Interface Engineering and Anion Engineering of Mo-Based Heterogeneous Electrocatalysts for Hydrogen Evolution Reaction

Development and utilization of hydrogen energy is an effective way to achieve carbon neutrality,only hydrogen production through electrolytic water splitting meets the goal of zero carbon emission.To facilitate the large-scale commercialization of water splitting devices,the development of highly efficient and low-cost catalysts to reduce the energy consumption is essential.MoS_(2)has been regarded as a promising electrocatalyst to replace platinum in hydrogen evolution reaction due to its low price and unique 2D layered structure.However,the poor conductivity and inert basal planes of MoS_(2)limited its wide-spread application.Recently,researches have demonstrated that the conductivity and active sites of MoS_(2)can be improved by heteroatoms doping or constructing of heterogeneous structures.In this review,the recent progress of Mo-based catalysts are summarized centered on MoS_(2)based on interface engineering and anion engineering,including MoS_(2)–MoO_(2),MoS_(2)–Mo_(2)C,MoS_(2)–MoN_(x),MoS_(2)–MoP,and MoS_(2)–MoSe_(2).The preparation method,structure,and performance of the catalysts are introduced and the possible mechanism behind the improved catalytic activity are revealed to give readers an overall comprehension on the progress of the Mo-based electrocatalysts for hydrogen evolution reaction.In addition,an outlook on future opportunities and development directions of Mo-based catalysts are proposed to facilitate the development of Mo-based catalysts for hydrogen production.

Multifunctional Dy(Ⅲ)doped di-calcium silicate array for boosting display and forensic applications

Latent fingerprints（LFPs） are the major physical evidences for the identification of individuals during crime spot investigation. Till date, numerous methods were followed to visualize LFPs. However, simple,accurate, and cost-effective method has wide scope in advanced forensic field. In our work, Ca2 SiO4：Dy^（3＋）nanopowders（NPs） were fabricated via solution combustion route. The optimized sample was employed for the visualization of overlapped LFPs by the cost effective powder dusting method. The obtained results reveals the complete three levels of ridge characteristics with high sensitivity, reproducibility,selectivity, and reliability on various complex surfaces. The photoluminescence（PL） spectra consist of intense peaks at ～ 480 and 574 nm owing to ~4 F（9/2） →~6 H（15/2） and ~4 F（9/2）→~6 H（13/2） 4 f transitions of Dy3＋ ions,respectively. The photometric properties confirm that the samples exhibit intense white emission with high color purity. Therefore, the prepared NPs could be a definitive choice as an advanced luminescent NPs for forensic, solid state lighting and portable FED devices.

Rational design of monovalent ions （Li,Na,K） co-doped ZnAl2O4:Eu3+ nanocrystals enabling versatile robust latent fingerprint visualization

Alkali metal ions(M+ = Na+,Li+,K+) co-doped ZnAl2O4:Eu3+(5 mol%)(ZAE) nanopowders(NPs) were prepared via solution combustion route using Mimosa pudica(MP) leaves extract as a fuel. PXRD results of co-doped samples enhance the crystallinity and grain growth. Photoluminescence(PL) of the prepared ZAE and ZAE:M+(M+ = Na+, Li+, K+) NPs shows intense emission peaks in the range of 550-750 nm and ascribed to 5D0→7FJ(J=0-4) transitions of Eu3+ ions, respectively. A 2-fold enhancement in PL intensity was observed in Li+ co-doped samples. The optimized ZnAl2O4:Eu3+(5 mol%), Li+(1 wt%)(ZAEL)NPs were used to visualize LFPs on various porous, semi-porous and non-porous surfaces through robust powder dusting technique. The visualized latent fingerprints(LFPs) reveal well defined level 1-3 ridge characteristics under several tests such as fingerprint aging and fresh water treatment for various time durations. The obtained results clearly evidence that the prepared NPs are quite useful for multifunctional applications such as advanced forensic and solid state lightning.

Enhanced photocatalytic activities of silicon nanowires/graphene oxide nanocomposite:Effect of etching parameters

Homogeneous and vertically aligned silicon nanowires(SiNWs)were successfully fabricated using silver assisted chemical etching technique.The prepared samples were characterized using scanning electron microscopy,transmission electron microscopy and atomic force microscopy.Photocatalytic degradation properties of graphene oxide(GO)modified SiNWs have been investigated.We found that the SiNWs morphology depends on etching time and etchant composition.The SiNWs length could be tuned from 1 to 42μm,respectively when varying the etching time from 5 to 30 min.The etchant concentration was found to accelerate the etching process;doubling the concentrations increases the length of the SiNWs by a factor of two for fixed etching time.Changes in bundle morphology were also studied as function of etching parameters.The SiNWs diameter was found to be independent of etching time or etchant composition while the size of the SiNWs bundle increases with increasing etching time and etchant concentration.The addition of GO was found to improve significantly the photocatalytic activity of SiNWs.A strong correlation between etching parameters and photocatalysis efficiency has been observed,mainly for SiNWs prepared at optimum etching time and etchant concentrations of 10 min and 4:1:8.A degradation of92%was obtained which further improved to 96%by addition of hydrogen peroxide.Only degradation efficiency of 16%and 31%has been observed for bare Si and GO/bare Si samples respectively.The obtained results demonstrate that the developed SiNWs/GO composite exhibits excellent photocatalytic performance and could be used as potential platform for the degradation of organic pollutants.

Microstructure and electrical transport mechanisms of the Ca-doped LaMnO_(3) films grown on MgO substrate

La_(0.7)Ca_(0.3)MnO_(3)(LCMO)thin films have been grown on MgO substrate using the metal organic deposition process.The lattice mismatch between LCMO and MgO is relatively large around 8.14% imposing large inplane-tensile strain and out-of-plane-compressive strain on the film.Hence the structural,microstructural and electrical properties have been found to be strongly correlated to the strain degree and relaxation.Cross-section transmission electron microscopy observations demonstrate the presence of microstructural defects due to the large lattice mismatch between the LCMO and MgO.In addition to structural and microstructural defects,X-ray diffraction and Raman spectroscopy measurements show the existence of a minor phase of MnO in the film.Magnetization versus temperature measurement show a relatively low Curie temperature around 75 K.The electrical behavior is found to be semiconducting over a large temperature interval.The electrical transport mechanisms have been investigated using the small polaron hopping and variable range hopping models and correlated to their microstructural properties.