The hydrogen cycle with the hydrolysis of sodium borohydride: a statistical approach for highlighting the scientific/technical issues to prioritize in the field

Umit B. DEMIRCIIEM (Institut Europeen des Membranes), UMR 5635 (CNRS-ENSCM-UM2), Universite Montpellier 2, Place E. Bataillon, F-34095, Montpellier, France, Tel. +33(0)4.67.14.91.60, Fax +33(0)4.67.14.91.19, Email: umit.demirci@um2.fr

Supplementary dataHereafter are shown Figures S1 to S8, and Table S1.

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Figure S1. Histogram representing the proportions of research articles among the 260 ones as a function of the number of pages (varying from 3 to 15 pages).

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Figure S2. List of the main journals, i.e. those having published 79% of the research articles analyzed in the present work.

Figure S3. List of the other (minor) journals, i.e. those having published 21% of the research articles analyzed in the present work.

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Figure S4. Histogram representing the proportions of research articles among the 260 ones as a function of the number of (co-)authors (varying from 1 author to 10 co-authors). Information about the number of corresponding author(s) by paper is given in insert.

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Figure S5. Proportion of the research articles according to the number of institutions (from 1 to 5) involved in the reported works, and statistical information about the national (Nat. Collab.) and international (Int. Collab.) collaborations.

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Figure S6. Number and locations of the private institutions having a contribution in ca. 11% of the 260 research articles.

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Figure S7. Proportion of the research articles as a function of the number of keywords they report.

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Figure S8. Percentage of the research articles as a function of the molar ratio H2O/NaBH4. The x axis is in log scale. The molar ratios are shown by ranges: [2-6], ]6-20], ]20-42], ]42-100], ]100-500], ]500-1200].

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Table S1. List of all of the keywords cited in the 260 research articles.AAcetate Acetic acid Acetylacetonate Acid acceleratorAcid catalysis Acids Activate(d) carbon Activation energyAir-independent propulsion (AIP)

Al Alcoholysis Alkaline NaBH4 gel

Alkaline sodium borohydride

Al-Li alloy Al-Li-Co/NaBH4 system Alloy(s) (catalyst)

Alumina Aluminum (powder) Aluminum alloys Aluminum chlorideAmmonia borane Analytical model Anion effect Aqueous acidAttapulgite clayBBall-milling Batch reactor Borate conversion rate Borates coatingBorax (anhydrous) Borohydride Borohydride hydrolysis BoronBy-productCCalcination temperature Calcium deficient Calorimetry Capacitive deionizationCapacity Capsule Carbon aerogels Carbon clothCarbon nanotube support Carbon support Catalysis Catalyst poisoningCatalyst(s) Catalytic action Catalytic efficiency Catalytic hydrolysisCatalytic reaction Catalytic solution Cathodic reduction Caustic corrosionChemical hydride(s) Chemical hydrogen

storageChemical synthesis Co-Ni-B films

Clay Co film Co supported catalysts Co(-)B catalystCo2B Co3O4 CoB Co-BCobalt Cobalt (III) oxide Cobalt borate Cobalt borideCobalt boride reduction Cobalt catalyst

deactivationCobalt catalyst reactivation

Cobalt dichloride

Cobalt loading Cobalt nanoparticles Cobalt salt Cobalt supported over nickel

Cobalt-boron alloy Cobalt-manganese-boride catalyst

Cobalt-molybdenum-boron catalyst

Cobalt-phosphorus catalyst

Cobalt-wolfram-boron catalyst

CoCl2 Co-Cr-B catalyst Co-Fe-B catalyst

Co-La-Zr-B Colloidal carbon spheres Combinatorial CombustionCoMoMnB electrodeposition

Co-Mo-Pd-B Composite (materials) Co-Ni-B catalyst

Co-Ni-P catalyst Continuous reactor Controlled synthesis Co-P catalystCo-P/Ni foam catalysts Co-P-B catalyst Copper-cobalt complex Core-shell catalystCo-Ru-N catalyst Co-supported on alumina Co-W-B amorphous

catalystCrystal structure

Crystalline water Crystallization Cyclic voltammetryDDeactivation Degradation Dehydrogenation Dicationic ionic liquidDirect borohydride fuel cell (DBFC)

Durability (of catalyst) Dynamic polymers Dynamic template

EElectrical field Electrochemical

regulationElectrodeposition Electroless deposition

Electroless plating Electronic load Electrophoretic deposition

Electroplating

Electrospinning Electrostatic repulsion Electrosynthesis Energy systemsEvolved heatFFalling film hydrogen generation

Fe-B catalyst Ferric catalysts Ferromagnetic metals

Filamentary nickel Flight test Flow measurements FluorinationFourier transformed IR spectroscopy

FTIR Fuel cell unmanned aircraft

Fuel cell(s)

