Palladium Supported on Porous Chitosan-Graphene Oxide Aerogels as Highly Efficient Catalysts for Hydrogen Generation from Formate

[EN] Adsorption of Pd(NH3)(4)(2+) in preformed chitosan-graphene oxide (CS-GO) beads and their subsequent reduction with NaBH4 afford well-dispersed, high dispersion (similar to 21%) of uniformly sized Pd nanoparticles (similar to 1.7 nm). The resulting Pd/CS-GO exhibits interesting catalytic activity for hydrogen generation by ammonium formate decomposition. The optimal GO proportion of 7 wt% allows reaching, at 60 degrees C, a turnover frequency above 2200 h(-1)-being outstanding among the highest values reported for this process to date. Interestingly, no formation of CO or CH4 was detected. The catalyst did not leach, although it underwent gradual deactivation, probably caused by the increase in the Pd average size that became over 3 nm after three uses. Our results are relevant in the context of efficient on-board hydrogen generation from liquid organic hydrogen carriers in transportation.This research was funded by the Spanish Ministry of Science, Innovation and Universities (Grant RTI2018-098237-B-C21 and Severo Ochoa). A.P. also thanks the Spanish Ministry of Science and Education a research associate Ramon y Cajal contract. A.A. thanks UEMF for scholarship.Anouar, A.; Katir, N.; El Kadib, A.; Primo Arnau, AM.; García Gómez, H. (2019). Palladium Supported on Porous Chitosan-Graphene Oxide Aerogels as Highly Efficient Catalysts for Hydrogen Generation from Formate. Molecules. 24(18):1-13. https://doi.org/10.3390/molecules24183290S113241

Organophosphonate bridged anatase mesocrystals: low temperature crystallization, thermal growth and hydrogen photo-evolution

The sol-gel co-condensation of organo-phosphonates to titanium alkoxides enables access to novel organic-inorganic hybrids based on phosphonate-bridged titanium dioxide. In this contribution, we bring new perspectives to the long established sol-gel mineralization of titanium alkoxide species, by harnessing the virtues of the well-designed phosphonate-terminated phosphorus dendrimers as reactive amphiphilic nanoreactor, confined medium and cross-linked template to generate discrete crystalline anatase nanoparticles at low temperature (T = 60 degrees C). An accurate investigation on several parameters (dendrimer generation, dendrimer-to-titanium alkoxide ratio, precursor reactivity, temperature, solvent nature, salt effect) allows a correlation between the network condensation, the opening porous framework and the crystalline phase formation. The evolution of the dendrimer skeleton upon heat treatment has been deeply monitored by means of P-31 NMR, XPS and Raman spectroscopy. Increasing the heteroatom content within a titania network provides the driving force for enhancing their photocatalytic water splitting ability for hydrogen production.Brahmi, Y.; Katir, N.; Macia Agullo, JA.; Primo Arnau, AM.; Bousmina, M.; Majoral, J.; García Gómez, H.... (2015). Organophosphonate bridged anatase mesocrystals: low temperature crystallization, thermal growth and hydrogen photo-evolution. Dalton Transactions. 44(35):15544-15556. doi:10.1039/c5dt02367jS1554415556443

Pd embedded in chitosan microspheres as tunable soft-materials for Sonogashira cross-coupling in water-ethanol mixture

