological Archive Research Review 217 et al. 2015). Bi2O3mainly has four polymorphs, including the monoclinic (α), tetragonal (β), body-centered cubic (γ), and face-centered (δ) phases. Among these, narrow band gaps of 2.8 and 2.48 eV for α-Bi2O3and β-Bi2O3, respectively, have been reported in most experimental studies out of which β-Bi2O3has been well known to exhibit superior photocatalytic activity under visible light illumination (Li, Li et al. 2014). The nickel oxide hydroxide (Ni2O2(OH)) as an electrocatalyst for water splitting has also received significant attention due to its material potential. There is a lot of surface area available for electrocatalytic reactions on Ni2O2(OH) because of its layered structure. Their electrocatalytic activity and efficiency for water-splitting reactions, especially the OER, are improved as a result of the layered structure. The OER reaction is an essential part of the water-splitting reaction, but it is a difficult reaction that calls for a lot of overpotentials to be active. Ni2O2(OH) are easy to synthesize, abundant, and inexpensive, making them preferable over electrocatalysts based on precious metals like platinum for use in large-scale applications. Ni2O2(OH) activity for the HER is comparable to that of Ni(OH)2and NiO(OH), but lower than that of some other electrocatalysts [29,30]. Researchers have attempted a variety of methods, including doping with other metals and integrating them into composite materials with other materials like carbon nanotubes (CNTs), to increase their activity for HER (Afaq, BaQais et al. 2024). EXPERIMENTAL SECTION MATERIAL CHARACTERISTICS Bismuth nitrate pentahydrate, nickel nitrate pentahydrate, cerium nitrate hexahydrate, and polyvinylpyrrolidone (PVP) were used to synthesize the nanocomposite, NaOH as a pHcontrolling agent, and dimethyl sulfoxide (DMSO) was used as a solvent. Sigma Aldrich provided the materials and chemicals used in the synthesis technique. Throughout the trial, distilled water and ethanol were utilized for washing purposes. TABLE 1: DETAILS OF CHEMICAL USED IN NANOCOMPOSITE SYNTHESIS Sr. No. Chemicals Chemical formula Molecular weight (g/mol) 1 Bismuth nitrate pentahydrate Bi (NO3)3. 5H2O 485.07 2 Nickel nitrate pentahydrate Ni(NO3)2.5H2O 290.80 3 Cerium nitrate hexahydrate Ce(NO3)3.6H2O 434.22 4 Polyvinylpyrrolidone PVP 111.14 Annual Methodological Archive Research Review 218 5 Dimethyl sulfoxide C2H6OS 78.13 6 Ethanol C₂H₆O 46.07 7 Sodium hydroxide NaOH 39.997 SYNTHESIS OF BI2O3/NIO COMPOSITE 2.6 grams of bismuth nitrate pent hydrate has been added to a 100 ml beaker containing 30 ml DMSO to create a Bi2O3/NiO nanocomposite. Placing the beaker on a hot plate, start stirring with a magnetic stirrer, and then take the beaker off the hot plate after around two hours. To maintain pressure on the beaker, aluminum foil was being employed. Until all of the Bi (NO3)3. 5H2O has been dissolved, the solution is continuously stirred. Finally, a pale golden hue was achieved (Jiang and Wang 2016) . After that, a 100 ml beaker containing 30 ml of DMSO was filled with 0.42g of nickel nitrate pentahydrate. With the beaker on a hot plate, start stirring for around two hours at an ambient temperature of 70 °C using a magnetic stirrer. Sodium hydroxide, also known as NaOH, helped 2.6 g of Bismuth nitrate 30 ml DMSO Bi2O3NPs Wash and dried at 50°C Heated at 300°C in oven Heated at 70°C Figure 4. 1: Flow chart of Bi2O337 to maintain the PH. Until all of the Ni (NO3)2.5H2O has been completely dissipated in the solution, the solution is continuously stirred. Finally, the color black was attained. Now for making nanocomposites of Bi2O3/NiO, materials were dignified in Molar ratio (0.19M). Bismuth oxide and Nickel oxide powder was dissolved in 30 ml of DMSO separately. For an hour, the solution was agitated. Mix the nickel oxide and bismuth oxide solutions after an hour of stirring. Sodium hydroxide was employed to keep the pH between 9 and 10. The mixture was O.42 g of Nickel nitrate 30 ml DMSO Heated at 70°C NiO2NPs Wash and dried at 50°C Heated at 300°C in oven Figure 4. 