Electrochemical Preparation And Catalytic Performance Of Multifunctional Nanoporous Copper Membrane In Eutectic Solvent

Nanoporous copper(NPC)with three-dimensional network structure exhibit large surface-to-volume ratios,relatively low density and excellent electrical conductivity that have attracted great interest for various applications,such as catalysis,fuel cells,chemical sensors,etc.Up to now,template method and dealloying method are the most widely use strategy to fabricate NPC,impressively,electrochemical dealloying offers a relatively versatile route for the preparation of various nanoporous metals.Nevertheless,the electrochemical fabrication of nanoporous metals in most previous reported work involves hazardous acidic or alkaline reagent,which is highly corrosive and environmentally unsustainable.Deep eutectic solvents a new environmental friendly solvent have drawn enormous attention as alternative media for the for many technological application because of their distinct advantages,such as a wide electrochemical window,high ionic conductivity,extremely low vapor pressures,nontoxic,biodegradable and thermal stability.Herein,we conceive of using DESs as potential alterative media to solve the problems existing in previous reported dealloying nanoporous copper methods.Subsequently,using NPC as the skeleton template to be immersed in the deep eutectic solvent containing nickel salt precursor to fabricate core-shell composite nanoporous electrode by replacement reaction,then to explore their catalytic properties.The main research work is as follows:(1)NPC was fabricated from the ZnO/reline,Zinc component in the electrochemically formed Cu-Zn surface alloys can be further selectively removed to create nanoporous copper at the potential of-0.4 V vs Ag.As indicated by CV and XRD results,this Cu-Zn surface alloy phases transformation/dealloying process exhibits highly temperature dependence.The selective dissolution procedure opens up a percolating path throughout the whole alloy layer to fabricate 3D structure with a thickness of several hundred nanometers(ca.200 nm).Dealloying temperature plays an essential role in controlling the surface diffusivity of the copper atoms during the dealloying process.In order to fabricate a 3D,open and bicontinuous nanoporous copper in this ChCl-Urea eutectic melt,a dealloying temperature of 393 K is necessary(2)3D hierarchical NPC films with controlled channels/pores size distribution can be synthesized by in-situ electrochemical strategy from ZnCl2/ethaline.The surface phase transformation on the copper substrate by galvanostatic electrodeposition at 373 K involves the formation of CuZn5,CU4Zn,and Cu5Zn8 alloys.A following in-situ selectively etching of active zinc element from those electrochemically formed multi Cu-Zn alloys leads to the generation of NPC with hierarchical architectures.Because of low viscosity and fast mass transfer in ethaline,The fast selective dissolution of zinc atoms triggers a development of large-sized channels/pores on the top surface,and the slow interface diffusion/self-assembly of Cu atoms dominates the dynamical porosity evolution of bicontinuous nanoporous structures.A higher dealloying temperature can significantly enhance the dealloying process and accelerate the evolution of nanoporous structures.The length scales of channels/pores,thickness as well as surface-to volume ratio of NPC can be tailored via altering dealloying temperature for an appropriate duration.The NPC prepared at optimal conditions gives a sensitivity up to 3415 ?A mM-1 cm-2 with a detection limit of 1.92 ?M,which is a promising electrode material for high-performance nitrate sensors.(3)3D interconnected core/shell nanoporous nickel(Ni@NPC)can be fabricated by simple galvanic replacement in NiCl2·6H2O/ChCl-EG solvent at a temperature of 353 K with a NPC template as the sacrificial template.The as-fabricated Ni@NPC exhibits high HER catalytic activity with a low overpotential of 170 mV for 10 mA·cm-2 HER current density(?10),a large exchange current density(j0)of 0.186 mA·cm-2 and a relatively small Tafel slope(b)of 98.5 mV-dec'1,which is superior or comparable to those obtained for nanostructured nickel based HER catalysts in alkaline media.(4)3D hierarchically porous Ni3S2 films on a nanoporous copper substrate(Ni3S2@NPC)by unusual galvanic replacement reaction in the NiCl2·6H2O-CH4N2S/ethaline solvent under an open operating system.Ni3S2@NPC electrode is binder-free and exhibits good structural integrity with high conductivity.A mild evolution of bulk gas bubbles(H2-O2 gas mixture)is proved to drive an in-situ structure rearrangement process of the Ni3S2@NPC and results in substantial increases in the HER activity.The activated Ni3S2@NPC(a-Ni3S2@NPC)electrode can serve as a highly efficient and stable electrocatalyst for the HER in water over a wide pH range.Significantly,it displays high-performance HER catalytic activity in acidic media with robust durability over 111 h and functions well under alkaline and neutral conditions.