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The indoor low-concentration formaldehyde (HCHO) removal in cobalt-based catalysts is still a “hot potato”. In this work, metal–organic-frameworks (MOF)-derived and Zinc (Zn)-modulated new cobalt nanoparticles catalyst (CZ-Co@NC-800) was designed and prepared. The CZ-Co@NC-800 performed outstanding elimination activities for ~1 ppm HCHO at 25 °C. In the static test condition, it achieves complete HCHO removal in 3 h at a relative humidity (RH) of ~55%. Moreover, 90.18% HCHO removal ratio is held after five recycle tests. In the dynamic test condition, it remains the characteristic to eliminate around 95.89% of HCHO within 8 h under an RH of ~55% and a gas hourly space velocity (GHSV) of ~150,000 mL·h−1g−1. Such advanced results should be ascribed to large specific surface area bringing about more cobalt active sites; and it is also because residual Zn metal affects the electronic structure of CZ-Co@NC-800 and enhance the surface charge transfer rate, thus the activation and dissociation ability of oxygen is promoted. Besides, a short HCHO reaction path over CZ-Co@NC-800 which was clarified by the In situ DRIFTs is also a reason for excellent catalytic performance. This work represents a crucial addition to expand the family of cobalt-based catalysts for indoor HCHO elimination.

The development of high–efficiency and low–cost bifunctional oxygen electrocatalysts is critical to enlarge application of zinc–air batteries (ZABs). However, it still remains challenges due to their uncontrollable factor at atomic level during the catalysts preparation, which requires the precise regulation of active sites and structure engineering to accelerate the reaction kinetics for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, a novel Co–doped mixed lanthanum oxide and hydroxide heterostructure (termed as Co–LaMOH|OV@NC) was synthesized by pyrolysis of La–MOF–NH2 with spontaneous cobalt doping. Synergistic coupling of its hollow structure, doping effect and abundant oxygen vacancies creates more active sites and leads to higher electroconductivity, which contribute to the better performance. As employed as a bifunctional oxygen electrocatalyst, the resulting 3Co–LaMOH|OV@NC exhibits superior electrocatalytic activity for both ORR and OER. In assembled ZAB, it also demonstrates an excellent power density of 110.5 mW cm−2, high specific capacity of 810 mAh gZn−1, and good stability over 100 h than those of Pt/C + RuO2. Density functional theory (DFT) calculation reveals that the heterointerfaces coupled with oxygen vacancies lead to an enhanced charge state and electronic structure, which may optimize the conductivity, charge transfer, and the reaction process of catalysts. This study provides a new strategy for designing highly efficient bifunctional oxygen electrocatalysts based on rare earth oxide and hydroxides heterointerface.

Single atom catalysts (SACs) with unique structure gain much interest in the field of electrocatalysis and show a broad application prospect in long-life rechargeable Zn-air batteries. However, ingenious design and preparation of bi-metal SACs is still difficult to further enhance the bifunctional electrocatalytic activity. Herein, modified zeolitic imidazolate frameworks (SiO2@Fe-ZIF-8/67) was facilely designed to preparation atomically dispersed Fe and Co doping 3D nitrogen-doped carbon nanosheets (A-FeCo@NCNs). The Fe or Co single atoms are identified to be coordinated with N atoms and form FeN4, CoN4 or N3Fe-CoN3 anchored on 3D defect carbon, which act as reactive sites for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Through synergetic coupling effect, A-FeCo@NCNs exhibits excellent electrochemical performance with ORR/OER potential gap of 0.80 V. Density functional theory (DFT) calculations further indicate the synergistic effect between Fe and Co in A-FeCo@NCNs towards the enhancing ORR activity. The as-prepared catalyst assembled Zn-air battery shows a maximum power density, and superb cycling stability, surpassing that based on commercial Pt/C + IrO2. Results from this study may provide a facile method for precious control of dual-metal single sites doped carbon with highly activity and durability for bifunctional electrocatalysis.

This work proposes a strategy to synthesize N-doped defective carbon (NDC), followed by trapping the FePc precursor. After pyrolysis, the optimized Fe–N–NDC-1-900 exhibits robust anchoring ability to immobilize atomic Fe species with abundant Fe–N4 sites, demonstrating excellent electrocatalytic activity in both the oxygen reduction reaction (ORR, E1/2 = 0.89 V, Eonset = 1.06 V) and oxygen evolution reaction (OER, E10 = 1.58 V). It also shows outstanding stability and delivers faster kinetics in oxygen electrocatalysis. Furthermore, the bifunctional Fe–N–NDC-1-900 is fabricated for a Zn–air battery, which demonstrates a high open-circuit voltage of 1.479 V, power density of 266 mW cm−2, specific capacity of 786 mA h gZn−1, and excellent reversibility with long-term cycling. DFT suggests that the high ORR activity is mainly ascribed to its high electronegativity and small energy barriers, produced by the adjacent pore defects and optimal charge redistribution.