3: Flow chart of NiO 38 stirred continuously to keep the temperature around 70 degrees Celsius. The precipitates were cooked in an oven at 180°C for two hours. Finally, a colored composite was produced. SYNTHESIS OF BI2O3/NIO/CEO2NANOCOMPOSITE 0.5 g of cerium nitrate hexahydrate was added to a 100 ml beaker with 10 ml of DMSO to create the Bi2O3/NiO/CeO2nanocomposite. Using a magnetic stirrer and a temperature of 50°C, place the beaker on a hot plate and start stirring. Sodium hydroxide was used to keep the PH constant. The mixture is continuously stirred until all of the Ce (NO3)3.6H2O has been dissolved. The precipitate was cooked in a furnace for two hours at 650 degrees Celsius. Finally, a rust-brown hue was achieved. Now, the components were determined in molar ratios to construct the nanocomposite of Bi2O3, NiO, and CeO2. Separately, 30 ml of DMSO was used to dissolve cerium Annual Methodological Archive Research Review 219 oxide, bismuth oxide solution, and nickel oxide solution. For an hour, the solution was agitated. Mix the composite of nickel oxide, bismuth oxide, and cerium oxide after one hour of stirring. Sodium hydroxide was employed to keep the pH between 9 and 10. The mixture was stirred continuously to keep the temperature at 50°C. The precipitates were cooked in an oven at 180°C for two hours. Finally, a composite in the color black was produced. SYNTHESIS OF BI2O3/NIO/CEO2/PVP COMPOSITE Now, the solution of PVP (0.1g) within 20ml comprising dimethyl sulfoxide was added dropwise to the Bi2O3/NiO/CeO2solution to form the nanocomposite of Bi2O3/NiO/CeO2/PVP. For an hour, the solution was agitated. Sodium hydroxide was employed to keep the pH between 9 and 10. The mixture was stirred continuously to keep the temperature around 90 degrees Celsius. The precipitates were cooked for two hours at 180 degrees Celsius in the oven. Finally, a black nanocomposite was produced. RESULTS AND DISCUSSION XRD ANALYSIS Phase identification and crystal structure of the Bi2O3, NiO, CeO2, Bi2O3/NiO, Bi2O3/NiO/CeO2, and Bi2O3/NiO/CeO2/PVP nanocomposites were investigated using an X-ray diffractometer with a range of 10° to 70° and CuKαradiations [1.5406Å]. The XRD data was examined using the Origin Pro. To investigate the NPs' hidden properties, many peaks were found and joined. Also utilizing the origin software, the peaks were labeled and marked. Once the structure of the synthesized substance was confirmed, the obtained data was compared with the peaks on the JCPDS card. The average crystalline size of synthesized samples was calculated using Debye Sherrer's formula applied to a few notable peaks (Imran, Batool et al. 2022). �= �� ����� → (4.1) Where the following elements are taken into account: D= which stands for the crystal's size; K= which represents the crystallite form factor with a defined value of 0.9; which stands for the CuKαradiation's wavelength; β= which stands for the full width at half maximum (measured in radians; and, which stands for the angle of diffraction. The interplanar gap is calculated using Bragg's formula: d = λ/ (2sinθ) Annual Methodological Archive Research Review 220 In this case, the letters d stand for the interplanar distance, for an incident X-ray wavelength, & for the Bragg's angle. Additionally, the following formula can be used to calculate dislocation density: ������������������= 1 �2 The variable D from the aforementioned equation stands for the crystal size. Using XRD data, this equation is used to determine the microstrain. The related Miller indices, FWHM, size of crystal, density of dislocation, & interplanar spacing of each sample are shown in the table that follows. We use the following formula, the amount of stress may be determined: ������=���� ���� →(4.5) To determine micro strain, apply the following relationship: �����������=����� 4→(4.6) Calculating the width of Bragg's peaks involves integrating sample impacts and measurements. ����=����������+�������������� → (�.