Synergism and anion-cation dual chemical substitution in heterostructure sprouted on MXene enable high-efficiency and stable overall water splitting

The exploration of novel,super-potent and low-cost electrocatalysts for water splitting has always been the kernel in the field of renewable sources.Herein,exfoliated Ti_(3)C_(2)T_(x) MXenes work as a substrate to vertically grow polypore N,Ni-Co2P nanoarrays(N,Ni-Co2P@TC)through an in situ interface-growth strategy and subsequent phosphorization and nitridation.The well-defined heterointerfaces with positive and negative ions co-modulation as coupled hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)catalysts for efficient overall water splitting are investigated,which possesses excellent durability even at a large current density(±500 mA cm^(-2)).For HER,suitable H_(2)O∗and H∗absorption energies and accelerated electronic transmission make N,Ni-Co2P@TC display a low overpotential of 27 mV at-10 mA cm^(-2) and Tafel slope of 38 mV dec^(–1) in 1 mol/L KOH.For OER,the synergy of N,Ni-Co2P@TC with selfreconfiguration can give enhanced activity with a low overpotential of 232 mV at 10 mA cm^(-2) and a Tafel slope of 57 mV dec^(–1).Additionally,the excellent bifunctional activity allows easily combining for efficient overall water splitting with a low driving voltage(1.51 V)at 10 mA cm^(-2),and the electrolyzer can be driven by a 1.5 V AAA battery.

Zintl phase compounds AM_2Sb_2(A=Ca,Sr,Ba,Eu,Yb;M=Zn,Cd) and their substitution variants:a class of potential thermoelectric materials

Zintl phase compounds AM2Sb2 （A=Ca, Sr, Ba, Eu, Yb;M=Zn, Cd） is a new class of promising thermoelectrics owing to their intrinsic features in electronic and crystal structure, such as a small or even disappeared band-gap, large density-of-states at the Fermi level, covalently bonded network of M-Sb, as well as the layered stacking by cations A2＋and anionic slabs （M2Sb2）2-. In addi-tion, the rich solid-state chemistry of Zintl phase allows structural modification and chemical substitution to adjust the fundamental transport parameters （carrier concentration, mobility, effective mass, electronic and lattice thermal conductivity） for improving the thermoelectric performance. In the present review, the recent advances in synthesis and thermoelectric characterization of title com-pounds AM2Sb2 were presented, and the effects of alloying or substitution for sites A, M and Sb on the electrical and thermal trans-port were emphasized. The structural disorder yielded by the incorporation of multiple ions significantly increased the thermoelectric figure of merit mainly resulted from the reduction of thermal conductivity without disrupting the carrier transport region in substance. Therefore, alloying or substitution has been a feasible and common route utilized to enhance thermoelectric properties in these Zintl phase compounds, especially for YbZn0.4Cd1.6Sb2 （ZT700 K=1.26）, EuZn1.8Cd0.2Sb2 （ZT650 K=1.06）, and YbCd1.85Mn0.15Sb2 （ZT650 K=1.14）.

Boosting alkaline hydrogen evolution via spontaneous built-in electric field

The electrochemical reaction rate strongly depends on the pH of the solution and the relatively sluggish alkaline hydrogen evolution reaction(HER)process,attributed to alterations in the type of proton donor and binding energy,has consistently presented a significant challenge.Here,we report a new method for boosting alkaline HER via spontaneous built-in electric field strategy employed on cobalt phosphide nanofibers(NFs)electrocatalyst.The anion-cation dual-introduction of V and N on the NFs not only increases the electrochemical surface area but also enhances the catalytic activity,thereby elevating the performance of alkaline HER.An investigation strategy combining experiments and calculations revealed the charge transfer law between multiple active components and the enhanced regulation mechanism of alkaline HER process,ultimately achieving a nearly twice increase in reaction overpotential of the as-fabricated catalyst at-10 mA·cm^(-2).This new approach provides a potential strategy for improving the efficiency of core catalyst for energy conversion technologies.

Effect of manganese doping on the thermoelectric properties of Zintl phase EuCd_2Sb_2

Polycrystalline samples of Zintl phase EuCd2-xMnxSb2 （0.05≤x≤0.6） with the CaAl2Si2-type crystal structure （space group P3ml） were synthesized via a solid-state reaction followed by suitable cooling, annealing and spark plasma sintering （SPS） processes. In samples with x=0.0, 0.1, 0.2, 0.4 and 0.6, the electrical conductivity, Seebeck coefficient, and thermal conductivity were performed as a function of temperature from 300 to 650 K. It was found that chemical substitution of Mn failed to optimize the thermoelectric properties of p-type conductive EuCd2Sb2. It was because that the Mn substitution induced the minority carriers （electrons）, resulting in decreasing the electrical conductivity drastically despite the fact that it enlarged the Seebeck coefficient and reduced the thermal conductivity synchronously.

Recent Progresses of UV Nonlinear Optical Materials

Ultraviolet(UV)nonlinear optical(NLO)crystal materials are hailed as the"chip"of the optoelectronic industry for they play a unique and crucial role in many newly developed scientific and technological applications.At present,due to the relatively single frequency doubling gene types of traditional NLO materials,the service performance of UV NLO materials is fundamentally restricted.Therefore,there is an urgent need to develop new synthesis methods,search for novel functional groups,expand new UV NLO materials systems,screen new high-performance crystals,and then break through performance bottlenecks.Herein,we review the recent progresses on UV NLO crystal materials.Furthermore,we prospect that these recently developed approaches will continuously extend their advantages in developing superior UV NLO materials in the near future.