The oxygen reduction reaction (ORR) is identified as a core issue in the technologies for convert energy, especially in proton-exchange membrane fuel cell (PEMFC). Highly reactive, low-cost, and du...

A novel amphoteric membrane was designed by blending polyvinylpyrrolidone (PVP) with sulfonated poly(ether ether ketone) (SPEEK) to fabricate a vanadium redox flow battery. Acid–base pairs were formed by sulfonic acid and heterocyclic nitrogen, and the dense network structures were interwoven by the hydrogen bonds between the acid–base pairs. Vanadium ions were blocked by these network structures such that their penetration was weakened. Compared with Nafion115 and SPEEK membranes, the ion selectivity of SPEEK/PVP (S/P) hybrid membranes of various proportions was improved, of which the S/P-30% membrane performed best (106.1*104 S min cm−3). At the same time, these hybrid membranes showed far superior performances than the single-component membranes in a single-cell system. Most notably, the coulombic efficiency and energy efficiency achieved by the battery with a S/P-30% hybrid membrane were 97.5% and 84.5% at 60 mA cm−2, respectively, with notable stability after 50 cycles. The corresponding open-circuit voltage of the battery was maintained above 0.8 V for more than 73 h. This acid–base hybrid membrane has reached a high level of overall performance in binary non-fluorine proton exchange membranes in recent years.

Defect modulation usually has a great influence on the electronic structures and activities of photocatalysts. Here, atomically layered g-C3N4 modified via defect engineering with nitrogen vacancy ...

Ever-increasing energy needs together with environmental concerns have accelerated development of alternative energy solutions, including storage and conversion. One such solution is usage of super...

To obtain the electrocatalyst with an improved electrocatalytic performance towards formic acid electro-oxidation (FAEO), a simple impregnation method is used to prepare Pt3Ni nanoparticles loaded on carbon black, assisted with electrochemically dealloying process. The X-ray powder diffraction (XRD) results as well as transmission electron microscopy (TEM) analysis of as-synthesized electrocatalyst demonstrates that the reduction temperature has a great influence on the FAEO activity of the dealloyed Pt3Ni nanoparticles. X-ray photoelectron spectroscopy (XPS) analyses confirm the variation in the electronic structure of platinum by incorporation of nickel atoms which reduces chemisorption of toxic carbon monoxide and promotes the dehydrogenation pathway of FAEO. The size of the dealloyed Pt3Ni nanoparticles remains within the range of about 2.7 nm. All electrochemical results illustrate that the performance of the as-obtained electrocatalyst towards the FAEO is significantly enhanced. Moreover, the carbon black content, incorporation of Ni atoms, and reduction temperature conditions have been proven to be the key factors for modification of the crystal structure and morphology which leads to enhanced catalytic performance.

Oxygen vacancy plays an important role in catalytic oxidation of formaldehyde (HCHO), but the inherent drawback of its thermodynamic instability causes the deactivation of catalysts. Hence, improving the thermodynamic stability of oxygen vacancy is a crux during HCHO oxidation. Here, a novel and simple nitrogen doping of MnO2/C catalyst is designed for HCHO oxidation at room temperature. The surface lattice oxygen of MnO2 will be activated by nitrogen-doping, which acts as active sites for HCHO oxidation and solves the thermodynamic instability issue of oxygen vacancy. Furthermore, carbon is doped with nitrogen to promote electron transfer and accelerate the HCHO oxidation process. Therefore, the catalytic activity and stability of the catalyst can be significantly promoted, which can completely remove ∼1 ppm HCHO in the tank within 3 h, and remains highly active after 5 cycles at room temperature (RH = 55%). In addition, the excellent removal performance over the prepared catalyst is also attributed to abundant surface oxygen species, amorphous crystallinity, and low reduction temperature. In situ diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) and density functional theory (DFT) calculations reveal the reaction mechanism of HCHO. This strategy provides crucial enlightenment for designing novel Mn-based catalysts for application in the HCHO oxidation field.

