Two-dimensional materials based on ternary system of B, C and N are useful ranging from electric devices to catalysis. The bonding arrangement within these BCN nanosheets largely determines their electronic structure and thus chemical and (or) physical properties, yet it remains a challenge to manipulate their bond structures in a convenient and controlled manner. Recently, we developed a synthetic protocol for the synthesis of crumpled BCN nanosheets with tunable B and N bond structure using urea, boric acid and polyethylene glycol (PEG) as precursors. By carefully selecting the synthesis condition, we can tune the structure of BCN sheets from s-BCN with B and N bond together to h-BCN with B and N homogenously dispersed in BCN sheets. Detailed experiments suggest that the final bond structure of B and N in graphene depends on the preferentially doped N structure in BCN nanosheets. When N substituted the in-plane carbon atom with all its electrons configured into the π electron system of graphene, it facilitates the formation of h-BCN with B and N in separated state. On the contrary, when nitrogen substituted the edge-plane carbon with the nitrogen dopant surrounded with the lone electron pairs, it benefits for the formation of B-N structure. Specially, the compound riched with h-BCN shows excellent ORR performance in alkaline solution due to the synergistic effect between B and N, while s-BCN dominant BCN shows graphite-like activity for ORR, suggesting the intrinsic properties differences of BCN nanosheets with different dopants bond arrangement.

Nitrogen-doped graphene sheets (NGS), synthesized by annealing graphite oxide (GO) with urea at 700-1050 °C, were studied as positive electrodes in a vanadium redox flow battery. The NGS, in particular annealed at 900 °C, exhibited excellent catalytic performance in terms of electron transfer (ET) resistance (4.74 ± 0.51 and 7.27 ± 0.42 Ω for the anodic process and cathodic process, respectively) and reversibility (ΔE = 100 mV, Ipa/Ipc = 1.38 at a scan rate of 50 mV s(-1)). Detailed research confirms that not the nitrogen doping level but the nitrogen type in the graphene sheets determines the catalytic activity. Among four types of nitrogen species doped into the graphene lattice including pyridinic-N, pyrrolic-N, quaternary nitrogen, and oxidic-N, quaternary nitrogen is verified as a catalytic active center for the [VO](2+)/[VO2](+) couple reaction. A mechanism is proposed to explain the electrocatalytic performance of NGS for the [VO](2+)/[VO2](+) couple reaction. The possible formation of a N-V transitional bonding state, which facilitates the ET between the outer electrode and reactant ions, is a key step for its high catalytic activity.

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Employing the principle of isostructural alloying, a series of unprecedentedly wide Curie-temperature windows (CTWs), covering the ultimate temperature range of first-order magnetostructural phase transitions (MSTs), are realized between 40 and 450 K for the strongly-coupled MSTs in a single host system Mn 1-y Fe y NiGe 1-x Si x . Throughout the wide CTWs, the highly tunable MSTs show large magnetization jump, low-field effects, high-temperature giant magnetocaloric effects and robust functional stability, providing important properties to phase-transition-based magneto-multifunctional applications, including field-driven shape memory, magnetic cooling/heating and energy conversion. The unprecedentedly wide CTWs open up a design platform for magneto-multifunctional multiferroic alloys that can be manipulated in a quite large temperature space in various scales and patterns, and by multiple physical fields. Keywords:Curie-temperature window, magnetic shape memory alloy, magnetocaloric effect, ferromagnetic martensitic transition, magnetostructural transition 3 A coupling of ferroelasticity and ferromagnetism [1, 2] can lead to a multiferroic behavior of first-order magnetostructural phase transition (MST) in magnetoelastic materials.Attractive physical effects, such as ferromagnetic shape memory, [3] magneto-strain, [4] magnetocaloric effect (MCE), [5, 6] magnetoresistance, [7] and exchange bias, [8] are observed based on the MSTs. These effects are receiving increasing attentions from the applications in actuating, [9] sensing, [10] magnetic cooling, [11] heat pump [12] and energy conversion. [13] As an important class of MSTs, ferromagnetic martensitic transformations (FMMTs) are widely found in Heusler, Fe-based, and MM'X alloys, and produce diversiform physical discontinuities due to the significant alterations in crystallographic, electronic, orbital and magnetic structures in the systems. Extraordinary magneto-multifunctional properties emerge thereby and can be tuned in different ways.Profiting from FMMTs, the magnetic-field-induced shape memory effect and giant magneto-strain/magnetostriction have been extensively studied with promising potential in micro-mechanical controls and strain outputs. The magnetocaloric effect (MCE), [14] which happens in a magnetic transition, can be enhanced appreciably by first-order FMMTs with great changes in structural entropy in spin-lattice coupled systems. [15][16][17] Materials bearingFMMTs are thus further considered as candidates for caloric applications, probably combined with mechanocaloric or electrocaloric effects. [18, 19] Very recently, an inspiring application of electric power generation, [20, 21] using first-order FMMT ferromagnets driven by high-temperature heat resources, becomes increasingly attractive for the energy conversion, which demonstrates an exciting advance in magneto-multifunctionalities of magnetoelastic alloys. 4 For all the magneto-multifunctionalities, the magnetostructural coupling play...

High performance nanogenerators (NGs) are critically important for energy harvesting and powering micro/nano-devices. Environmentally friendly nanowires (NWs) with high piezoelectric coefficients are highly desirable for enhancing NGs' performance and expanding their applications. In this paper, we synthesized a new kind of lead-free 0.5Ba(Zr 0.2 Ti 0.8 )O 3 -0.5(Ba 0.7 Ca 0.3 )TiO 3 (BZT-BCT) NWs with high piezoelectric coefficients through the electrospinning method and subsequent calcining process. Their crystal structure and formation mechanism were systematically studied. Furthermore, BZT-BCT NWs were made into a high performance flexible NG. It could harvest weak mechanical movement energy and generate an output voltage of 3.25 V and output current of 55 nA, which is large enough to directly power a commercial liquid crystal display (LCD).

Materials with high carrier mobility showing large magnetoresistance (MR) have recently received much attention because of potential applications in future high-performance magnetoelectric devices. Here, we report on an electron-hole-compensated half-Heusler semimetal LuPtBi that exhibits an extremely high electron mobility of up to 79 000 cm 2 /V s with a nonsaturating positive MR as large as 3200% at 2 K. Remarkably, the mobility at 300 K is found to exceed 10 500 cm 2 /V s, which is among the highest values reported in three-dimensional bulk materials thus far. The clean Shubnikov-de Haas quantum oscillation observed at low temperatures and the first-principles calculations together indicate that the high electron mobility is due to a rather small effective carrier mass caused by the distinctive band structure of the crystal. Our findings provide a different approach for finding large, high-mobility MR materials by designing an appropriate Fermi surface topology starting from simple electron-hole-compensated semimetals.

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