Easy shaping of chitosan (CS) as porous self-standing nanofibrillar microspheres allows their use as a palladium carrier. Amino-groups on CS enable the modulation of Pd coordination, giving rise to three different support-catalyst interactions: weakly-coordinated Pd-CS in native CS, incarcerated Pd-CS-Glu in cross-linked CS and strongly-ligated Pd-CS-SH, obtained by the introduction of thiol arms in CS. These catalysts efficiently promote Sonogashira cross-coupling of a large library of functional substrates under mild and sustainable conditions (water-ethanol as solvent at 65 degrees C) and stand as recyclable, metal-scavenging catalytic systems.Frindy, S.; Primo Arnau, AM.; Lahcini, M.; Bousmina, M.; García Gómez, H.; El Kadib, A. (2015). Pd embedded in chitosan microspheres as tunable soft-materials for Sonogashira cross-coupling in water-ethanol mixture. Green Chemistry. 17(3):1893-1898. doi:10.1039/c4gc02175dS18931898173Johansson Seechurn, C. C. C., Kitching, M. O., Colacot, T. J., & Snieckus, V. (2012). Palladium-Catalyzed Cross-Coupling: A Historical Contextual Perspective to the 2010 Nobel Prize. Angewandte Chemie International Edition, 51(21), 5062-5085. doi:10.1002/anie.201107017Sehnal, P., Taylor, R. J. K., & Fairlamb, I. J. S. (2010). Emergence of Palladium(IV) Chemistry in Synthesis and Catalysis. Chemical Reviews, 110(2), 824-889. doi:10.1021/cr9003242Torborg, C., & Beller, M. (2009). Recent Applications of Palladium-Catalyzed Coupling Reactions in the Pharmaceutical, Agrochemical, and Fine Chemical Industries. Advanced Synthesis & Catalysis, 351(18), 3027-3043. doi:10.1002/adsc.200900587Hartwig, J. F. (2008). Carbon–heteroatom bond formation catalysed by organometallic complexes. Nature, 455(7211), 314-322. doi:10.1038/nature07369Loska, R., Volla, C. M. R., & Vogel, P. (2008). Iron-Catalyzed Mizoroki-Heck Cross-Coupling Reaction with Styrenes. Advanced Synthesis & Catalysis, 350(18), 2859-2864. doi:10.1002/adsc.200800662Sun, C.-L., Li, B.-J., & Shi, Z.-J. (2011). Direct C−H Transformation via Iron Catalysis. Chemical Reviews, 111(3), 1293-1314. doi:10.1021/cr100198wCzaplik, W. M., Mayer, M., Cvengroš, J., & von Wangelin, A. J. (2009). Coming of Age: Sustainable Iron-Catalyzed Cross-Coupling Reactions. ChemSusChem, 2(5), 396-417. doi:10.1002/cssc.200900055Fürstner, A., Leitner, A., Méndez, M., & Krause, H. (2002). Iron-Catalyzed Cross-Coupling Reactions. Journal of the American Chemical Society, 124(46), 13856-13863. doi:10.1021/ja027190tBarluenga, J., & Valdés, C. (2011). Tosylhydrazones: New Uses for Classic Reagents in Palladium-Catalyzed Cross-Coupling and Metal-Free Reactions. Angewandte Chemie International Edition, 50(33), 7486-7500. doi:10.1002/anie.201007961Yin, & Liebscher, J. (2007). Carbon−Carbon Coupling Reactions Catalyzed by Heterogeneous Palladium Catalysts. Chemical Reviews, 107(1), 133-173. doi:10.1021/cr0505674Phan, N. T. S., Van Der Sluys, M., & Jones, C. W. (2006). On the Nature of the Active Species in Palladium Catalyzed Mizoroki–Heck and Suzuki–Miyaura Couplings – Homogeneous or Heterogeneous Catalysis, A Critical Review. Advanced Synthesis & Catalysis, 348(6), 609-679. doi:10.1002/adsc.200505473Weck, M., & Jones, C. W. (2007). Mizoroki−Heck Coupling Using Immobilized Molecular Precatalysts:  Leaching Active Species from Pd Pincers, Entrapped Pd Salts, and Pd NHC Complexes. Inorganic Chemistry, 46(6), 1865-1875. doi:10.1021/ic061898hWEBB, J., MACQUARRIE, S., MCELENEY, K., & CRUDDEN, C. (2007). Mesoporous silica-supported Pd catalysts: An investigation into structure, activity, leaching and heterogeneity. Journal of Catalysis, 252(1), 97-109. doi:10.1016/j.jcat.2007.09.007Garrett, C. E., & Prasad, K. (2004). The Art of Meeting Palladium Specifications in Active Pharmaceutical Ingredients Produced by Pd-Catalyzed Reactions. Advanced Synthesis & Catalysis, 346(8), 889-900. doi:10.1002/adsc.200404071Glasspoole, B. W., Webb, J. D., & Crudden, C. M. (2009). Catalysis