Hydrogen generation from NaBH_(4) for portable proton exchange membrane fuel cell

Sodium borohydride(NaBH_(4)) is considered as the most potential hydrogen storage material for portable proton exchange membrane fuel cells(PEMFC)because of its high theoretical hydrogen capacity.However,the slow and poor kinetic stability of hydrogen generation from NaBH_(4) hydrolysis limits its application.There are two main factors influencing the kinetics stability of hydrogen generation from NaBH_(4).One factor is that the alkaline byproducts(NaBO_(2)) of the hydrolysis reaction can increase the pH of the solution,thus inhibiting the reaction process.It mainly happens in the NaBH_(4) solution hydrolysis system.Another factor is that the monotonous increase in reaction temperature leads to uncontrollable and unpredictable hydrolysis rates in the solid NaBH_(4) hydrolysis system.This is due to the excess heat generated from this exothermic reaction in the initial reaction of NaBH_(4) hydrolysis.In this perspective,we summarize the latest research progress in hydrogen generation from NaBH_(4) and emphasize the design principles of catalysts for hydrogen generation from NaBH_(4) solution and solid state NaBH_(4).The importance of carbon as catalyst support material for NaBH_(4) hydrolysis is also highlighted.

Defect engineering of ternary Cu-In-Se quantum dots for boosting photoelectrochemical hydrogen generation

Heavy-metal-free ternary Cu–In–Se quantum dots(CISe QDs)are promising for solar fuel production because of their low toxicity,tunable band gap,and high light absorption coefficient.Although defects significantly affect the photophysical properties of QDs,the influence on photoelectrochemical hydrogen production is not well understood.Herein,we present the defect engineering of CISe QDs for efficient solar-energy conversion.Lewis acid–base reactions between metal halide–oleylamine complexes and oleylammonium selenocarbamate are modulated to achieve CISe QDs with the controlled amount of Cu vacancies without changing their morphology.Among them,CISe QDs with In/Cu=1.55 show the most outstanding photoelectrochemical hydrogen generation with excellent photocurrent density of up to 10.7 mA cm-2(at 0.6 VRHE),attributed to the suitable electronic band structures and enhanced carrier concentrations/lifetimes of the QDs.The proposed method,which can effectively control the defects in heavy-metal-free ternary QDs,offers a deeper understanding of the effects of the defects and provides a practical approach to enhance photoelectrochemical hydrogen generation.

Polar O-Co-P Surface for Bimolecular Activation in Catalytic Hydrogen Generation

Boron hydrides release an abundant amount of hydrogen in the presence of a suitable catalyst.Accelerating bimolecular activation kinetics is the key to designing cost-effective catalysts for borohydride hydrolysis.In this study,the bimolecular activation of a polar O-Co-P site demonstrated superior hydrogen-generation kinetics(turnover frequency,TOF=37 min−1,298 K)and low activation energy(41.0 kJ mol^(−1))close to that of noble-metal-based catalysts.Through a combination of experiments and theoretical calculations,it was revealed that the activated dangling oxygen atom in the Co–O precursor effectively replaced via surface-phosphorization because of strong electronic interactions between the dangling oxygen and P atoms.This substitution modulated the local coordination environment and electronegativity around the surface Co sites and formed a new polar O-Co-P active site for optimizing the activation kinetics of ammonia borane and water.This strategy based on bimolecular activation may create new avenues in the field of catalysis.

Hydrogen generation from polyvinyl alcohol-contaminated wastewater by a process of supercritical water gasification

Gasification of polyvinyl alcohol （PVA）-contaminated wastewater in supercritical water （SCW） was investigated in a continuous flow reactor at 723-873 K, 20-36 MPa and residence time of 20-450 s. The gas and liquid products were analyzed by GC/TCD, and TOC analyzer. The main gas products were H2, CH4, CO and CO2. Pressure change had no significant influence on gasification efficiency. Higher temperature and longer residence time enhanced gasification efficiency, and lower temperature favored the production of H2. The effects of KOH catalyst on gas product composition were studied, and gasification efficiency were analyzed. The TOC removal efficiency （RTOC）, carbon gasification ratio （RCG） and hydrogen gasification ratio （RHG） were up to 96.00%, 95.92% and 126.40% at 873 K and 60 s, respectively, which suggests PVA can be completely gasified in SCW. The results indicate supercritical water gasification for hydrogen generation is a promising process for the treatment ofPVA wastewater.