Developing efficient and cost-effective oxygen reduction reaction (ORR) catalysts for fuel cells is quite necessary but still full of challenges. In this study, tungsten nitride nanosheets (WN NSs) decorated with nitrogen-containing carbon dots hybrid materials are developed using a facile two-step route. Specifically, a sandwich-like porous electrode, which contains a N-doped carbon layer encapsulated with uniform carbon dots (N-CDs) and a sheet-like WN for both-side formation of N-CDs, is obtained and designed as a novel type of ORR catalysts (denoted as N-CDs@WN). The N-CDs@WN hybrid shows superior catalytic activity via a four-electron pathway and demonstrates excellent stability over long periods of time and resistance to methanol. The excellent electrocatalytic properties of N-CDs@WN hybrids benefited from a hierarchical structure with large specific area, numerous active sites, and synergistic effect between CDs and WN that can facilitate the conductivity and mass transfer during the ORR process. Compared to other carbon dots-based nanocomposites, our facile synthetic route for N-CDs@WN not only presents the advantages of being relatively green, simple, and cost-effective but also is an attractive alternative for the electrocatalyst in the non-precious ORR.

Titanium nitride hollow spheres (TiN HSs) consisting of TiN nanosheets have been developed with a carbon-template-assisted strategy. The residual carbon is activated during the removal of the carbo...

This work proposes an extraction process for thorough removal of various impurities in crude bismuth. In the process, crude bismuth was pickled with nitric acid, and then the bismuth in the filtrate was extracted into the organic phase by TBP. After scrubbing with a saturated NaNO3 solution, stripping was carried out by NaOH solution, and a rod-shaped α-Bi2O3 precipitate was obtained. Increasing the concentration of NO3− and TBP and the ratio of Vo/Va could greatly increase the extraction efficiency of bismuth or the separation factor of impurities. Bismuth is extracted in the form of Bi(NO3)3·TBP, and the results of quantum chemical calculations indicated that both intermolecular forces and chemical bonds exist between the Bi(NO3)3 and TBP molecules. Thermodynamic analysis based on the Debye-Huckel equation under large ionic strength conditions showed that the extraction reaction is exothermic and proceeds spontaneously. Under the optimized extraction conditions, the extraction efficiency, elution efficiency, and stripping efficiency of bismuth were 98.5%, 0.55%, and 96.2%, respectively. All of the impurity elements were thoroughly removed after extraction. In particular, the separation factor βBi/M of M = Te, As, Cu, and Sb, which are prone to codeposition with bismuth during electrodeposition, were 160, 183, 982, and 359, respectively. The purity of α-Bi2O3 obtained by this method was as high as 99.95%

The purification of tellurium (Te) has received considerable attention as the cadmium telluride (CdTe) photovoltaic modules have become one of the lowest-cost products of solar electricity. An optimum tellurium (Te) purification process consists impurity separation, electrodeposition, and ultrasonic cleaning was proposed first time for preparing 99.99% (4N) purity of Te from alkaline leaching solution which contains high level impurities. The main metallic impurities copper (Cu), lead (Pb), iron (Fe), and bismuth (Bi) were effectively separated from the solution by adding appropriate quantity of sodium sulfide nonahydrate (Na2S·9H2O) before electrodeposition. The impurities arsenic (As) and selenium (Se) were further removed by ultrasonic cleaning. Under the optimum process, 4N-Te powder was prepared, meanwhile, the impurity contents of Cu, Se, As, Pb, Fe, Bi, magnesium (Mg), and sulfur (S) in the Te product all met the 4N-Te standard, along with the impurity contents of As and Se in the Te product were lower than 2 ppm after ultrasonic cleaning. The chemical composition of the Te product was identified by inductively coupled plasma optical emission spectrometer (ICP-OES). Furthermore, the electrochemical behavior of Te on the titanium (Ti) plate in the alkaline leaching solution was studied by linear sweep voltammogram (LSV), electrochemical impedance spectroscopy (EIS) and chronopotentiometry (CP). The morphology, structure and purity of Te product were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-rays (EDX). 4N-Te product with hexagonal single crystal structure was obtained by the optimum Te purification process based on electrodeposition method.

Aiming to further promote the performance of PdNi for formic acid electro-oxidation (FAEO), ternary Pd-Ni-Ir/C nanocatalyst was synthesized via an ethylene glycol-assisted NaBH4 reduction process. The physical characterizations show that the PdNiIr nanoparticles with a small mean size are well dispersed on carbon support. The electrochemical measurements demonstrate that the PdNiIr/C catalyst exhibits the highest activity for FAEO. The onset and peak potential of FAEO on PdNiIr/C is about 70 mV more negative than that on the Pd/C and PdNi/C catalysts. The mass activity of Pd in PdNiIr/C at 0.14 V is 2830 mA mg−1Pd, which is about 1.65, 1.82, and 2.2 times as high as that of PdIr/C, PdNi/C, and Pd/C, respectively. The enhancement should be attributed to the electronic effect and bi-functional mechanism.