with chemically modified mesoporous silicas: Stability of the mesostructure under Suzuki–Miyaura reaction conditions. Journal of Catalysis, 265(2), 148-154. doi:10.1016/j.jcat.2009.04.020Modak, A., Mondal, J., & Bhaumik, A. (2012). Pd-grafted periodic mesoporous organosilica: an efficient heterogeneous catalyst for Hiyama and Sonogashira couplings, and cyanation reactions. Green Chemistry, 14(10), 2840. doi:10.1039/c2gc35820dMacquarrie, D. J., & Hardy, J. J. E. (2005). Applications of Functionalized Chitosan in Catalysis†. Industrial & Engineering Chemistry Research, 44(23), 8499-8520. doi:10.1021/ie050007vA. El Kadib , ChemSusChem20158217244El Kadib, A., Primo, A., Molvinger, K., Bousmina, M., & Brunel, D. (2011). Nanosized Vanadium, Tungsten and Molybdenum Oxide Clusters Grown in Porous Chitosan Microspheres as Promising Hybrid Materials for Selective Alcohol Oxidation. Chemistry – A European Journal, 17(28), 7940-7946. doi:10.1002/chem.201003740El Kadib, A., & Bousmina, M. (2012). Chitosan Bio-Based Organic-Inorganic Hybrid Aerogel Microspheres. Chemistry - A European Journal, 18(27), 8264-8277. doi:10.1002/chem.201104006Kadib, A. E., Bousmina, M., & Brunel, D. (2014). Recent Progress in Chitosan Bio-Based Soft Nanomaterials. Journal of Nanoscience and Nanotechnology, 14(1), 308-331. doi:10.1166/jnn.2014.9012Primo, A., & Quignard, F. (2010). Chitosan as efficient porous support for dispersion of highly active gold nanoparticles: design of hybrid catalyst for carbon–carbon bond formation. Chemical Communications, 46(30), 5593. doi:10.1039/c0cc01137aValentin, R., Molvinger, K., Quignard, F., & Brunel, D. (2003). Supercritical CO2 dried chitosan: an efficient intrinsic heterogeneous catalyst in fine chemistry. New Journal of Chemistry, 27(12), 1690. doi:10.1039/b310109fPrimo, A., Atienzar, P., Sanchez, E., Delgado, J. M., & García, H. (2012). From biomass wastes to large-area, high-quality, N-doped graphene: catalyst-free carbonization of chitosan coatings on arbitrary substrates. Chemical Communications, 48(74), 9254. doi:10.1039/c2cc34978gNgah, W. S. W., Ab Ghani, S., & Kamari, A. (2005). Adsorption behaviour of Fe(II) and Fe(III) ions in aqueous solution on chitosan and cross-linked chitosan beads. Bioresource Technology, 96(4), 443-450. doi:10.1016/j.biortech.2004.05.022El Hankari, S., El Kadib, A., Finiels, A., Bouhaouss, A., Moreau, J. J. E., Crudden, C. M., … Hesemann, P. (2011). SBA-15-Type Organosilica with 4-Mercapto-N,N-bis-(3-Si-propyl)butanamide for Palladium Scavenging and Cross-Coupling Catalysis. Chemistry - A European Journal, 17(32), 8984-8994. doi:10.1002/chem.201002190Crudden, C. M., Sateesh, M., & Lewis, R. (2005). Mercaptopropyl-Modified Mesoporous Silica:  A Remarkable Support for the Preparation of a Reusable, Heterogeneous Palladium Catalyst for Coupling Reactions. Journal of the American Chemical Society, 127(28), 10045-10050. doi:10.1021/ja0430954McEleney, K., Crudden, C. M., & Horton, J. H. (2009). X-ray Photoelectron Spectroscopy and the Auger Parameter As Tools for Characterization of Silica-Supported Pd Catalysts for the Suzuki−Miyaura Reaction. The Journal of Physical Chemistry C, 113(5), 1901-1907. doi:10.1021/jp808837kRoy, A. S., Mondal, J., Banerjee, B., Mondal, P., Bhaumik, A., & Islam, S. M. (2014). Pd-grafted porous metal–organic framework material as an efficient and reusable heterogeneous catalyst for C–C coupling reactions in water. Applied Catalysis A: General, 469, 320-327. doi:10.1016/j.apcata.2013.10.017Kadib, A. E., Molvinger, K., Cacciaguerra, T., Bousmina, M., & Brunel, D. (2011). Chitosan templated