Browsing by Author "Nazir, Roshan"
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Item Open Access Development of CuAg/Cu2O nanoparticles on carbon nitride surface for methanol oxidation and selective conversion of carbon dioxide into formate(Elsevier, 2020) Nazir, Roshan; Kumar, A.; Saad, M. A. S.; Ali, S.Herein we report a catalyst consisting of CuAg/Cu2O nanoparticles (NPs), synthesized on the two-dimensional carbon nitride (Csingle bondN) surface via galvanic exchange route for electrocatalytic methanol oxidation and carbon dioxide reduction. The lower reduction potential of copper ([Cu+(aq) + e− → Cu(s)], + 0.52 eV) compared to Ag ([Ag+(aq) + e− → Ag(s)], +0.80 eV) makes Cu(0) easily exchangeable by Ag+ ions via galvanic exchange without applying any external bias. In a two-step process, the Cu NPs are synthesized first on Csingle bondN surface by adsorbing Cu2+ precursors and reducing them by NaBH4. Due to unstable nature of Cu2+ in aqueous medium some Cu2O NPs (a mixed phase of Cu/CuO) were also formed. Thereafter in the second step, Ag+ precursors are brought in contact with the already synthesized Cu and Cu2O nanoparticles (NPs). The Cu and Cu2O NPs present on the surface of Csingle bondN are partially exchanged by Ag atoms to generate bimetallic CuAg/Cu2O NPs. Two atoms of Ag are expected to be deposited for every Cu atom replaced. As galvanic replacement occurs on the solid surface of carbon nitride, there is only a partial replacement of Cu and Cu2O atoms. The catalysts Csingle bondN/Cu/Cu2O and Csingle bondN/CuAg/Cu2O were evaluated for their performance towards methanol oxidation and carbon dioxide reduction. Csingle bondN/CuAg/Cu2O showed twice the current density for methanol oxidation than Csingle bondN/Cu/Cu2O in a 0.5 M methanol solution. Probably the reason for high activity of Ag than Cu is related to the weak bond of oxygen on silver substrate for oxidation reactions and strong binding affinity on copper substrate. In case of carbon dioxide reduction (CO2 reduction) the product was identified to be formate by oxidizing the product (formate) on a Pt ring electrode. The results revealed Csingle bondN/CuAg/Cu2O shows a better selectivity towards formic acid formation than Csingle bondN/Cu/Cu2O using the rotating ring disc electrode (RRDE). A probable reason may be the strain induced by alloy formation which could favor a reduced coverage of adsorbed hydrogen and a decrease in oxophilicity of the compressively strained copper.Item Open Access Nanocomposite synthesis of silver doped magnesium oxide incorporated in PVC matrix for photocatalytic applications(Springer, 2021-04-08) Rouabah, N.; Boudine, B.; Nazir, Roshan; Zaabat, M.; Alqahtani, A. S.; Alqahtani, M. S.; Syed, R.This work reveals a sol–gel approach for synthesis of silver doped magnesium oxide (Ag:MgO) incorporated in PVC matrix to give Ag:MgO/PVC nanocomposite. On glass substrate three different percentages of Ag:MgO/PVC (3,7, and 10%) were deposited by spin coating method. This film of Ag:MgO/PVC nanocomposites were characterized using AFM, UV–Vis, XRD and FTIR analysis. The results of XRD revealed the formation of Ag doped MgO nanoparticles with two phases (MgO and metallic Ag) in the matrix of PVC with the average size of nanoparticles equal to 31.5,22.29, 23.77, 29.68 nm. The direct band gap energy for PVC and pure MgO/PVC was 4.1 eV and 3.85 eV respectively. The band gap energy value changes from 3.85 eV, 3.75 eV, 3.71 eV, 3.69 eV with increasing Ag:MgO concentration(3–10%). Atomic force microscopyalso shows a change in the roughness of the nanocomposites film with increasing Ag:MgO nanoparticles percentage. The photocatalytic activity of this nanocomposite film was evaluated for the methylene blue (MB) dye under UV light irradiation. The result demonstrated good potential of Ag:MgO/PVC nanocomposites films for MB degradation with a suitable photocatalytic reaction proposed mechanism. The kinetic studies revealed a rate constant of 6.25 × 10–3 min−1 for 10% Ag:MgO/PVC nanocomposite thin films.Item Open Access Nanosheet synthesis of mixed Co3O4/CuO via combustion method for methanol oxidation and carbon dioxide reduction(American Chemical Society, 2020) Nazir, Roshan; Khalfani, A.; Abdelfattah, O.; Kumar, A.; Saad, M. A. S.; Ali, S.This paper represents a study of mixed Co3O4/CuO nanosheet (NS) synthesis via solution combustion synthesis for oxidation of methanol and carbon dioxide (CO2) conversion. The mixed oxide NS of Co3O4/CuO is a hybrid structure of Co3O4 and CuO NSs. We applied this mixed oxide NS of Co3O4/CuO for methanol oxidation and carbon dioxide (CO2) conversion, and the results revealed that the activity of the mixed oxide NS surpassed the activity of the corresponding individual Co3O4 and CuO metal oxide NSs, both in methanol oxidation and in CO2 conversion. The mass activity of the mixed Co3O4/CuO NS produced at 0.627 V versus Ag/AgCl