Aluminum-air batteries (AABs) are deemed as a potential clean energy storage device. However, exploiting high-efficiency and stable oxygen reduction reaction (ORR) electrocatalysts in AABs is still a challenge. Iron phthalocyanine (FePc) shows a great prospect in ORR but still far from Pt-based catalysts. Here, the hybrid electrocatalysts of monolayer FePc and hollow N,S-doped carbon spheres (HNSCs) are innovatively constructed through π-π stacking to achieve high dispersion. The resulting FePc@HNSC catalyst exhibits an outstanding ORR activity, outperforming that of pristine FePc and even most Fe-based catalysts reported to date. Moreover, the AAB using FePc@HNSC catalyst not only demonstrates a superior power density than the battery with Pt/C, but also displays stable discharge voltages and excellent durability. Furthermore, the theoretical calculations confirm that the charge distribution and d-band center of the Fe atom in FePc are efficiently optimized by hybrid configuration via the introduction of N,S-doped carbon substrate. The design leads to an enriched electron density around Fe active sites and significant reduction of energy barrier for OH* formation, which are favorable for the improvement of electrocatalytic ORR performance. This work provides a chance to expand the application of metallic macrocyclic compound electrocatalysts in various energy technologies.

A novel fluorinated acid-base sulfonated polyimide membrane (s-f-SPI) with trifluoromethyl (-CF3), side-chain-type-SO3H and benzimidazole groups was synthesized by a 2-step method for vanadium redox flow battery applications. A series of physico-chemical properties of s-f-SPI membrane were researched systematacially. The acid-base pairs between the side-chain-type -SO3H and protonated imidazole groups provided more channels for proton-transport, enhancing the proton conductivity (0.51×10−1 S cm−1 at ∼25 °C), and Donnan effect of the imidazole groups impeded the penetration of vanadium-ion (3.95×10−7 cm2 min−1). In VRFB tests, s-f-SPI membrane exhibited a coulombic efficiency (CE) of 98.1% and an energy efficiency (EE) of 81.2% at a current density of 100 mA cm−2, higher than those of Nafion 212 (CE: 94.1%, EE: 76.5%). Furthermore, the VRFB with s-f-SPI membrane showed a stable performance in the 500 cycles charging-discharging test at 100 mA cm−2, and the morphology and structure remained unchanged after the cycle test. These results demonstrate that the s-f-SPI membrane has great potential for VRFB applications.

The low-concentration HCHO removal at room temperature is still a challenge in the indoor air purifying. Manganese dioxide catalyst (MnO2-M) derived from metal-organic frameworks (MOF) was synthesized via facile in-situ redox reaction. The obtained MnO2-M catalyst displayed superior activity and stability for low-concentration HCHO removal, reaching ~95% for 1.0 mg/m3 of HCHO under dynamic test mode and degrading 93.1% for 1.0 mg/m3 HCHO in 3 h under static test mode at room temperature. Moreover, the enhanced activity of MnO2-M could be attributed to the abundant chemisorbed oxygen species, numerous Mn-vacancies and proper pore size distribution. More crucially, the chemisorbed oxygen species on the MnO2-M could be rapidly activated by the transferable electrons and vacancies, thus significantly promoting the formation of reactive oxygen species and HCHO decomposition. The present work provides a new strategy to develop efficient catalyst for indoor air purification.

The nano-on-micro heterostructure photocatalyst BiOI-MoS2/CdS was synthesized through facile in-situ hydrothermal and solvothermal growth methods. The heterostructures formed between BiOI, MoS2 and CdS realized a step-wise electron transfer process, thus reducing the charge recombination effectively. The light absorption range of the composite was expanded with the incorporation of BiOI. The specimen acts out a state-of-the-art hydrogen evolution of 14000 μmol/g/h under visible light (λ > 420 nm), which was far exceeding MoS2/CdS (460 μmol/g/h) by a factor of 30. BiOI is firstly applied to promote photocatalytic water splitting into hydrogen. What's more, the cost of photocatalytic water splitting into hydrogen will be greatly reduced by replacing noble metal cocatalyst with MoS2. The opportunities for developing low-cost efficient photocatalysts for water splitting may be opened because of this discovery.

A new catalysts electrode was prepared by in situ controllable deposition of Pd shell layer on the gas diffusion layer (GDL) supported Ni(OH) 2 nanoparticles using atomic layer deposition (ALD) technology. High resolution transmission electron microscope confirmed that the Ni(OH) 2 core was coated by several atomic layers of Pd. The core-shell Ni(OH) 2 @Pd catalysts with different thickness of Pd shell are easily prepared by controlling ALD cycle. Electrochemical tests showed that the 100-Ni(OH) 2 @Pd/GDL catalyst prepared via 100 ALD cycles presented the highest catalytic activity for ethanol electro-oxidation reaction (EOR). The peaking current density of Ni(OH) 2 @Pd/GDL was 1439 mA mg Pd −1 , which was about 2.75 times as high as that of Pd/GDL (522 mA mg Pd −1 ). The shift in binding energy of the XPS peak of Pd in Ni(OH) 2 @Pd catalyst confirmed the strong interaction between the Pd shell and the Ni(OH) 2 core. We suggested that the high catalytic activity of Ni(OH) 2 @Pd/GDL catalyst layer may be due to following factors: high Pd dispersion arising from the core-shell structure, high Pd utilization because of the in situ deposition of Pd on catalyst layer and the interaction between the Pd shell and the Ni(OH) 2 core. Herein, the ALD technology exhibits a promising application prospect for preparing core-shell structure and precisely controlling shell thickness of nano-composite as an electro-catalyst toward EOR.