synthesis of porous metal oxide microspheres with filamentary nanostructures. Microporous and Mesoporous Materials, 142(1), 301-307. doi:10.1016/j.micromeso.2010.12.012Kühbeck, D., Saidulu, G., Reddy, K. R., & Díaz, D. D. (2012). Critical assessment of the efficiency of chitosan biohydrogel beads as recyclable and heterogeneous organocatalyst for C–C bond formation. Green Chem., 14(2), 378-392. doi:10.1039/c1gc15925aKhalafi-Nezhad, A., & Mohammadi, S. (2014). Chitosan supported ionic liquid: a recyclable wet and dry catalyst for the direct conversion of aldehydes into nitriles and amides under mild conditions. RSC Advances, 4(27), 13782. doi:10.1039/c3ra43440kEl Kadib, A., McEleney, K., Seki, T., Wood, T. K., & Crudden, C. M. (2011). Cross-Coupling in the Preparation of Pharmaceutically Relevant Substrates using Palladium Supported on Functionalized Mesoporous Silicas. ChemCatChem, 3(8), 1281-1285. doi:10.1002/cctc.20110002

Insightful understanding of the role of clay topology on the stability of biomimetic hybrid chitosan-clay thin films and CO2-dried porous aerogel microspheres

[EN] Three natural clay-based microstructures, namely layered montmorillonite (MMT), nanotubular halloysite (HNT) and micro-fibrillar sepiolite (SP) were used for the synthesis of hybrid chitosan-clay thin films and porous aerogel microspheres. At a first glance, a decrease in the viscosity of the three gel forming solutions was noticed as a result of breaking the mutual polymeric chains interaction by the clay microstructure. Upon casting, chitosan-clay films displayed enhanced hydrophilicity in the order CS < CS-MMT < CS-HNT < CS-SP. Irrespective to the clay microstructure, an improvement in the mechanical properties of the chitosan-clay films has been substantiated with CS-SP reaching the highest value at 5% clay loading. While clay addition provides a way to resist the shrinkage occurring for native chitosan, the enhanced hydrophilicity associated to the water content affects the efficacy of the CO2 super-critical drying as the most hydrophilic CS-SP microspheres face the highest shrinkage, resulting in a lowest specific surface area compared to CS-HNT and CS-MMT. Chitosan-clay exhibits enhanced thermal properties with the degradation delayed in the order CS < CS-MMT < CS-HNT < CS-SP. Under acidic environment, a longevity has been substantiated for chitosan-clay compared to native chitosan, evidencing the beneficial protective effect of the clay particulates for the biopolymer. However, under hydrothermal treatment, the presence of clay was found to be detrimental to the material stability as a significant shrinkage occurs in hybrid CS-clay microspheres, which is attributed again to their increased hydrophilicity compared to the native polymeric microspheres. In this framework, a peculiar behavior was observed for CS-MMT, with the microspheres standing both against contraction during CO2 gel drying and under hydrothermal conditions. The knowledge gained from this rational design will constitute a guideline toward the preparation of ultra-stable, practically-optimized food-packaging films and commercially scalable porous bio-based adsorbents.S. F thanks MAScIR foundation, CNRST and Erasmus Mundus-Maghreb & Egypt- EMMAG.Frindy, S.; Primo Arnau, AM.; Qaiss, AEK.; Bouhfid, R.; Lahcini, M.; García Gómez, H.; Bousmina, M.... (2016). Insightful understanding of the role of clay topology on the stability of biomimetic hybrid chitosan-clay thin films and CO2-dried porous aerogel microspheres. Carbohydrate Polymers. 146:353-361. doi:10.1016/j.cabpel.2016.03.022S35336114