Hydrogen generation from methanolysis of sodium borohydride over Co/Al_2O_3 catalyst

Co/Al2O3 catalyst is prepared with an impregnation-chemical reduction method and used to catalyze the methanolysis of sodium borohydride （NaBH 4） for hydrogen generation.At solution temperature of 0 C,the methanolysis reaction can be effectively accelerated using Co/Al2O3 catalyst and provide a desirable hydrogen generation rate,which makes it suitable for applications under the circumstance of low environmental temperature.The byproduct of methanolysis reaction is analyzed by X-ray diffraction （XRD） and Fourier transform infrared spectroscopy （FTIR）.The characterization results indicate that methanol can be easily recovered after methanolysis reaction by hydrolysis of the methanolysis byproduct,NaB（OCH 3） 4.The catalytic activity of Co/Al2O3 towards NaBH 4 methanolysis can be further improved by appropriate calcination treatment.The catalytic methanolysis kinetics and catalyst reusability are also studied over the Co/Al2O3 catalyst calcined at the optimized temperature.

Co-CoO_x supported onto TiO_(2) coated with carbon as a catalyst for efficient and stable hydrogen generation from ammonia borane

Ammonia borane(AB) can be catalytically hydrolyzed to provide hydrogen at room temperature due to its high potentaial for hydrogen storage. Non-precious metal heterogeneous catalysts have broad application in the field of energy catalysis. In this article, catalysts precursor is obtained from Co-Ti-resorcinol-formaldehyde resin by sol–gel method. Co/TiO_(2)@N-C(CTC) catalyst is prepared by calcining the precursor under high temperature conditions in nitrogen atmosphere. Co-CoO_x/TiO_(2)@N-C(COTC) is generated by the controllable oxidation reaction of CTC. The catalyst can effectively promote the release of hydrogen during the hydrolytic dehydrogenation of AB. High hydrogen generation at a specific rate of 5905 m L min^(-1) g_(Co)^(-1) is achieved at room temperature. The catalyst retains its 85% initial catalytic activity even for its fifth time use in AB hydrolysis. The synergistic effect among Co, Co_(3)O_(4) and TiO_(2) promotes the rate limiting step with dissociation and activation of water molecules by reducing its activation energy. The applied method in this study promotes the development of non-precious metals in catalysis for utilization in clean energy sources.

Effect of doped Ni-Bi-B alloy on hydrogen generation performance of Al-InCl3

In this work,Ni-Bi-B alloy has been synthesized via chemical synthesis method.A new kind of Al-InCl3-(Ni-Bi-B)composite has been prepared by high energy mechanical ball grinding A1 powder with additives.Results show that the doped Ni-Bi-B alloy can significantly improve the hydrogen generation performance of Al-InCl3 and the catalytic activity is enhanced with the increasing content of Bi in Ni-Bi-B alloy.Under optimal conditions,the hydrogen generation yield and conversion yield of Al-InCl3-(Ni-Bi-B)reached1196.8 mL g^-1 and 100.0%at room temperature,respectively.Mechanism study shows five kinds of active sites,such as the fresh surface/defect of Al particle,Al-AlCl3,Al-In,Al-Bi/B and Al-Ni/B produced during the ball milling process.Their synergistic effect enhances the hydrogen generation performance of AlInCl3-(Ni-Bi-B)remarkably.In general,the proposed Al-InCl3-(Ni-Bi-B)composite is possible to serve as hydrogen generation material for fuel cells.

Oxalic Acid Promoted Hydrolysis of Sodium Borohydride for Transition Metal Free Hydrogen Generation

We reported an inexpensive and high-efficiency hydrogen generation method from NaBH4 hydrolysis promoted by oxalic acid.NaBH4 and H2C2O4 were premixed and hydrogen generation was initiated by adding water into the solid mixture.H2C2O4 was selected as the acid promotor due to its solid state and low mass per proton.The effect of reactant ratio on the hydrogen yield and hydrogen storage density was investigated.With optimized reactant ratio,high gravimetric hydrogen storage up to 4.4wt%based on all the reactants can be achieved with excellent hydrogen generation kinetics.