Intermetallic nanoparticles are one of promising electrocatalysts in fuel cells for controllable component and structure. Herein we discussed the optimal annealing temperature for synthesis of platinum-tellurium catalysts with combination of dealloying process. Compared with previous work about PtTe intermetallic nanoparticles, as-prepared dealloyed nanoparticles showed superior performance by tuning formic acid oxidation to occur through dehydrogenation pathway after electrochemical dealloying process. The dealloyed platinum-tellurium nanoparticles annealed at 700 °C possessed best acidic tolerance with only 19% decline of mass activities after 1000 cycles potential cycling in 0.5 M H2SO4. The meliorative durability was ascribed with well-structured Pt-Te nanoparticles and Pt-increase skin generated from dealloying process.

In order to obtain the catalyst with Pt isolated-atom surface and high performance towards formic acid electro-oxidation (FAEO), cyclic potential dealloying method was employed for preparing dealloyed PtCu/C (D-PtCu/C) catalysts, and the effect of dealloying parameters on the activity of D-PtCu/C catalysts also were investigated. XRD results show that both of PtCu and D-PtCu catalysts are face-centered cubic (fcc) structure. TEM, XPS and ICP results demonstrate the dissolution of Cu atoms and the formation of core-shell structure. And HRTEM results further exhibit the etched surface of D-PtCu/C catalyst which should be made up of isolated atom and atomic clusters of Pt. By electro-chemical analysis, the performance towards FAEO is extremely enhanced. The onset potential of FAEO on D-PtCu/C is at − 0.1 V (vs. SCE) and only one peak is confirmed at 0.5 V which negatively shifts about 0.19 V compared with the peak of commercial Pt/C (at 0.69 V). The mass activity of optimized D-PtCu/C reaches up to 1253.89 mA mg− 1 Pt at 0.5 V, which is 6.20 times as high as that of Pt/C (202.40 mA mg− 1 Pt). And the specific activity (2.36 mA cm− 2) is 8.43 times of Pt/C (0.28 mA cm− 2). The increased activity should be ascribed to the electronic effect and ensemble effect, which reduce the chemisorption of CO and promote the dehydrogenation process.

Aiming to improve the activity of Pt-based catalysts for formic acid electro-oxidation, dealloyed PtxTey/C catalysts were prepared via electrochemical leaching process. The dealloyed-Pt3Te/C catalyst presented superior activity and stability for formic acid electro-oxidation. The mass activities of dealloyed-Pt3Te/C at 0.25 V and 0.4 V vs. SCE were about 10.6 and 16.5 times as high as that of commercial Pt/C, respectively. It is found that the FAEO on D-Pt3Te/C is mainly through dehydrogenation pathway. The weak CO adsorption, increased electrochemical specific area and ensemble effect are suggested as reasons for the remarkable enhancement.

Apple-derived porous carbon (denoted as APC) is successfully prepared and analyzed as a potential carbon material by hydrothermal carbonization and pyrolysis, which exhibits a high specific surface area and porous structure. Furthermore, nickel–cobalt double hydroxide (Ni–Co DH) is synthesized by design of hybrid nanowires on APC for supercapacitors via a simple hydrothermal process. The fabricated electrode produces a capacitance of 1519 F g−1 at 1 A g−1, and 90.2% of the capacitance is retained after 2000 cycles at a high current density. An asymmetric supercapacitor (ASC) is assembled using the Ni–Co DH@APC as the positive electrode and active carbon as the negative electrode. The ASC exhibits a prominent energy density of 61.2 Wh kg−1 and high power density of 14,400 W kg−1 at 5 A g−1. The desirable electrochemical performance can be attributed to the suitability of APC as a support and the Ni–Co nanostructure constructed on the surface of APC as an effective active material for high-energy and long-life cycling supercapacitor applications. The fabricated composite provides a potential design of low-cost functional carbon materials that can be produced in large scale by using biomass as starting materials.