Remarkable Activity of 002 Facet of Ruthenium Nanoparticles Grown on Graphene Films on the Photocatalytic CO2 Methanation

[EN] In the context of diminishing atmospheric CO2 emissions, there is an urgent need to develop processes that can be carried out at a scale commensurate with appropriate CO2 volumes. One possible reaction is the transformation of CO2 to methane (Sabatier reaction). Due to its chemical stability, catalytic CO2 hydrogenation to methane is carried out at temperatures of 450 degrees C or higher and pressures above 5 bars, thus, requiring a significant energy input. One alternative possibility to conventional thermal catalysis is the use of solar light as the primary energy, performing the photocatalytic CO2 hydrogenation. In this broad context, the present study shows the photocatalytic activity of nanometric films of oriented Ru nanoparticles (NPs) strongly grafted on defective graphene. These graphene films (thinner than 20 nm) containing Ru NPs nanoplatelets (less than 2 nanomol(Ru)/cm(2)) are among the most active photocatalysts ever prepared for CO2 hydrogenation and operate through photoinduced charge separationSupport by the Ministerio de Ciencia e Innovacion (Severo Ochoa and RTI2018-098237-B-C21) and Generalitat Valenciana (Prometeo 2017/083) was acknowledged. Thanks are due to Galicia Supercomputing Center. A.A. thanks UEMF (Euromed Unniversity Fes) and UPV for an Erasmus+ 2019-1-ES01-KA107-062073 Scholarship. A.P. thanks the Spanish Ministry for a Ramon y Cajal research associate contract.Anouar, A.; García-Aboal, R.; Atienzar Corvillo, PE.; Franconetti, A.; Katir, N.; El Kadib, A.; Primo Arnau, AM.... (2022). Remarkable Activity of 002 Facet of Ruthenium Nanoparticles Grown on Graphene Films on the Photocatalytic CO2 Methanation. Advanced Sustainable Systems. 6(5):1-10. https://doi.org/10.1002/adsu.2021004871106

111 oriented gold nanoplatelets on multilayer graphene as visible light photocatalyst for overall water splitting

[EN] Development of renewable fuels from solar light appears as one of the main current challenges in energy science. A plethora of photocatalysts have been investigated to obtain hydrogen and oxygen from water and solar light in the last decades. However, the photon-to-hydrogen molecule conversion is still far from allowing real implementation of solar fuels. Here we show that 111 facet-oriented gold nanoplatelets on multilayer graphene films deposited on quartz is a highly active photocatalyst for simulated sunlight overall water splitting into hydrogen and oxygen in the absence of sacrificial electron donors, achieving hydrogen production rate of 1.2 molH2 per gcomposite per h. This photocatalytic activity arises from the gold preferential orientation and the strong gold–graphene interaction occurring in the composite system.Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa and CTQ2012-32315) and Generalitat Valenciana (Prometeo 2013-019) is gratefully acknowledged. D.M. and I.E.-A. thank to Spanish Ministry of Science for PhD scholarships.Mateo Mateo, D.; Esteve Adell, I.; Albero Sancho, J.; Sánchez Royo, JF.; Primo Arnau, AM.; García Gómez, H. (2016). 111 oriented gold nanoplatelets on multilayer graphene as visible light photocatalyst for overall water splitting. Nature Communications. 2016(7):1-8. https://doi.org/10.1038/ncomms11819S1820167Lv, X. J., Zhou, S., Huang, X., Wang, C. & Fu, W. F. Photocatalytic overall water splitting promoted by SnOx-NiGa2O4 photocatalysts. Appl. Cat. B: Environ. 