Boosting electrocatalytic hydrogen generation by a renewable porous wood membrane decorated with Fe-doped NiP alloys

Porous biomass electrodes have emerged as a critical material for electrocatalytic hydrogen evolution reaction(HER).However,most approaches for synthesizing porous electrodes from biomass require high energy consumption,which is resulted from the smash of biomass and the undergoing of serial assembly.Herein,a self-supported wood-derived"breathable"membrane is utilized directly as electrodes for highefficient HER via an assembly of Fe-doped NiP alloys.The well-designed hierarchical porous structures in natural wood membrane(NWM)are unusually beneficial for electrolytes accessibility and hydrogen gas removal.The obtained wood-derived membrane exhibits a high electrocatalytic activity and good cycling durability in acidic and alkaline electrolytes.Remarkably,the Fe_(0.074) NiP alloys/NWM electrode affords a large current density of 100 m A cm^(-2) at extremely low overpotentials of 168 mV in acidic electrolyte and174 m V in alkaline electrolyte.Density functional theory calculations unveil that the Fe atom doped in NiP alloys can create much more charge accumulation around Fe and Ni active sites,which helps decrease the △GH_(*)and △G_(H2O)and significantly promote the HER process.This new insight will promote further explorations of economic,high-efficient,and biodegradable wood-derived electrocatalysts for HER.

Mesoporous cadmium bismuth niobate(CdBi2Nb2O9)nanospheres for hydrogen generation under visible light

Herein, we report visible light active mesoporous cadmium bismuth niobate（CBN） nanospheres as a photocatalyst for hydrogen（H） generation from copious hydrogen sulfide（HS）. CBN has been synthesized by solid state reaction（SSR） and also using combustion method（CM） at relatively lower temperatures.The as-synthesized materials were characterized using different techniques. X-ray diffraction analysis shows the formation of single phase orthorhombic CBN. Field emission scanning electron microscopy and high resolution-transmission electron microscopy showed the particle size in the range of.5–1 μm for CBN obtained by SSR and 50–70 nm size nanospheres using CM, respectively. Interestingly, nanospheres of size 50–70 nm self assembled with 5–7 nm nanoparticles were observed in case of CBN prepared by CM.The optical properties were studied using UV–visible diffuse reflectance spectroscopy and showed band gap around.0 eV for SSR and 3.1 eV for CM. The slight shift in band gap of CM is due to nanocrystalline nature of material. Considering the band gap in visible region, the photocatalytic activity of CBN for hydrogen production from HS has been performed under visible light. CBN prepared by CM has shown utmost hydrogen evolution i.e. 6912 μmol/h/0.5 g which is much higher than CBN prepared using SSR.The enhanced photocatalytic property can be attributed to the smaller particle size, crystalline nature,high surface area and mesoporous structure of CBN prepared by combustion method. The catalyst was found to be stable, active and can be utilized for water splitting.

Integrated Ni-P-S nanosheets array as superior electrocatalysts for hydrogen generation

Searching for efficient and robust non-noble electrocatalysts for hydrogen generation is extremely desirable for future green energy systems.Here, we present the synthesis of integrated Ni-P-S nanosheets array including Ni_2P and NiS on nickel foam by a simple simultaneous phosphorization and sulfurization strategy. The resultant sample with optimal composition exhibits superior electrocatalytic performance for hydrogen evolution reaction(HER) in a wide pH range. In alkaline media, it can generate current densities of 10, 20 and 100 mA cm^(-2) at low overpotentials of only-101.9,-142.0 and-207.8 mV with robust durability. It still exhibits high electrocatalytic activities even in acid or neutral media. Such superior electrocatalytic performances can be mainly attributed to the synergistic enhancement of the hybrid Ni-P-S nanosheets array with integration microstructure. The kind of catalyst gives a new insight on achieving efficient and robust hydrogen generation.

Enhancement in solar hydrogen generation efficiency using InGaN photoelectrode after surface roughening treatment with nano-sized Ni mask

A significant enhancement in solar hydrogen generation efficiency has been achieved by inductive coupled etching （ICP） surface roughening treatment using nano-sized nickel mask. As much as 7 times improvement of photocurrent is demonstrated in comparison with a planar one fabricated from the same parent wafer. Under identical illumination conditions in HBr solution, the incident photon conversion efficiency （IPCE） shows an enhancement with a factor of 3, which even exceed 54% at 400 nm wavelength. We believe the enhancement is attributed to several facts including improvement in absorption, reacting area, carder localization and carrier lifetime.