Novel nanohybrid MgFe2O4 (MFO) supported on carbon black co-doped by nitrogen and sulfur (CNS) was facilely synthesized as an efficient electrocatalyst (namely, MFO/CNS) for oxygen reduction reaction (ORR) in alkaline medium. Structural analysis by X-ray diffraction revealed the formation of MFO and confirmed its spinel structure in MFO/CNS nanocomposite. Transmission electron microscope images showed that the products synthesized by different annealing temperature displayed a diverse particle size and dispersion of active component. Electrochemical results indicated that the MFO/CNS hybrid with the controllable N, S-co-doping shows an enhanced ORR catalytic activity and desired direct four-electron reaction pathway, which is better than MFO and CNS synthesized under the same conditions. The excellent electrochemical performance of MFO/CNS should be attributed to the synergistic effect of MFO and CNS to form a conductive network structure, which offers the increased electrochemical active surface area, the facilitated electron transfer, and effective mass transport between oxygen molecules and active sites. The results demonstrated that the MFO/CNS nanohybrid in this study appears to be a promising cathodic electrocatalyst in alkaline fuel cells.

Atomically dispersed iron–nitrogen–carbon (Fe–N–C) catalyst is a promising candidate to replace Pt for oxygen reduction reaction (ORR). To enhance ORR activity of Fe–N–C catalysts, the density and distribution of isolated Fe–N4 sites should be further optimized. Herein, a ligand–assisted strategy to synthesis of single atomic Fe–N–C derived from Zr–metal–organic frameworks (Zr–MOFs) is proposed. During preparation, –NO2 (from 2–nitroterephthalic acid ligands) in Zr–MOFs not only acts as the anchoring sites to capture Fe–polydopamine (FePDA) source but also plays a crucial role in modulating the Fe − N4 configuration. The resulting SA Fe@ZrO2/NC catalyst consists of FeN4 sites with adjacent ZrO2 in N–doped carbon, in which in–situ introduction of ZrO2 positively enhance O2 adsorption ability. Due to the moderate pore structure, atomically dispersed Fe–N4 active sites, and the strong interface interaction between isolated Fe atoms and ZrO2 nanocluster, the as–prepared catalyst exhibits comparable ORR activity and outstanding stability in alkaline solution. When assembled in a rechargeable Zn–air battery, the battery with SA Fe@ZrO2/NC air electrode delivers a stable open circuit voltage, high–power density (250 mW cm−2) and discharge specific capacity (730 mA h gZn−1). It also demonstrates a long cycle life and good rate performance. Density functional theory calculation results reveals that the adjacent ZrO2 nanocluster modulates the electron structure of Fe atoms in FeN4 sites with an improved ORR process and activity. This work provides a facile strategy for preparing efficient single atomic Fe–N–C catalyst to drive the oxygen reduction reaction in Zn–air batteries.

Engineering the elemental composition and structure of manganese-based cathode materials offer an effective strategy for the development of aqueous zinc ion batteries (AZIBs) with greatly enhanced specific capacity and good stability. In this work, a manganese monoxide (MnO) composite with MnO as the core and some organic intermediate with the active functional group as the outer layer was derived from Mn metal–organic framework (Mn-MOF). Benefiting from the unique structure, active functional groups, and the synergetic effect of core–shell, the obtained MnO-C display superior electrochemical performance, demonstrating specific capacity (727.7 mAh g−1 at 0.1 A g−1) in the (CF3O3S)2Zn aqueous electrolyte and good rate performance (413.8 mAh g−1 at 1.0 A g−1), which is higher than that of MnO2 (331.7 mAh g−1) and commercial MnO (234.5 mAh g−1). Furthermore, the Zn-storage mechanism in MnO-C is systematically studied and discussed via multiple analytical methods. This work provides an idea for the development of electrochemical activation strategies for advanced cathodes of high-performance zinc ion batteries.

The primary task to improve the performance of vanadium redox flow battery (VRFB) is to develop the membranes with high proton conductivity. Herein, a string of sulfonated polyimide (SPI) blend with poly [bis (4,4′-diaminobenzidine-2,2′-disulfonic acid) phosphazene] (PDAP) membranes were designed and prepared. The introduction of PDAP containing amphoteric functional groups not only provides more proton transport groups (–SO3H), but also reach the purpose to prevent the migration of vanadium ions, which is caused by the Donnan repulsion to vanadium ions from N-protonation. Therefore, the prepared membrane exhibits high proton conductivity (up to 1.33 × 10−1 S cm−1 at room temperature) and low vanadium permeability (1.37 × 10−8 cm2 s−1). The performance of VRFB with SPI/0.5% PDAP membrane exhibits a voltage efficiency (VE) of 87.02% and an energy efficiency (EE) of 84.04% at 100 mA cm−2, which were better than that of Nafion 212 (VE: 82.04%, EE: 76.99%). In addition, the VRFB with SPI/0.5% PDAP membrane can be cycled continuously and perfectly for 500 times at 100 mA cm−2 with stable efficiencies. After cycling, the membrane was intact without any defects, and the FTIR spectra and morphology of the membrane did not change significantly. These results prove that the SPI/0.5% PDAP membrane is an ideal membrane in VRFB applications.