182, 220–228 (2016).Xu, J., Wang, L. & Cao, X. Polymer supported graphene-CdS composite catalyst with enhanced photocatalytic hydrogen production from water splitting under visible light. Chem. Eng. J. 283, 816–825 (2016).Tanigawa, S. & Irie, H. Visible-light-sensitive two-step overall water-splitting based on band structure control of titanium dioxide. Appl. Cat. B: Environ. 180, 1–5 (2016).Maeda, K. et al. GaN:ZnO solid solution as a photocatalyst for visible-light-driven overall water splitting. J. Am. Chem. Soc. 127, 8286–8287 (2005).Maeda, K. et al. Photocatalyst releasing hydrogen from water. Nature 440, 295 (2006).Kato, H. & Kudo, A. Visible-light-response and photocatalytic activities of TiO2 and SrTiO3 photocatalysts codoped with antimony and chromium. J. Phys. Chem. B 106, 5029–5034 (2002).Xiang, Q., Cheng, B. & Yu, J. Graphene-based photocatalysts for solar-fuel generation. Angew. Chem. Int. Ed. 54, 11350–11366 (2015).Navalon, S., Dhakshinamoorthy, A., Alvaro, M. & Garcia, H. Carbocatalysis by graphene-based materials. Chem. Rev. 114, 6179–6212 (2014).Yu, J., Jin, J., Cheng, B. & Jaroniec, M. A noble metal-free reduced graphene oxide-cds nanorod composite for the enhanced visible-light photocatalytic reduction of CO2 to solar fuel. J. Mat. Chem. A 2, 3407–3416 (2014).Meng, F., Cushing, S. K., Li, J., Hao, S. & Wu, N. Enhancement of solar hydrogen generation by synergistic interaction of La2Ti2O7 photocatalyst with plasmonic gold nanoparticles and reduced graphene oxide nanosheets. ACS Catal. 5, 1949–1955 (2015).Shown, I. et al. Highly efficient visible light photocatalytic reduction of co2 to hydrocarbon fuels by cu-nanoparticle decorated graphene oxide. Nano Lett. 14, 6097–6103 (2014).Shang, L. et al. Graphene-supported ultrafine metal nanoparticles encapsulated by mesoporous silica: robust catalysts for oxidation and reduction reactions. Angew. Chem. Int. Ed. 53, 250–254 (2014).Latorre-Sánchez, M., Primo, A. & García, H. P-doped graphene obtained by pyrolysis of modified alginate as a photocatalyst for hydrogen generation from water-methanol mixtures. Angew. Chem. Int. Ed. 52, 11813–11816 (2013).Lavorato, C., Primo, A., Molinari, R. & Garcia, H. N-doped graphene derived from biomass as a visible-light photocatalyst for hydrogen generation from water/methanol mixtures. Chem. - A Eur. J. 20, 187–194 (2014).Shams, S. S., Zhang, L. S., Hu, R., Zhang, R. & Zhu, J. Synthesis of graphene from biomass: a green chemistry approach. Mater. Lett. 161, 476–479 (2015).Meng, F. et al. Biomass-derived high-performance tungsten-based electrocatalysts on graphene for hydrogen evolution. J. Mater. Chem. A 3, 18572–18577 (2015).Vilatela, J. J. & Eder, D. Nanocarbon composites and hybrids in sustainability: a review. ChemSusChem 5, 456–478 (2012).Rani, P. & Jindal, V. K. Designing band gap of graphene by B and N dopant atoms. RSC Adv. 3, 802–812 (2013).Zheng, Y. et al. Hydrogen evolution by a metal-free electrocatalyst. Nat. Commun. 5, 3783 (2014).Wang, X. et al. A metal-free polymeric photocatalyst for hydrogen production from water under visible light. Nat. Mater. 8, 76–80 (2009).Huang, H., Yang, S., Vajtai, R., Wang, X. & Ajayan, P. M. Pt-decorated 3D architectures built from graphene and graphitic carbon nitride nanosheets as efficient methanol oxidation catalysts. Adv. Mater. 26, 5160–5165 (2014).Shiraishi, Y. et al. Platinum nanoparticles strongly associated with graphitic carbon nitride as efficient co-catalysts for photocatalytic hydrogen evolution under visible light. Chem. Commun. 