Promoted hydrolysis performances and mechanism of Si-NaBH4-AlCl_(3) in deionized water

Si-based hydrolysis material system can be used in mobile/portable hydrogen source applications connected to fuel cells but is limited by alkaline solutions.In the present research,we reported an acid/alkaline free hydrolysis systemcombining siliconwith NaBH4.Sampleswith different ratios between Si and NaBH4 are prepared via high energy ball milling and hydrolyzed in deionized water at different temperatures.Synergetic effect between silicon and NaBH4was found in the hydrolysis process.2Si-NaBH4 sample displays the best hydrolysis performances with the hydrogen yield of 1594 ml·g^(−1) in deionized water at 70℃.Thereafter,AlCl3 is added into the 2Si-NaBH4 sample to further improve its comprehensive properties.The effect of AlCl3 content and promotion mechanism of the reaction are explored.2Si-NaBH4-5 wt% AlCl3 sample shows a significant improvement with a high hydrogen yield of 1689 ml·g^(−1) in deionized water at 70℃ and a corresponding conversion rate of 95.8%,indicating that the Si-NaBH4-AlCl3 composite is promising to be a hydrogen source in applications of mobile/portable fuelcell-powered facilities.

Size and near-surface engineering in weak-oxidative confined space to fabricate 4 nm L1_(0)-PtCo@Pt nanoparticles for oxygen reduction reaction

The near-surface structure of the Pt-based alloy including the surface and subsurface structures is prominent to their electrocatalytic performance.Modulating the near-surface structure of PtCo intermetallics with small particle size could efficiently optimize the binding force between Pt and oxygen and finally enhance its oxygen reduction reaction(ORR)performance.Here we simultaneously achieve the size controlling and surface modulation of intermetallic nanoparticles(NPs)in a weak-oxidative confined space with abundant uncoordinated oxygen atoms.1–2 atomic layers of concave Pt-rich surface were successfully constructed on 4 nm L1_(0)-PtCo core after removing Co–O species which is derived from the segregation of the subsurface Co to the surface induced by the uncoordinated oxygen atoms.Owing to the elaborate structure,PtCo-1000/C catalyst shows significant improvement in both activity(1.290 A∙mg_(Pt)^(−1)and 1.529 mA∙cm_(Pt)^(−2) at 0.9 V vs.reversible hydrogen electrode(RHE))and stability(85.2%of initial mass activity after accelerated degression tests(ADTs))even the production is scaled up to gram level.Density functional theory calculations suggest that the cave Pt site optimizes the protonation of*O,which finally boosts the ORR performance.

Hydrolysis enhancing mechanisms of Mg-based alloys/hydrides from perspectives:Electrochemical corrosion,active sites,mass transfer,and kinetics

Hydrogen energy is considered to be an ideal new energy carrier in the 21st century due to its clean,environmentally friendly,renewable characteristics and high energy density.The generation of hydrogen by hydrolysis of Mg-based alloys/hydrides has attracted extensive attention attributed to the high hydrogen yield,environmentally-benign by-products,high crust abundance,and well-developed industrial production of Mg.However,in the hydrolysis process of Mg or MgH_(2)to generate hydrogen,the formed Mg(OH)_(2)passivation layer attaches to the surface of the active materials to prevent the reaction from continuing.To improve the hydrolysis performance,a series of methods have been put forward.In this paper,focusing on the mechanisms of hydrogen generation by hydrolysis of Mg-based alloys/hydrides,we summarize the recent research progress from four different perspectives:electrochemical corrosion promotion by constructing galvanic cells,active sites increment by refining the particles,mass transfer enhancement by breaking Mg(OH)_(2)and corresponding kinetic improvement.