A novel three-dimensional (3D) electrocatalyst composite was successfully prepared through a facile hydrothermal method, consisting of tungsten nitride nanosheets with flower-like morphology (WN FNs) and nitrogen-doped carbon black (N–C). Highly crystalline WN FNs were observed to be uniformly distributed in N–C, and remarkably promoted the catalytic activities toward oxygen reduction reaction (ORR) of the N–C. Moreover, the electrochemical results proved that, WN FNs/N–C composite shows a significantly higher ORR activity with a 4-electron transfer pathway and limiting current density of 5.8 mA cm−2 in alkaline solutions. The stability test of the nanocomposite showed less degradation after 5 h and its methanol tolerance also was enhanced compared with Pt/C. The improved performance of the WN FNs/N–C composite can be attributed to its unique configuration and the increased exposure of active sites, which suggests that it could serve as an ideal candidate for developing high performance ORR catalysts.

This work presents a type of hybrid catalyst prepared through an environmental and simple method, combining a pyrolysis of transition metal precursors, a nitrogen-containing material, and a tungsten source to achieve a one-pot synthesis of N-doping carbon, tungsten carbides, and iron/cobalt carbides (Fe/Co/WC@NC). The obtained Fe/Co/WC@NC consists of uniform Fe3C and Co3C nanoparticles encapsulated in graphitized carbon with surface nitrogen doping, closely wrapped around a plate-like tungsten carbide (WC) that functions as an efficient oxygen reduction reaction (ORR) catalyst. The introduction of WC is found to promote the ORR activity of Fe/Co-based carbide electrocatalysts, which is attributed to the synergistic catalysts of WC, Fe3C, and Co3C. Results suggest that the composite exhibits comparable electrocatalytic activity, higher durability, and ability for methanol tolerance compared with commercial Pt/C for ORR in alkaline electrolyte. These advantages make Fe/Co/WC@NC a promising ORR electrocatalyst and a cost-effective alternative to Pt/C for practical application as fuel cell.

A novel sulfonated poly(ether ether ketone) (SPEEK)/TiO2 double-deck membrane which consists of a layer of SPEEK and a layer of TiO2 was prepared and investigated for vanadium redox flow battery (VRB) application for the first time. The physicochemical properties of the SPEEK/TiO2 membrane, including the water uptake, swelling ratio, ion exchange capacity, proton conductivity, VO2 + permeability and ion selectivity are evaluated in detail, compared to the pristine SPEEK membrane and Nafion 117 membrane. The scanning electron microscopy images reveal its double-deck structure and the structural stability with no delamination, and thermogravimetric analysis (TG) identifies its thermal stability. Among all membranes, the SPEEK/TiO2 double-deck membrane possesses lowest vanadium ion permeability (6.66 × 10− 7 cm2 min− 1) and highest ion selectivity (9.46 × 104 S min cm− 3). The VRB single cell with SPEEK/TiO2 double-deck membrane shows higher coulombic efficiency (97.0% vs 93.3%) and energy efficiency (85.8% vs 83.7%) compared to that with Nafion 117 membrane at 60 mA cm− 2. Furthermore, the SPEEK/TiO2 double-deck membrane exhibits highly stable cell performance after 60 times of cycling tests at 60 mA cm− 2 and lower capacity decay rate than that of Nafion 117 membrane. Therefore, the SPEEK/TiO2 double-deck membrane exhibits good potential usage in VRB systems.

Sulfonated poly(ether ether ketone)/poly(vinylidene fluoride)/graphene (S/P/G) composite membrane was prepared through a solution-casting method for a vanadium redox flow battery (VRB), and the weight ratio of high sulfonated poly(ether ether ketone) (SPEEK), polyvinylidene fluoride (PVDF), and graphene was optimized. The preferred S/P/G-7 composite membrane showed the lowest VO2+ permeability and highest ion selectivity compared with other four kinds of cation exchange membranes SPEEK75, heterogeneous PSSA-PE, Nafion 117, and recast Nafion (r-Nafion). The VRB with S/P/G-7 membrane exhibited the higher coulombic efficiency of ∼8% and energy efficiency of ∼4%, but lower capacity loss and self-discharge than that of VRB with Nafion117 membrane during cycling tests, which further indicated the promising prospects of S/P/G-7 composite membrane in VRB application.

