NiCu bimetallic nanoparticle-decorated graphene as novel and cost-effective counter electrode for dye-sensitized solar cells and electrocatalyst for methanol oxidation

Motlak, M.,Barakat, N.A.M.,El-Deen, A.G.,Hamza, A.M.,Obaid, M.,Yang, O.B.,Akhtar, M.S.,Khalil, K.A. Elsevier 2015 Applied Catalysis A Vol.501 No.-

NiCu bimetallic nanoparticle-decorated graphene was prepared by hydrothermal treatment to be utilized as an efficient and alternative Pt-free counter electrode (CE) for dye-sensitized solar cells (DSSCs). The results indicated that the performance of the introduced modified graphene as CE strongly depends on the composition of the metallic nanoparticles. Typically, Ni-, Ni<SUB>0.25</SUB>Cu<SUB>0.75</SUB>-, Ni<SUB>0.6</SUB>Cu<SUB>0.4</SUB>- and Ni<SUB>0.75</SUB>Cu<SUB>0.25</SUB>-decorated graphene were synthesized. Investigation of the electrochemical characteristics indicated that the graphene decorated by Ni<SUB>0.75</SUB>Cu<SUB>0.25</SUB> nanoparticles shows the highest catalytic activity and conductivity compared to the other prepared formulations as well as pristine graphene. In DSSC, Ni<SUB>0.75</SUB>Cu<SUB>0.25</SUB> nanoparticle-decorated graphene can remarkably improve the catalytic activity toward triiodide reduction and lower the resistance at the electrolyte-CE interface. Accordingly, the obtained energy conversion efficiencies were 1.72%, 2.39%, 1.24%, 2.87% and 5.1% for pristine, Ni-, Ni<SUB>0.25</SUB>Cu<SUB>0.75</SUB>-, Ni<SUB>0.6</SUB>Cu<SUB>0.4</SUB>- and Ni<SUB>0.75</SUB>Cu<SUB>0.25</SUB>-decorated graphene, respectively. The obtained efficiency for Ni<SUB>0.75</SUB>Cu<SUB>0.25</SUB>-decorated graphene is comparable with Pt-based DSSC fabricated by the same procedure (5.9%) which recommends exploiting the introduced modified graphene as efficient and cost-effective CE for the large-scale fabrication of photovoltaic devices. The catalytic performance of the best formulation was examined toward methanol electrooxidation; the results indicated effective and stable electrocatalytic activity.

High-efficiency dye-sensitized solar cells based on nitrogen and graphene oxide co-incorporated TiO₂ nanofibers photoelectrode

Motlak, Moaaed,Barakat, Nasser A.M.,Akhtar, M. Shaheer,El-Deen, Ahmed G.,Obaid, M.,Kim, Cheol Sang,Khalil, Khalil Abdelrazek,Almajid, Abdulhakim A. Elsevier 2015 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.268 No.-

<P><B>Abstract</B></P> <P>For DSSCs application, highly efficient photoelectrode based on nitrogen (N) and graphene oxide (GO) co-incorporated TiO<SUB>2</SUB> nanofibers were synthesized successfully by two simple successive methods; electrospinning followed by hydrothermal processes. The influence of the N and GO co-incorporation on the morphology, crystal structure and optical behavior of TiO<SUB>2</SUB> nanofibers were characterized by various advanced techniques. The results showed that the modified TiO<SUB>2</SUB> nanofibers exhibit higher conversion energy in comparison to the mono-incorporated and pristine TiO<SUB>2</SUB> nanofibers. Optical and electrochemical properties study indicated that, compared to other GO contents, the 0.5wt% GO content provides higher surface area, more active sites for the dye absorption, and numerous hot electron transport paths to the FTO substrate which consequently improves the cell performance. On the other hand, N atoms incorporation causes positive shift of the flat band potentials (<I>V</I> <SUB>fb</SUB>) which leads to fast electron transport in TiO<SUB>2</SUB> nanofiber films and inhibits the charge recombination rate of photon-generated electrons. Accordingly, TiO<SUB>2</SUB> nanofibers co-incorporated by nitrogen and GO (0.5wt%) exhibit the best performance as photoanode in the DSSC, the corresponding conversion efficiency was 5.72% compared to 4.52% and 1.54% in case of nitrogen-free 0.5wt% GO-incorporated and pristine TiO<SUB>2</SUB> nanofibers, respectively. Overall, this study introduces nitrogen and graphene oxide co-incorporation in the titanium oxide nanofibers as novel strategy for enhancing the solar-to-electrical energy conversion in the DSSCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nitrogen and graphene oxide co-incorporated TiO<SUB>2</SUB> are introduced by simple methods. </LI> <LI> The introduced co-incorporated TiO<SUB>2</SUB> nanofibers reveal high efficiency; 5.72%. </LI> <LI> Co-incorporation leads to obtain high filling factor (FF=0.65). </LI> <LI> Co-incorporation has been used as novel strategy in the DSSCs. </LI> </UL> </P>

Carbon nanofibers doped by Ni_xCo_1-x alloy nanoparticles as effective and stable non precious electrocatalyst for methanol oxidation in alkaline media

Barakat, N.A.M.,Motlak, M.,Kim, B.S.,El-Deen, A.G.,Al-Deyab, S.S.,Hamza, A.M. Elsevier 2014 Journal of molecular catalysis Chemical Vol.394 No.-