during methanol oxidation (0.5 M) was 12 mA g–1, which is 2.4 times better than that of Co3O4, whose mass activity is 5 mA g–1, and 4 times better than that of the CuO NS, whose mass activity is 3 mA g–1. The methanol oxidation peak at 0.62 V versus Ag/AgCl was also more intense than individual oxides. The trend in performance of methanol oxidation follows the order: Co3O4/CuO > Co3O4 > CuO. In the case of CO2 reduction, we experienced that our product was formate, and this was proved by formate oxidation (formate is formed as a product during the reduction of CO2) on the surface of the Pt ring of a rotating ring-disc electrode. Similar to methanol oxidation, Co3O4/CuO also showed superior activity in carbon dioxide reduction. It was experienced that at −1.5 V, the current density rises to −24 mA/cm2 for the Co3O4/CuO NS, that is, 0.6 times that of the CuO NS, which is −15 mA/cm2, and 3 times more than that of the Co3O4 NS, which is 8 mA/cm2. The trend in performance of CO2 reduction follows the order: Co3O4/CuO > CuO > Co3O4.Item Open Access Preparation and properties of electrodeposited Ni-B-V2O5 composite coatings(Elsevier, 2021-01-17) Waware, U. S.; Nazir, Roshan; Prasad, A.; Hamouda, A. M. S.; Pradhan, A. K.; Alshehri, M.; Syed, R.; Malik, A.; Alqahtan, M. S.Coatings of Ni-B have gained significant importance in various industries owing to their major role in improving mechanical properties including hardness, conductivity, and wear resistance. Despite all these characteristic features, there is still the need for a lot of modifications. This is to improve the properties of the coating so as to increase their durability and overall performance. The current study is based on development of Ni-B-V2O5 composite coating on mild steel substrate through the electrodeposition technique and the investigation of mechanical and anti-corrosive properties of the formed coating. The incorporation of V2O5 particles into the composite coating was confirmed by energy dispersive spectroscopy. X-ray diffraction pattern showed amorphous nature of electrodeposited Ni-B matrix, while the crystalline nature improved with the addition of V2O5 particles to the composite. Field emission scanning electron microscopy and atomic force microscopic studies clearly indicated that the addition of V2O5 particles to the Ni-B coating increased the surface roughness. Further studies reveal increase in the micro-hardness (by 171.11%), and elastic modulus (by 9.4%) in case of the Ni-B-V2O5 composite coating relative to the Ni-B coating. The enhanced micro-hardness was attributed to the inclusion of hard V2O5 particles into the Ni-B matrix, which in turn, may inhibit the dislocation motion in the composite. An increase in corrosion resistance (by 229%) was also experienced in the electrodeposited Ni-B-V2O5 composite coating in comparison to the bare Ni-B matrix, which may be due to the masking of inert V2O5 particles on the active region of the Ni-B composite.Item Open Access Synthesis of hydroxide nanoparticles of Co/Cu on carbon nitride surface via galvanic exchange method for electrocatalytic CO2 reduction into formate(Elsevier, 2020-04-06) Nazir, Roshan; Kumar, A.; Saad, M. A. S.; Ashok, A.; Nazir, RoshanHerein we report Co and Cu based metal hydroxides (Co(OH)2/Cu(OH)2) on carbon nitride (C3N4) surface via replacement of Co nanoparticles (NPs) through galvanic exchange method for electrocatalytic carbon dioxide reduction. The lower value of reduction potential in case of cobalt ([Co+(aq) + 2e− → Co(s)], −0.28 eV) compared to copper ([Cu2+(aq) +2 e− → Cu(s)], +0.34 eV) makes Co(0) easily susceptible to galvanic exchange process. On the basis of this significant difference in the reduction potential of Cu(0) and Co(0), 0.62 V, Cu2+ can replace Co(0) via galvanic exchange without using any external bias. The synthesis of (Co(OH)2/Cu(OH)2) involves two steps, where in the first step on surface of C3N4, Co NPs were synthesized via reducing of Co2+ ions with a strong reducing agent NaBH4. In presence of aqueous medium, formation of cobalt hydroxide also takes place. In the second step these cobalt nanoparticles on C3N4 were subjected to the process of galvanic exchange in which the sacrificial Co NPs were exchanged by Cu atoms and forming Cu(OH)2 in presence of an aqueous medium. Overall, the whole synthesis process results in deposition of hydroxides of cobalt and copper (C3N4/(Co(OH)2/Cu(OH)2) on C3N4 surface. The synthesized materials were characterized using PXRD, EDS, XPS, TEM and SEM. The two electrocatalysts C3N4/(Co/Co(OH)2 C3N4/(Co(OH)2/Cu(OH)2 were evaluated for their performance towards carbon dioxide reduction. C3N4/(Co(OH)2/Cu(OH)2 showed superior performance with electrocatalytic activity more than three times of C3N4/(Co/Co(OH)2. The product of CO2 electro-reduction was identified, using a rotating ring disc electrode (RRDE) system, to be primarily formate.