�) Hence, �= �� �����→����= �� �(1 �)→ (4.9) An S.P has been drawn across 1/βand cosθ, as seen in Fig. 4.10, with 1/βalong the x-axis & cosθalong the y-axis. Data were linearly fitted, and the slope of the fitted line was used to determine the crystallite size. Annual Methodological Archive Research Review 221 FIGURE 1: XRD PATTERN OF BI2O3, NIO, CEO2, BI2O3/NIO, BI2O3/NIO/CEO2, AND BI2O3/NIO/CEO2/PVP NANOCOMPOSITES SEM ANALYSIS SEM ANALYSIS OF BI2O3NANOPARTICLES Results of the SEM investigation of the Bi2O3nanocomposite. The Bi2O3was produced as a lump of spherical particles (Chen, Hosseini et al. 2019). SEM ANALYSIS OF NIO NANOPARTICLES SEM images were used to analyze the surface morphology of NiO nanoparticles. The NiO SEM picture is seen in Figure. The items are small and collected, as can be observed, Spherical-shaped nanoparticles (Salavati-Niasari, Mir et al. 2010). SEM ANALYSIS OF CEO2NANOPARTICLES Using a Scanning Electron Microscope (SEM), nanoparticle morphology is discovered. In Figure Annual Methodological Archive Research Review 222 4.30, the SEM picture of the freshly generated cerium dioxide nanoparticles is shown. In the image, it can be observed that the bulk of particles are spherical. However, some of the elongated particles are also seen to be agglomerated (Kumar, Selvarajan et al. 2010). SEM ANALYSIS OF BI2O3/NIO NANOCOMPOSITES The morphology of artificial Bi2O3/NiO nanocomposites was studied using SEM. The Bi2O3was made from a mass of spherical particles at a magnification of 10.00K. For NiO, this image shows the particles are small and gathered into spherical nanoparticles. This demonstrates the presence of Bi2O3and NiO in our nanocomposite. SEM ANALYSIS OF BI2O3/NIO/CEO2NANOCOMPOSITES The morphology of artificial Bi2O3/NiO/CeO2nanocomposites was studied using SEM. The Bi2O3was made from a mass of spherical particles at a magnification of 10.00K. For NiO, this image shows the particles are small and gathered into spherical nanoparticles. For CeO2, the majority of the particles are spherical, as can be seen in Figure 4.32. But it's also noticeable that certain of the extended particles have gathered together. SEM ANALYSIS OF BI2O3/NIO/CEO2/PVP Nanocomposites the morphology of artificial Bi2O3/NiO/CeO2/PVP nanocomposites was studied using SEM. The Bi2O3was made from a mass of spherical particles at a magnification of 10.00K. For NiO, this image shows the particles are small and gathered into spherical nanoparticles. For CeO2, the majority of the particles are spherical. But it's also noticeable that certain of the extended particles have gathered together. The composite's morphology is altered by a polymer. Annual Methodological Archive Research Review 223 FIGURE 2: SEM IMAGE OF (A) BI2O3(B) NIO (C) CEO2(D) BI2O3/NIO (E) BI2O3/NIO/CEO2(F) Bi2O3/NiO/CeO2/PVP Annual Methodological Archive Research Review 230 evolution reaction (HER). FIGURE 8: LSV POLARIZATION OF HER OF BI2O3/NIO, BI2O3/NIO/CEO2, AND BI2O3/NIO/CEO2/PVP NANOCOMPOSITE CYCLIC VOLTAMMETRY (CV) I inserted the functioning electrode into the electrolyte solution and subsequently activated the system, thereby allowing the passage of electrical current through the electrode. As the current traversed the electrode, it generated a visual representation of the voltammogram on the computer screen. To observe the effects of varying scan rates, namely 20, 40, 60, 80, and 100 mV/s, I conducted this experiment. It was evident that the area encompassed by the voltammogram increased proportionally with the escalation of the scan rate. Consequently, I plotted the CV curves of Bi2O3/NiO, Bi2O3/NiO/CeO2, and Bi2O3/NiO/CeO2/PVP nanocomposites, employing the potential vs RHE on the x-axis and current density on the y-axis, at different scan rates. To determine the current density the following formula is used. ������� ������� (�) = ����(�) ����(�) (4.33) To find the potential over RHE following formula is used; ���� = ��������� + ���/���� + 0.059 ∗ ��. Where, E (Ag/AgCl) = observed potential Ag/AgCl = reference electrode. Annual Methodological Archive Research Review 231 FIGURE 9: CV CURVES OF BI2O3/NIO/CEO2/PVP NANOCOMPOSITE SAMPLE WITH INCREASING SCAN RATE FROM 20 TO 100 MV/S IN 1.0 M KOH ANALYZING THE ELECTROCHEMICAL SURFACE AREA (ECSA) The cyclic voltammogram of the fabricated Bi2O3/NiO, Bi2O3/NiO/CeO2, and Bi2O3/NiO/CeO2/PVP materials was recorded for the non-faradic region at various scan rates (mVs-1). The relationship between scan rate and current (A) was utilized to calculate the electrochemical surface area (ECSA) of the resulting samples, which is shown in Figure 5. The slope of these linear plots was considered as the double-layer capacitance (Cdl). The average Cdl values of Bi2O3/NiO, Bi2O3/NiO/CeO2, and Bi2O3/NiO/CeO2/PVP were determined to be 69, 2.35, and 4.6 mFcm-2, respectively. The higher average Cdl values of Bi2O3/NiO indicate a larger electroactive surface area for improved electrochemical performance. 