50, 15255–15258 (2014).G. Baldoví, H. et al. Visible-light photoresponse of gold nanoparticles supported on TiO2: A combined photocatalytic, photoelectrochemical, and transient spectroscopy study. ChemPhysChem 16, 335–341 (2015).Serra, M., Albero, J. & Garcia, H. Photocatalytic Activity of Au/TiO2 photocatalysts for H-2 evolution: role of the Au nanoparticles as a function of the irradiation wavelength. ChemPhysChem 16, 1842–1845 (2015).Gomes Silva, C., Juárez, R., Marino, T., Molinari, R. & García, H. Influence of excitation wavelength (UV or visible light) on the photocatalytic activity of titania containing gold nanoparticles for the generation of hydrogen or oxygen from water. J. Am. Chem. Soc. 133, 595–602 (2011).El Kadib, A. Chitosan as a sustainable organocatalyst: a concise overview. ChemSusChem 8, 217–244 (2015).Primo, A., Atienzar, P., Sanchez, E., Delgado, J. M. & García, H. From biomass wastes to large-area, high-quality, N-doped graphene: catalyst-free carbonization of chitosan coatings on arbitrary substrates. Chem. Commun. 48, 9254–9256 (2012).Primo, A. & Quignard, F. Chitosan as efficient porous support for dispersion of highly active gold nanoparticles: design of hybrid catalyst for carbon-carbon bond formation. Chem. Commun. 46, 5593–5595 (2010).Primo, A. et al. One-step pyrolysis preparation of 1.1.1 oriented gold nanoplatelets supported on graphene and six orders of magnitude enhancement of the resulting catalytic activity. Angew. Chem. Int. Ed. 54, 1–7 (2015).Lalov, I. G., Guerginov, I. I., Krysteva, M. A. & Fartsov, K. Treatment of waste water from distilleries with chitosan. Water Res. 34, 1503–1506 (2000).No, H. K. & Meyers, S. P. Application of Chitosan for Treatment of Wastewaters in Reviews of Environmental Contamination and Toxicology: Continuation of Residue Reviews eds George W. W. 1–27Springer (2000).Liu, C. et al. Hydrothermal synthesis of N-doped TiO2 nanowires and N-doped graphene heterostructures with enhanced photocatalytic properties. J. Alloys Compd. 656, 24–32 (2016).Radnik, J., Mohr, C. & Claus, P. On the origin of binding energy shifts of core levels of supported gold nanoparticles and dependence of pretreatment and materials synthesis. Phys. Chem. Chem. Phys. 5, 172–177 (2003).Primo, A. et al. High catalytic activity of oriented 2.0.0 copper(I) oxide grown on graphene film. Nat. Commun. 6, 8561 (2015).Abbasi, M. et al. Application of transmitted Kikuchi diffraction in studying nano-oxide and ultrafine metallic grains. ACS Nano 9, 10991–11002 (2015).Trimby, P. T. Orientation mapping of nanostructured materials using transmission kikuchi diffraction in the scanning electron microscope. Ultramicroscopy 120, 16–24 (2012).Johnson, C. J., Dujardin, E., Davis, S. A., Murphy, C. J. & Mann, S. Growth and form of gold nanorods prepared by seed-mediated, surfactant-directed synthesis. J. Mater. Chem. 12, 1765–1770 (2002).Ikeda, S. et al. Mechano-catalysis—a novel method for overall water splitting. Phys. Chem. Chem. Phys. 1, 4485–4491 (1999).Khalid, N. R., Ahmed, E., Hong, Z., Sana, L. & Ahmed, M. Enhanced photocatalytic activity of graphene-TiO2 composite under visible light irradiation. Curr. Appl. Phys. 13, 659–663 (2013).Singh, G. P., Shrestha, K. M., Nepal, A., Klabunde, K. J. & Sorensen, C. M. Graphene supported plasmonic photocatalyst for hydrogen evolution in photocatalytic water splitting. Nanotechnology 25, 265701 (2014).Wang, M., Han, J., Xiong, H. & Guo, R. Yolk@shell nanoarchitecture of Au@r-GO/TiO2 hybrids as powerful visible light photocatalysts. Langmuir 31, 6220–6228 (2015).Luo, Z. et al. Modulating the electronic structures of graphene by controllable hydrogenation. Appl. Phys. Lett. 97, 233111 (2010).Sridhara Rao, D. V., Muraleedharan, K. & Humphreys, C. J. in Microscope Science, Technology, Applications and Education 3, 1232–1244Formatec (2010)