Hydrolysis hydrogen production mechanism of Mg10Ni10Ce alloy surface modified by SnO_(2) nanotubes in different aqueous systems

(Mg-10wt%Ni)-10wt%Ce(Mg10Ni10Ce)was ball-milled with SnO_(2)nanotubes and Mg10Ni10Ce-xSnO_(2)(x¼0,5,10 and 15 wt%)composites have been prepared.The phase compositions,microstructures,morphologies and hydrolysis H2 generation performance in different aqueous systems(distilled water,tap water and simulated seawater)have been investigated and the corresponding hydrolysis mechanism of Mg10Ni10Ce and Mg10Ni10CeeSnO_(2)has been proposed.Adding a small amount of SnO_(2)nanotubes can significantly enhance the hydrolysis reaction of Mg10Ni10Ce,especially the initial hydrolysis kinetics and the final H_(2) generation yield.Unfortunately,the Mg10Ni10Ce-xSnO_(2)hardly reacts with distilled water at room temperature.The hydrolysis reaction rate of Mg10Ni10Cee5SnO_(2)composite in tap water is still very slow with only 17.3%generation yield after 1 h at 303 K.Fortunately,in simulated seawater(3.5 wt%NaCl solution),the hydrolytic H2 generation behavior of the Mg10Ni10Cee5SnO_(2)composite has been greatly improved,which can release as high as 468.6 mL g^(-1 )H_(2) with about 60.9%generation yield within 30 s at 303 K.The Cl destroys the passivation layer on MgeNieCe alloy surface and the added SnO_(2)nanotubes accelerate the hydrolysis reaction rate and enhance the H2 generation yield.The Mg10Ni10Cee5SnO_(2)composite can rapidly generate a large amount of H2 in simulated seawater in a short time,which is expected to be applied on portable H2 generators in the future.

H_2 generation kinetics/thermodynamics and hydrolysis mechanism of high-performance La-doped Mg-Ni alloys in Na Cl solution——A large-scale and quick strategy to get hydrogen

In this work,La-doped Mg-Ni multiphase alloys were prepared by resistance melting furnace(RMF)and then modified by high-energy ball milling(HEBM).The hydrolysis H_(2) generation kinetics/thermodynamics of prepared alloys in Na Cl solutions have been investigated with the help of nonlinear and linear fitting by Avrami-Erofeev and Arrhenius equations.Combining the microstructure information before and after hydrolysis and thermodynamics fitting results,the hydrolysis H_(2) generation mechanism based on nucleation&growth has been elaborated.The final H_(2) generation capacities of 0La,5La,10La and 15 La alloys are 677,653,641 and 770 m L·g^(-1)H_(2) in 240 min at291 K,respectively.While,the final H_(2) generation capacities of HEBM 0La,5La,10La and 15 La alloys are 632,824,611 and 653 m L·g^(-1)H_(2) in 20 min at 291 K,respectively.The as-cast 15La alloy and HEMB 5La alloy present the best H_(2) production rates and final H_(2) production capacities,especially the HEBM 5La can rapidly achieve high H_(2) generation capacity(670 and 824 m L·g^(-1)H_(2) )at low temperature(291 K)within short time(5 and 20 min).The difference between the H_(2) generation capacities is mainly originated from the initial nucleation rate of Mg(OH)_(2) and the subsequent processes affected by the microstructures and phase compositions of the hydrolysis alloys.Relative low initial nucleation rate and fully growth of Mg(OH)_(2) nucleus are the premise of high H_(2) generation capacity due to the hydrolysis H_(2) generation process consisted by the nucleation,growth and contacting of Mg(OH)_(2) nucleus.To utilization H_(2) by designing solid state H_(2) generators using optimized Mg-based alloys is expected to be a feasible H_(2) generation strategy at the moment.

Improvement in potassium ion batteries electrodes: Recent developments and efficient approaches

Demand for efficient and continuous application for high-grid energy storage systems involves the study towards novel battery technologies. Hence, considering the vast naturally available resources of potassium all over the world and its encouraging intercalation chemistries, it has recently enticed attention in electrochemical energy storage industry in the form of potassium ion batteries (PIBs). The major factor in this K+ based battery, is to develop efficient approaches to manufacture electrode substance to intercalate its big size potassium ions with considerable voltage, kinetics, charge/discharge capacity, capacity retention, cost, etc. This study contributes in the recent developments of anode and cathode materials for PIBs, including several electrode materials in regards to synthesis, structure, electrochemical performance, and K-storage mechanisms. Finally, the review contributes to provide helpful sources for the increasing number of scientists working in this industry regarding its critical issues and challenges and also to indicate the future direction of electrode materials in PIBs.