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Functionalized carbon nanotubeGGas chromatography Gas-volumetric technique Gel GMA-IDAGraphene nanosheets Graphite Gravimetric hydrogen

storage capacityHH2 generation Heat of reaction Heterogeneous catalysis HeteropolyanionsHigh conversion High energy density

deviceHigh pressure Holes

Homogeneous catalysis Hybrid power system Hydrated metaborate Hydrated sodium boratesHydride generation Hydrogel Hydrogen (gas) Hydrogen carrierHydrogen efficiency Hydrogen energy Hydrogen evolution Hydrogen generationHydrogen generation rate Hydrogen on demand Hydrogen peroxide Hydrogen productionHydrogen purity Hydrogen release Hydrogen storage Hydrogen storage and

productionHydrogen storage material(s)

Hydrogen(-)generator(s) Hydrogenophosphate Hydrolysis

Hydrolysis (of) sodium borohydride

Hydrolysis mechanism Hydrolysis reaction Hydrophobic membrane

Hydroxyapatite (support) Hydroxyborate anionsIIn In situ monitoring Induction period Integrated reactorIon-exchange Ionic liquids Iron boride nanoparticles Iron nanoclustersKKinetic(s) (study)LLangmuir-Hinshelwood model

Laser ablation LiCoO2 (preparation) Liquid catalysis

Liquid-solid reactions Lithium cobalt oxideMMagnesium Magnesium hydride Magnetic reactor Magnetic recycleManufacturing conditions Mechanochemical

synthesisMembrane separation Mesoporous structure

Metaborate hydrates Metal fuel Metals MethanolysisMg Mg-Ni eutectic alloy Microcalorimetry MicroreactorMicrostructure Microwave Modeling Modified impregnation

methodMontmorillonite Multiwalled carbon

nanotubesNNa2O NaBH4 NaBH4 hydrolysis NaBH4 recyclingNaBH4-air battery NaBO2 conversion rate NaBO2-H2O binary phase

diagramNano Co-La-Zr-B

Nanoclusters Nanocomposites Nanofiber composite(s) NanofiltrationNanoflowers Nanoparticles Nanostructural transition NanostructureNickel Nickel boride Nickel catalyst Nickel foam (support)Nickel-boride Nickel-ruthenium based

catalystNi-Fe-B catalyst NIH image

Ni-Ru catalyst Non-crystalline structure Numerical simulationOo-CNTs OxidationPPd/C Performance loss Phase diagram Phase transformationPhosphine Plasma Platinum Poly(p-xylylene)Polycarbonate membrane Polyethylene glycol Polymer Polymer-derived

ceramics

Porous carbon films Porous diffuser Porous Fe-Co-B catalyst Porous SiO2

Portable applications Portable power Potassium borohydride Potentiometry

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Powders Power generation Power management (system)

Pt

Pt catalyst Pt/C catalyst Pt/LiCoO2 PtRu-supported catalystsPulse laser deposition PVDF Pyridinium dicationsQQuantitative determination

Quaternary amorphous nanoalloy

RRaney metals Rate constant Reaction engineering Reaction temperatureReactor bottom geometry Recycle (ability) Recycling process RegenerationReused nickel-ruthenium (bimetallic) catalysts

Reutilization Rhodium porphyrin Ru catalyst

Ru dispersion Ru/C catalyst Ru-promoted sulphated zirconia

Ruthenium

Ruthenium (III) acetylacetonate

Ruthenium nanoparticles Ruthenium oxide

SS.S. supported Co catalyst

Sb incorporated TiO2 Self-hydrolysis Semicontinuous reactor

Silicon carbonitride SiO2 support SLS/SFS Small scale deviceSn Sodium borate(s)

hydratedSodium borohydride Sodium borohydride

formationSodium borohydride recovery

Sodium metaborate Sodium polyacrylate Sodium tetraborate

Sodium tetrahydroborate Solid sodium borohydride

Solid-liquid equilibria Solid-state

Solid-state hydrolysis Solid-state(phase) reaction

Solvent effect Solvothermal

Spent fuels Spontaneous hydrolysis Steam Storage solutionStructured catalyst Sudden hydrogen

demandSuper adsorbent polymer Supported catalyst

Supported Co catalyst Supported Ru catalyst Surface alloying Surface areaSynergistic effect SynthesisTTEM Ternary catalyst Tetrachloronickelate (II)

anionTetrahydrofuran

Thermal analysis Thermochemical (method)

Thermochemical conditions

Thermodynamics

Thin film(s) Transition metal Transport process TransportabilityTrimethylphosphiteUUnderwater vehicle Unmanned aerial vehicle

(UAV)VViscoelestic propertiesWWater dispersible Water handling Water vapor hydrolysis Water-methanol mixturesWet chemical reduction processXX-ray absorption spectroscopy

X-ray diffraction (characterization)

X-ray photoelectron spectroscopy

YYieldZZeolite

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