In-situ building of multiscale porous NiFeZn/NiZn-Ni heterojunction for superior overall water splitting

The development of efficient nonprecious bifunctional electrocatalysts for water electrolysis is crucial to enhance the sluggish kinetics of the oxygen evolution reaction(OER)and hydrogen evolution reaction(HER).A self-supporting,multiscale porous NiFeZn/NiZn-Ni catalyst with a triple interface heterojunction on nickel foam(NF)(NiFeZn/NiZn-Ni/NF)was in-situ fabricated using an electroplating-annealing-etching strategy.The unique multiinterface engineering and three-dimensional porous scaffold significantly modify the mass transport and electron interaction,resulting in superior bifunctional electrocatalytic performance for water splitting.The NiFeZn/NiZn-Ni/NF catalyst demonstrates low overpotentials of 187 m V for HER and 320 mV for OER at a current density of 600 mA/cm^(2),along with high durability over 150 h in alkaline solution.Furthermore,an electrolytic cell assembled with NiFeZn/NiZn-Ni/NF as both the cathode and anode achieves the current densities of 600 and 1000 m A/cm^(2) at cell voltages of 1.796 and 1.901 V,respectively,maintaining the high stability at 50 mA/cm^(2) for over 100 h.These findings highlight the potential of NiFeZn/NiZn-Ni/NF as a cost-effective and highly efficient bifunctional electrocatalyst for overall water splitting.

多界面耦合空心核壳MnCoSe_(x)/MnO@氮掺杂碳复合材料的制备及电化学性能

通过简单的溶剂热和硒化策略以及进一步的碳层包覆程序制备氮掺杂碳壳包裹的空心MnCoSe_(x)/MnO纳米球(MnCoSe_(x)/MnO@N-C)。得益于MnCoSe_(x)和MnO之间的多界面耦合以及独特的空心核壳结构,MnCoSe_(x)/MnO@N-C复合材料具有较高的比电容和优异的倍率性能,即使在5 A/g的高电流密度下,MnCoSe_(x)/MnO@N-C仍可以稳定运行20000次循环,并保持84.6%的初始比电容。由MnCoSe_(x)/MnO@N-C和活性炭组装的非对称超级电容器器件在功率密度为810 W/kg时表现出11.2 W·h/kg的高能量密度,并拥有超长的循环寿命,在20000次循环后仍可保留初始比电容的84.0%。

One-step construction of strongly coupled Co_(3)V_(2)O_(8)/Co_(3)O_(4)/MXene heterostructure via in-situ Co-F bonds for high performance all-solid-state asymmetric supercapacitors

Co_(3)V_(2)O_(8)/Co_(3)O_(4)/Ti_(3)C_(2)T_(x) composite was easily synthesized via one-step succinct-operated hydrothermal process.The interconnected Co_(3)V_(2)O_(8)/Co_(3)O_(4) nanowires network can in-situ grow and anchor on the surface of Ti_(3)C_(2)T_(x) via the strong Co-F bonds and contribute tremendously to depress Ti_(3)C_(2)T_(x) self-restacking.Profiting from the synergistically interplayed effect among the multiple interfaces and high conductivity of Ti_(3)C_(2)T_(x) as well as outstanding stability of the as-designed nanostructure,the optimum Co_(3)V_(2)O_(8)/Co_(3)O_(4)/Ti_(3)C_(2)T_(x)electrode reaches a commendable specific capacitance(up to 3800 mF·cm^(−2)),great rate capability(80%capacitance retention after 20-times current increasing),and preeminent cycling stability(95.4%/85.5%retention at 7000th/20,000th cycle).Moreover,the all-solid-state asymmetric supercapacitor based on Co_(3)V_(2)O_(8)/Co_(3)O_(4)/Ti_(3)C_(2)T_(x) and active carbon can deliver a high energy density of 84.0μWh·cm^(−2) at the power energy of 3.2 mW·cm^(−2),and excellent cycling durability with 87.0%of initial capacitance retention upon 20,000 loops.This work provides a practicable pathway to tailor MXene-based composites for high-performance supercapacitor.

Enhancing zinc storage performance of Mn_(3)O_(4)cathode through Ag-doping and-crosslinking dual-modification strategy

Octahedral Mn_(3)O_(4)nanoparticles with an Ag-doping and nanoporous Ag(NPS)framework was simply fabricated through an alloying-etching engineering.The dual-modified Mn_(3)O_(4)(denoted as Ag−Mn_(3)O_(4)/NPS)consists of Ag-doped Mn_(3)O_(4)nanoparticles crosslinked with three dimensional nanoporous Ag framework.The incorporated Ag dopant is effective in improving the intrinsic ionic and electronic conductivities of Mn_(3)O_(4),while the NPS framework is introduced to improve the electron/mass transfer across the entire electrode.Profiting from the dual-modification strategy,the Ag−Mn_(3)O_(4)/NPS exhibits admirable rate capability and cycling stability.A high reversible capacity of 88.7 mA·h/g can still be retained for over 1000 cycles at a current density of 1 A/g.Moreover,a series of ex-situ experimental techniques indicate that for Ag−Mn_(3)O_(4)/NPS electrode during the zinc ion storage,Mn_(3)O_(4)is electrochemically oxidized into various MnOx(e.g.,Mn_(2)O_(3),MnO2)species in the initial charging,and the subsequent battery reaction is actually the intercalation/deintercalation of H+and Zn2+into MnOx.

Carbon shell coated hollow NiCoSe_(x)composite as high-performance anode for lithium storage

Hollow NiCoSe_(x)(H-NiCoSe_(x)) nanospheres encapsulated with carbon shell were prepared via one-step easy solvothermal method followed by the carbon coating process.H-NiCoSe_(x)@C has large interior void with the uniform dimension around 350 nm and the thickness of carbon shell around 20-30 nm.Coupling with the large interior void as well as robust protective carbon shell,H-NiCoSe_(x)@C can retain the reversible capacity of 805.6 mAh·g^(-1) after 100 cycles at 200 mA·g^(-1).In particular,H-NiCoSe_(x)@C delivers large reversible capacity of 1532.2 mAh·g^(-1) upon cycling for 1000 loops at 1000 mA·g^(-1)with the capacity retention as high as 128.2% upon long period of activation.Even at the high rate of 3000 mA·g^(-1),its specific capacity still retains up to 659.3 mAh·g^(-1).The superior lithium storage performances for H-NiCoSe_(x)@C profit from its robust hollow core-shell structure as well as enhanced electrical conductivity and ion transport.

Catalyst-free hydrochlorination protocol for terminal arylalkynes with hydrogen chloride

We present a simple and straightforward protocol for hydrochlorination of terminal arylalkynes to vinyl chlorides using hydrogen chloride under mild reaction conditions. This protocol does not involve any metal catalysts or additives. It is simple, inexpensive, and easy to prepare, and exhibits good reaction activity. The hydrochlorination proceeds smoothly to yield unique regioselective products via the Markovnikov addition rule.