Experimental Study of Plasma Under-liquid Electrolysis in Hydrogen Generation

The application and characteristics of relatively big volume plasma produced with cathodic glow discharges taking place across a gaseous envelope over the cathode which was dipped into electrolyte in hydrogen generation were studied. A critical investigation of the influence of methanol concentration and voltage across the circuit on the composition and power consumption per cubic meter of cathode liberating gas was carried out. The course of plasma under-liquid electrolysis has the typical characteristics of glow discharge electrolysis. The cathode liberating gas was in substantial excess of the Faraday law value. When the voltage across the circuit was equal to 550 V,the volume of cathodic gas with sodium carbonate solution was equal to 16.97 times the Faraday law value. The study showed that methanol molecules are more active than water molecules. The methanol molecules were decomposed at the plasma-catholyte interface by the radicals coming out the plasma mantle. Energy consumption per cubic meter of cathodic gases (WV) decreased while methanol concentration of the electrolytes increased. When methanol concentration equaled 5% (-),WV was 10.381×103 kJ/m3,less than the corresponding theoretic value of conventional water electrolysis method. The cathodic liberating gas was a mixture of hydrogen,carbon dioxide and carbon monoxide with over 95% hydrogen,if methanol concentration was more than 15% (-). The present research work revealed an innovative application of glow discharge and a new highly efficient hydrogen generation method,which depleted less resource and energy than normal electrolysis and is environmentally friendly.

Oxalic Acid Promoted Hydrolysis of Sodium Borohydride for Transition Metal Free Hydrogen Generation

We reported a low cost,high efficiency hydrogen generation method from NaBH4 hydrolysis promoted by oxalic acid.NaBH4 and H2C2O4 were premixed and hydrogen generation was initiated by adding water into the solid mixture.H2C2O4 was selected as the acid promotor due to its solid state and low mass per proton.The effect of reactant ratio on the hydrogen yield and hydrogen storage density was investigated.With optimized reactant ratio,high gravimetric hydrogen storage up to 4.4wt% based on all the reactants can be achieved with excellent hydrogen generation kinetics.

Enhanced hydrogen generation from hydrolysis of MgLi doped with expanded graphite

Hydrolysis of Mg-based materials is considered as a potential means of safe and convenient real-time control of H_(2)release,enabling efficient loading,discharge and utilization of hydrogen in portable electronic devices.At present work,the hydrogen generation properties of MgLi-graphite composites were evaluated for the first time.The MgLi-graphite composites with different doping amounts of expanded graphite(abbreviated as EG hereinafter)were synthesized through ball milling and the hydrogen behaviors of the composites were investigated in chloride solutions.Among the above doping systems,the 10 wt.%EG-doped MgLi exhibited the best hydrogen performance in MgCl_(2)solutions.In particular,the 22 h-milled MgLi-10 wt.%EG composites possessed both desirable hydrogen conversion and rapid reaction kinetics,delivering a hydrogen yield of 966 mL H_(2)g^(-1)within merely 2 min and a maximum hydrogen generation rate of 1147 mL H_(2)min^(-1)g^(-1),as opposed to the sluggish kinetics in the EG-free composites.Moreover,the EG-doped MgLi showed superior air-stable ability even under a 75 RH%ambient atmosphere.For example,the 22 h-milled MgLi-10 wt.%EG composites held a fuel conversion of 89%after air exposure for 72 h,rendering it an advantage for Mg-based materials to safely store and transfer in practical applications.The similar favorable hydrogen performance of MgLi-EG composites in(simulate)seawater may shed light on future development of hydrogen generation technologies.

Hydrogen Generation by Splitting H2O Molecule on the Pt6Cu Cluster

Seven reaction paths for hydrogen generation from water molecule with Pt6Cu cluster are identified, based on the density functional theory with exchange-correlation functional in Becke＇s three-parameter form. The complex structures of the reactant H2O@Pt6Cu and the structures of the products H2＋O@Pt6Cu and H＋OH@Pt6Cu on various adsorption sites of Pt6Cu cluster are optimized and the energy stability of the structures is confirmed by frequency analysis. The geometries of the transition states and the intrinsic reaction coordinate are also determined at the same theoretical level. The energy barrier for each reaction is calculated. The results demonstrate that the Pt6Cu cluster can abstract one H atom from H2O molecule with one step reaction by overcoming a moderate energy barrier. These findings can be helpful for understanding the mechanism to produce hydrogen from a water molecule with Pt6Cu cluster.

