Calcium titanate corrosion inhibitor enabling carbon as inert anode for oxygen evolution in molten chlorides

The corrosion inhibition efficacy of titanate(CaTiO_(3))for carbon anodes in molten salts was investigated through various analytical techniques,including linear sweep voltammetry,X-ray diffraction,scanning electron microscopy,and energy dispersion spectroscopy.The results demonstrate that the addition of CaTiO_(3)corrosion inhibitor efficiently passivates the carbon anode and leads to the formation of a dense CaTiO_(3)layer during the electrolysis process in molten CaCl_(2)-CaO.Subsequently,the passivated carbon anode effectively undergoes the oxygen evolution reaction,with an optimal current density for passivation identified at 400 m A/cm~2.Comprehensive investigations,including CaTiO_(3)solubility tests in molten CaCl_(2)-CaO and numerical modeling of the stability of complex ionic structures,provide compelling evidence supporting“complexation-precipitation”passivation mechanism.This mechanism involves the initial formation of a complex containing TiO_(2)·nCaO by CaTiO_(3)and CaO,which subsequently decomposes to yield CaTiO_(3),firmly coating the surface of the carbon anode.In practical applications,the integration of CaTiO_(3)corrosion inhibitor with the carbon anode leads to the successful preparation of the FeCoNiCrMn high-entropy alloy without carbon contamination in the molten CaCl_(2)-Ca O.

Electrochemical preparation of the Fe-Ni36 Invar alloy from a mixed oxides precursor in molten carbonates

The Fe-Ni36 alloy was prepared via the one-step electrolysis of a mixed oxides precursor in a molten Na2CO3-K2CO3 eutectic melt at 750℃,where porous Fe_(2)O_(3)-NiO pellets served as the cathode and the Ni10 Cu11 Fe alloy was an inert anode.During the electrolysis,Ni O was preferentially electro-reduced to Ni,then Fe_(2)O_(3)was reduced and simultaneously alloyed with nickel to form the Fe-Ni36 alloy.Different cell voltages were applied to optimize the electrolytic conditions,and a relatively low energy consumption of 2.48 k W·h·kg^(-1) for production of Fe Ni36 alloy was achieved under 1.9 V with a high current efficiency of 94.6%.The particle size of the alloy was found to be much smaller than that of the individual metal.This process provides a low-carbon technology for preparing the Fe-Ni36 alloy via molten carbonates electrolysis.

Electrochemical derusting in molten Na_(2)CO_(3)–K_(2)CO_(3)

The formation of a rust layer on iron and steels surfaces accelerates their degradation and eventually causes material failure.In addition to fabricating a protective layer or using a sacrificial anode, repairing or removing the rust layer is another way to reduce the corrosion rate and extend the lifespans of iron and steels.Herein, an electrochemical healing approach was employed to repair the rust layer in molten Na_(2)CO_(3)-K_(2)CO_(3).The rusty layers on iron rods and screws were electrochemically converted to iron in only several minutes and a metallic luster appeared.Scanning electron microscopy(SEM) and energy dispersive X-ray spectroscopy(EDS) analyses showed that the structures of the rust layer after healing were slightly porous and the oxygen content reached a very low level.Thus, high-temperature molten-salt electrolysis may be an effective way to metalize iron rust of various shapes and structures in a short time, and could be used in the repair of cultural relics and even preparing a three-dimensional porous structures for other applications.

Electrochemically recycling degraded superalloy and valorizing CO_(2)in the aff ordable borate-modified molten electrolyte

Integrating electrochemical reduction of CO_(2)and electrochemical oxidation to recycle degraded superalloys is a promising solution to ease resource scarcity and safeguard environmental sustainability.Herein,we propose an electrochemical technique for the conversion of bulk superalloy scraps and CO_(2)into oxide powder at the anode and solid carbon at the cathode,respectively.In particular,a borax-modifi ed CaCl_(2)-based molten salt electrolyte is used for enhancing the electrochemical oxidation of superalloy scraps.At a temperature of 700℃and a voltage of 2.8 V,90.55 wt.%of alloy scraps were oxidized in a molten CaCl_(2)–NaCl–CaCO_(3)–Na_(2)B_(4)O_(7)with an acid–base ratio(K_(a/b))of 1.The synergy of Cl−and B_(4)O_(7)2−of electrolyte prevents the passivation of the alloy anode and enables continuous oxidation.Furthermore,the Ni and Co in the anode products are recovered by sulfation roasting with recovery efficiencies of 85.58%and 95.27%for Ni and Co,respectively.Overall,modulating the alkalinity of the electrolyte for enhancing oxidation/pulverization of alloy scrap anode provides new insight into electrochemically recovering superalloy scraps.