Bimetallic alloys have superior physiochemical characteristics compared to the individual metals. In this study, Ni<SUB>x</SUB>Co<SUB>1-x</SUB> (x=0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) alloy nanoparticles incorporated in carbon nanofibers are investigated as electrocatalysts for methanol oxidation in the alkaline media. Preparation of the introduced nanofibers is achieved by calcination of electrospun nanofibers composed of nickel acetate, cobalt acetate and poly(vinyl alcohol) in argon atmosphere. The catalytic activity of cobalt enhances the carbonization of the utilized polymer which results in producing nickel/cobalt alloys nanoparticles embedded in carbon nanofibers. Due to the synergistic influence of the introduced alloy, both of the current density and onset potential were distinctly affected by the nanoparticles composition; Ni<SUB>0.5</SUB>Co<SUB>0.5</SUB> alloy nanoparticles-doped carbon nanofibers reveal current density and onset potential of 240mA/cm<SUP>2</SUP> and 110mV [vs. Ag/AgCl], respectively. Interestingly it was proofed that, compared to nanoparticles, the nanofibrous morphology has a distinct positive influence on the electrocatalytic activity due to the effect of the one dimensional structure which facilitates the electrons transfer and consequently decreases the IR drop. The introduced nanofibers showed good stability because of the alloy structure. Overall, this study opens new avenue for the transition metals alloys and the nanofibrous morphology to be invoked to produce novel and effective class of non-precious electrocatalysts.

Nickel nanoparticles-decorated graphene as highly effective and stable electrocatalyst for urea electrooxidation

Barakat, N.A.M.,Motlak, M.,Ghouri, Z.K.,Yasin, A.S.,El-Newehy, M.H.,Al-Deyab, S.S. Elsevier 2016 Journal of molecular catalysis Chemical Vol.421 No.-

<P>Among the various carbonaceous materials, graphene is highly considered to provide the optimum support for the electrocatalytic materials due to its excellent electrical conductivity and extremely large surface area. In literature, based on our best knowledge, few studies have been reported to introduce effective electrocatalysts for urea oxidation. In this study, Ni-decorated graphene sheets are introduced as effective and stable electrocatalyst for urea oxidation. The introduced composite was prepared by reflux of graphene oxide with nickel acetate at 120 degrees C for 10h followed by calcination in argon atmosphere at 850 degrees C for 2 h. X-ray diffractometer (XRD), transmission electron microscope (TEM) and Raman spectroscopy techniques confirmed formation of graphene sheets decorated by nickel nanoparticles. The synthesized Ni-decorate graphene shows distinct electrocatalytic activity toward urea oxidation. Numerically, using 2 M urea solution (in 1 M KOH) the corresponding current density was 150 mAcm(-2) (2100 mAcm(-2) g(-1)) with clear urea oxidation peaks in the forward and reverse scans. Study the influence of metal loading indicated that the amount of nickel nanoparticles should be optimized as the best performance has been observed when equal amounts of nickel acetate and graphene oxides were utilized during the preparation process. The introduced decorated graphene reveals good stability at various applied voltages. Overall, the study emphasizes the advantage of using graphene as support to distinctly enhancing urea electrooxidation. (C) 2016 Elsevier B.V. All rights reserved.</P>

Cobalt/Chromium Nanoparticles-Incorporated Carbon Nanofibers as Effective Nonprecious Catalyst for Methanol Electrooxidation in Alkaline Medium

Ibrahim M. A. Mohamed,Moaaed Motlak,H. Fouad,나지르 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.5

Cobalt-Chrome nanoparticles-incorporated carbon nanofibers (CNFs) are proposed as an effective nonprecious electrocatalyst for methanol oxidation in the alkaline media. The introduced nanofibers were prepared by simple technique, electrospinning. Carbonization of as-spun mat composed of chromium acetate, cobalt acetate and poly(vinyl alcohol) (PVA) at high temperature (900℃) leads to production of the introduced nanofibers. The physicochemical characteristics were investigated by X-ray diffractometer (XRD), scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM) equipped with EDX and TEM mapping. The exploited analyses confirmed that the final product is in the form of CNFs decorated by Co/Cr nanoparticles. Based on the results obtained from the cyclic voltammetry (CV) measurements, the proposed Co/Cr-incorporated CNFs possess high electrocatalytic activity toward methanol electrooxidation as a clear peak of methanol oxidation appeared with corresponding current density of 56 mA/cm2 . Moreover, the current density increased by increasing methanol concentration up to 4.0 M. Overall, the proposed nanofibers open new avenue for platinum-free and stable nanostructural catalysts for fuel cell technology.

Dissociative adsorption and self-assembly of CaF₂ on the Si(001)-4° off surface

김희동,Otgonbayar Dugerjav,Amarmunkh Arvishataar,Moaaed Motlak,서재명 한국진공학회 2012 한국진공학회 학술발표회초록집 Vol.2012 No.2

Surface reconstruction at the initial Ge adsorption stage on Si(114)-2 × 1

Duvjir, Ganbat,Kim, Hidong,Dugerjav, Otgonbayar,Li, Huiting,Motlak, Moaaed,Arvisbaatar, Amarmunkh,Seo, Jae M. American Vacuum Society 2013 Journal of vacuum science & technology. an officia Vol.31 No.2