104 To find the electrochemical Surface area (ECSA) formula = .Where Cs is the specific capacitance of the working electrode which is nickel foam and its specific capacitance is 40 μF/cm2 in 1M of KOH solution. Furthermore, the binary nanocomposite has greater available ECSA (1.725) as compared to its counterpart, which means it provides a highly porous shape and more exposed electroactive sites, which are responsible for excellent OER and HER performances. Annual Methodological Archive Research Review 232 FIGURE 10: GRAPH OF SYNTHESIZED BI2O3/NIO/CEO2/PVP NANOCOMPOSITE FOR DETERMINING ECSA ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS) For electrochemical impedance spectroscopy, an initial step involved the preparation of a 1M potassium hydroxide (KOH) solution. Subsequently, the working electrode was immersed into the aforementioned solution, and the system was activated by applying a potential window of approximately 0.5 V. The impedance graph of Bi2O3/NiO/CeO2/PVP reveals that the commencement of the semicircular curve indicates the presence of unbounded charged particles, thereby signifying a reduced resistance against the unrestricted motion of these charged particles. The impedance graph of my sample Bi2O3/NiO/CeO2/PVP nanocomposite its superior conductivity and efficient charge transfer. For Bi2O3/NiO/CeO2/PVP nanocomposite the charge transfer resistance (Rct) value is 104.18 Ω. Annual Methodological Archive Research Review 233 FIGURE 11: EIS PLOT OF BI2O3/NIO/CEO2/PVP NANOCOMPOSITE CONCLUSION In this research, theranostic agents and multifunctional nanoparticles composed of pure Bi2O3, Bi2O3/NiO, Bi2O3/NiO/CeO2, and Bi2O3/NiO/CeO2/PVP were synthesized using the Sol-gel method. Various characterization techniques, including X-ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), and Scanning Electron Microscopy (SEM), were employed to analyze these synthesized nanocomposites. The XRD patterns confirm that the fabricated samples exhibit a cubic crystalline structure. The average crystallite size was determined using the Scherrer formula for Bi2O3/NiO/CeO2/PVP, resulting in a crystallite size of 15.01 nm with a dislocation density of 0.00544 m-2. The FTIR spectra revealed absorption peaks corresponding to the Bi‒O, Ni-O bond, and Ce‒O bond, occurringintherangeof435505cm−1, 523 cm-1, and 489 cm−1, respectively, representing stretching vibrations. SEM analysis confirmed that the bismuth oxide particles were spherical, cerium oxide was agglomerated, and nickel oxide particles were relatively small in the nanocomposites of Bi2O3/NiO/CeO2/PVP. These optimized nanocomposites, Bi2O3/NiO/CeO2/PVP, demonstrated their potential as universal water-splitting electrocatalysts, performing both Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER) efficiently. Annual Methodological Archive Research Review 234 Extensive electrochemical tests, including CV, LSV, and EIS, revealed that these prepared nanocomposites exhibited higher current densities (10 mAcm-2) at significantly lower overpotential (190 mV and 25.7 mV vs RHE) and smaller Tafel slopes (88.3 mVdec-1and 261 mVdec-1) in the OER and HER compared to other composite materials. Furthermore, electrochemical impedance measurements indicated that the resistance of the modified electrode and the bare electrode ranged from 0 to 160 Ω.These results collectively emphasize the promising potential of Bi2O3/NiO-based nanocomposites as effective catalysts for sustainable water-splitting processes. Our work was focused on creating a highly stable and electrocatalytically active catalyst to enhance water splitting in an alkaline medium, using a straight forward and cost-effective method that can be readilyscaled for larger production volumes." REFERENCES Afaq, M., BaQais, A., et al. (2024). 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