Electrochemically exfoliated WS_(2)in molten salt for sodium-ion battery anode

The poor crystallinity and unstable crystal structure of tungsten disulfide(WS2)limit its application in practice.In this paper,a molten salt electrolysis method is proposed to intercalate metal ions into the interlayers of layered WS2 to obtain few-layer sheetlike structures.The effect of the molten salt system,applied constant current and electrolysis duration on the exfoliation degree of WS2 bulk has been investigated.The results show that the products electrolyzed in molten LiCl-NaCl-KCl and NaClKCl salts under 25 mA were more transparent and thinner flakes sheets due to the uniform intercalation of Li^+and Na^+with smaller size.The exfoliated WS_(2)was used as an anode material for sodium-ion batteries with a potential of 0.01-2.50 V.In comparison,the WS_(2)-NaCl-25 mA electrode displays a high reversible capacity of 373 mAh·g^(-1)at0.1 A·g^(-1)after cycling for 100 cycles at the same time showing great rate and cycle performance.It also presents a high capacitive ratio of 90.65%at 1.0 mV·s^(-1).The molten salt electrolysis provides a new perspective on the exfoliation of layered material,while demonstrating the great potential of WS2 as an anode material for sodium-ion battery.

Nickel leaching from low-grade nickel matte using aqueous ferric chloride solution

Nickel leaching from low-grade nickel matte(LGNM) using aqueous ferric chloride solution was studied.The influence of factors such as leaching temperature and concentration of ferric chloride on the nickel leaching ratio was investigated.The results show that increasing leaching temperature and concentration of ferric chloride increases the nickel leaching ratio.The overall nickel leaching process follows the unreacted shrinking core model,and the surface chemical reaction is the rate-controlling step.The activation energy and the reaction order of the nickel leaching process,controlled by the surface chemical reaction,were calculated to be 52.96 kJ mol^(-1)and 0.5,respectively.Therefore,the kinetics equation for the nickel leaching was found to be 1-(1-α)^(1/3)=7.18×10~4C^(0.5)exp[-52,960/(RT)]t.

Electrolytic alloy-type anodes for metal-ion batteries

Alloy-type metals/alloys hold the promise of increasing the energy density of metal-ion batteries(MIBs)because of their theoretical high gravimetrical capacities.Semimetals and semimetal-analogs are typical alloy-type anodes.Currently,the large-scale extraction of semimetals(Si,Ge)and semimetal-analogs(Sb,Bi,Sn)by traditional metallurgical routes highly relies on using reducing agents(e.g.,carbon,hydrogen,reactive metals),which consumes a large number of fossil fuels and produces greenhouse gas emissions.In addition,the common metallurgical methods for extracting semimetals involve relatively high operating temperatures and therefore produce bulk metal ingots solidified from the liquid metals.However,the commonly used electrode materials in batteries are fine powders.Thus,directly producing semimetal powders would be more energy efficient.In addition,semimetals are good candidates to host alkali/alkaline-earth ions through the alloying process because the electronegativity of semimetals is high.Therefore,preparing semimetal powders via an environment-sound manner is of great interest to provide sustainable anode materials for MIBs while reducing the ecological footprint.Low-cost and high-output capacity anode powder materials,as well as straightforward and environmental-benign synthetic methods,play key roles in enabling the energy conversion and storage technologies for real applications of MIBs.Electrochemical technologies offer new strategies to extract semimetals using electrons as the reducing agent that comes from renewable energies.Besides,the morphologies and structures of the electrolytic products can be rationally tailored by tuning the electrode potentials,electrolytes,and operating temperatures.In this regard,using the one-step green electrochemical method to prepare high-capacity and cheaper alloy-type metalloids for MIB anodes can fulfill the requirements for developing MIBs.This review critically overviews recent developments and advances in the electrochemical extraction of semimetals(Si,Ge)and semimetal-analogs(Sb,Bi,Sn)for MIBs,including basic electrochemical principles,thermodynamic analysis,manufacture strategies and applications in lithium-ion batteries(LIBs),sodium-ion batteries(SIBs),potassium-ion batteries(PIBs),magnesium-ion batteries(Mg-ion batteries),and liquid metal batteries(LMBs).It also presents challenges and prospects of employing electrochemical approaches for preparing alloy-type anode materials directly from inexpensive ore-originated feedstocks.