A novel nanoporous Mg-Li material for efficient hydrogen generation

Hydrogen generation material is a new kind of energy material that can supply hydrogen by reacting with water and is drawing more and more attention with the development of hydrogen economy. In this study, a novel nanoporous magnesium-lithium material prepared by a physical vapor deposition method exhibits an excellent hydrogen generation property. It generates hydrogen efficiently and quickly with saltwater, reaching a hydrogen generation amount of 962 mL g^(-1) and hydrogen generation rates of 60 mL g^(-1)min^(-1), 109 mL g^(-1)min^(-1),256 mL g^(-1)min^(-1) and 367 mL g^(-1)min^(-1) at 0 ℃, 25 ℃, 35 ℃ and 50 ℃, respectively. The nanoporous magnesium-lithium material is composed of a solid solution phase with a magnesium-lithium atomic ratio of 17:3. By synchrotron radiation analysis, the sizes of the nanopores are in the range of 100 nm ~ 600 nm with an average size of 280 nm, and the porosity is calculated to be ~42.4%. The improved hydrogen generation property is attributed to the nanoporous structure with a high specific surface area, and the addition of lithium element which acts as active sites in hydrogen generation process.

Surface Modification of Titanium Oxide by Indium for Efficient PhotocatalyticHydrogen Generation

We fabricated indium ion-modified TiO2nanoparticles. The results revealed that indium presents on TiO2surface in the form of fixed ion, by coordinating with hydroxyl groups or terminal oxygen atoms at the surface of TiO2, which resulted in smaller grain size, larger surface area, and mesoporous structure relative to pure titanium dioxide. Compared with pure TiO2, indium ion-modified TiO2showed great enhancement of photocatalytic activity to hydrogen generation. Owing to electronic capture capability of indium, the excited electrons can rapidly transfer from TiO2conduction band to indium, resulting in the separation of electron-hole pairs. The optimal H2 evolution rate was 277.8 mmol·g-1·h-1, which was about 23 times higher than that of Degussa P25.

Phytic acid-derivative Co_(2)B-CoPO_x coralloidal structure with delicate boron vacancy for enhanced hydrogen generation from sodium borohydride

Application of transition metal boride(TMB) catalysts towards hydrolysis of NaBH_(4) holds great significance to help relieve the energy crisis. Herein, we present a facile and versatile metal-organic framework(MOF) assisted strategy to prepare Co_(2)B-CoPO_x with massive boron vacancies by introducing phytic acid(PA) cross-linked Co complexes that are acquired from reaction of PA and ZIF-67 into cobalt boride. The PA etching effectively breaks down the structure of ZIF-67 to create more vacancies, favoring the maximal exposure of active sites and elevation of catalytic activity. Experimental results demonstrate a drastic electronic interaction between Co and the dopant phosphorous(P), thereby the robustly electronegative P induces electron redistribution around the metal species, which facilitates the dissociation of B-H bond and the adsorption of H_(2)O molecules. The vacancy-rich Co_(2)B-CoPO_x catalyst exhibits scalable performance, characterized by a high hydrogen generation rate(HGR) of 7716.7 m L min^(-1)g^(-1) and a low activation energy(Ea) of 44.9 k J/mol, rivaling state-of-the-art catalysts. This work provides valuable insights for the development of advanced catalysts through P doping and boron vacancy engineering and the design of efficient and sustainable energy conversion systems.

Ultrathin oxygen-containing graphdiyne wrapping CoP for enhanced electrocatalytic hydrogen generation

Graphdiyne(GDY)is fascinating in the construction of efficient and stable catalysts,but their performance is still somewhat restricted due to GDY’s thicker layers,as well as hydrophobic and relatively chemically inert surfaces.Herein,via oxidationexfoliation-reduction strategy,the self-supported electrode material of CoP nanosheets with ultrathin oxygen-containing GDY wrapping(CoP@RGDYO)for effective HER is constructed.The wrapping of ultrathin oxygen-containing GDY promotes charge transfer,improves the surface property,and enhances the acid and alkali resistance as well as the structural stability of the catalyst.As a result,CoP@RGDYO shows enhanced activity and stability in both acidic and alkaline media.Especially,it exhibits a low overpotential of 86 mV and exceptional stability under a 14000-cycle cyclic voltammetry scanning in alkaline media.This work provides new ideas for the design of GDY hybrid materials and the preparation of high-efficiency catalysts.