Full-spectrum responsive photocatalytic activity via non-noble metal Bi decorated mulberry-like BiVO_(4)

Due to its appropriate bandgap(~2.4 e V)and efficient light absorption,bismuth vanadate(Bi VO_(4))shows promising photocatalysis activity.However,the charge carrier recombination and poor electron transmission often induce poor photocatalytic performance.Herein,we report a new method to in-situ synthesize non-noble metal Bi decorated mulberry-like Bi VO_(4)by a two-step calcination process.Comprehensive characterizations reveal that non-noble metal Bi nanoparticles grown in-situ on Bi VO_(4)result in the red-shift of the absorbance edge,greatly extending the light absorption from the ultraviolet into the near-infrared region.The surface plasmon resonance excitation of Bi nanoparticles and synergetic effects between Bi and Bi VO_(4)effectively improve the photocatalytic efficiency and promote the separation of photoinduced electron-hole pairs in mulberry-like Bi VO_(4).Density functional theory(DFT)calculation results further verify that the electrons are transferred from Bi to Bi VO_(4)and the formation of·OH radical in Bi/Bi VO_(4)is attributed to the lower simulated free energy,which supports our experimental outcomes.This work provides a novel strategy to enhance light absorption and promote efficient solar utilization of photocatalysts for practical applications.

Thermoelectric performance enhancement by manipulation of Sr/Ti doping in two sublayers of Ca_(3)Co_(4)O_(9)

Thermoelectric(TE)performance of Ca_(3)Co_(4)O_(9)(CCO)has been investigated extensively via a doping strategy in the past decades.However,the doping sites of different sublayers in CCO and their contributions to the TE performance remain unrevealed because of its strong correlated electronic system.In this work,Sr and Ti are chosen to realize doping at the[Ca_(2)CoO_(3)]and[CoO_(2)]sublayers in CCO.It was found that figure of merit(ZT)at 957 K of Ti-doped CCO was improved 30% than that of undoped CCO whereas 1 at% Sr doping brought about a 150% increase in ZT as compared to undoped CCO.The significant increase in electronic conductivity and the Seebeck coefficient are attributed to the enhanced carrier concentration and spin-entropy of Co^(4+) originating from the Sr doping effects in[Ca_(2)CoO_(3)]sublayer,which are evidenced by the scanning electron microscope(SEM),Raman,Hall,and X-ray photoelectron spectroscopy(XPS)analysis.Furthermore,the reduced thermal conductivity is attributed to the improved phonon scattering from heavier Sr doped Ca site in[Ca_(2)CoO_(3)]sublayer.Our findings demonstrate that doping at Ca sites of[Ca_(2)CoO_(3)]layer is a feasible pathway to boost TE performance of CCO material through promoting the electronic conductivity and the Seebeck coefficient,and reducing the thermal conductivity simultaneously.This work provides a deep understanding of the current limited ZT enhancement on CCO material and provides an approach to enhance the TE performance of other layered structure materials.

Construction of SnS2/SnO2 heterostructures with enhanced potassium storage performance

Increasing attention has been focused on potassium ion batteries(KIBs) as promising energy-sto rage system(ESS) owing to the abundance and low-cost of potassium resources.Here,SnS2/SnO2 hete rostructures were successfully fixed onto stainless steel mesh(SnS2/SnO2/SSM) through a facile two-step hydrothermal method and used as anodes for KIBs.Due to the advantages of SnS2/SnO2 heterostructures and good conductivity of SSM substrate,the SnS2/SnO2/SSM anodes display enhanced electrochemical performance.The SnS2/SnO2/SSM anodes deliver specific capacity of 394 mA h g^-1 at 50 mA g^-1 over 100 cycles,better than SnO2/SSM.Even at 500 mA g^-1 after 250 cycles,high capacity of 155 mA h g^-1 can still be obtained.