This paper presents a facile approach for the synthesis of a novel Pt/graphene-nickel foam (Pt/GNF) electrode composed of flower-like Pt nanoparticles (NPs) and 3D graphene. The fabrication process involved the chemical vapor deposition of graphene onto Ni foam as a substrate and the subsequent growth of Pt NPs via a galvanic replacement reaction without using any seed and organic solvent. The surface morphology and composition of the prepared materials were characterized. Meanwhile, cyclic voltammetry and electrochemical impedance spectroscopy were employed to confirm their typical electrochemical characteristics. The as-prepared nanocomposites displayed enhanced catalytic activity and kinetics toward methanol electro-oxidation. Such an excellent performance can be ascribed to the high dispersion of flower-like Pt NPs and to the exposure of more sites provided by the flower-like structure. The improved stability, decreased charge transfer resistance, and enhanced reaction rate of the nanocomposites promise new opportunities for the development of direct methanol fuel cells.

A blend membrane consisting of sulfonated poly(ether ether ketone), poly(vinylidene fluoride), and tungstophosphoric acid (denoted as SPEEK/PVDF/TPA membrane) has been fabricated and firstly used as ion exchange membrane for vanadium (V) redox flow battery (VRB) application. This composite membrane is characterized by physical and electrochemical methods. The results show that the SPEEK/PVDF/TPA membrane possesses significantly high ion selectivity and low permeability of V(IV) compared with the Nafion 117 membrane. Also VRB single cells with SPEEK/PVDF/TPA membrane show significantly lower capacity loss, higher coulombic efficiency (CE > 93%) and higher energy efficiency (EE > 80%) than that with Nafion 117 membrane. In the self-discharge test, the cells with the SPEEK/PVDF/TPA membrane show better durability. With all the good properties and low cost, the SPEEK/PVDF/TPA membrane shows promising prospects for application in VRB.

In this work, γ-Al2O3 and hydrogen peroxide treated g-C3N4 (O-g-C3N4) were combined through a novel in-situ hydrothermal method to form heterojunction structured photocatalysts. These photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy and photoluminescence spectroscopy (PL). FT-IR results indicate that oxygen functional groups can be grafted on the surface of O-g-C3N4 by hydrogen peroxide treatment. The visible light photocatalytic hydrogen evolution rate was investigated in 10 vol% TEOA aqueous solution. The optimal Al2O3 mass content is set to be 20 wt% and the corresponding hydrogen evolution rate is 1288 µmol/h/g which is approximately 6, 3 folds that of pristine g-C3N4 and O-g-C3N4 respectively and 1.6 folds that of mechanical mixed composite with the same Al2O3 mass content. The photocurrent density–time curves were carried out under visible light illumination for four on–off cycles. The electrochemical impedance spectroscopy (EIS) measurements verified the enhanced separation efficiency of electron–hole pairs. This work raised a new method to form the heterojunction structured photocatalysts and achieved a remarkable improvement of the photocatalytic activity in water splitting for hydrogen under visible light irradiation.

Several organic amines with –NH2 functional groups and inorganic ammoniums with –NH4+ functional groups have been comparatively investigated as stabilizers of the V(V) electrolyte for vanadium redox flow battery (VRB) to improve its stability and electrochemical performance. Thermal stability tests showed that chitosan (CTS) and nonionic-type polyacrylamide (NPAM) additives with –NH2; ammonium thiocyanate (ATC), ferrous ammonium sulfate (FAS) and ammonium ferric sulfate (AFS) additives with –NH4+ could significantly improve the thermal stability of the V(V) electrolyte over a wide temperature range of − 5 °C to 45 °C. The electrochemical behavior of the V(V) electrolyte with these preferred additives was further studied by cyclic voltammetry (CV), steady state polarization, electrochemical impedance spectroscopy (EIS) and charge–discharge test. The results indicated that the electrochemical activity and reversibility for the V(V) electrolyte with the best additive CTS with –NH4+ was significantly improved compared with the additives with –NH2 and pristine one. In addition, the VRB employing the positive electrolyte with CTS exhibited excellent cycling stability and charge–discharge behavior with a high energy efficiency of 82.5%. The N-containing and O-containing functional groups of CTS in the V(V) electrolyte could modify the electrode and further improve the electrochemical performance and cycling stability of VRB.

In this study, a wet refining process for indium purification was developed aiming at the problem that the electrolysis refining method is difficult to remove cadmium, lead (Pb), and tin in indium, so as to reduce the energy-consuming and time-consuming process of smelting at the same time. The original electrolyte made by crude indium (99%) is co-precipitated to remove lead and pre-electrified to remove tin, and then heated to activate indium ions during electrolysis refining to reduce the electrodeposition of Cd2+, and the purity of electrodeposited indium can reach 99.99% after only once electrolysis refining like this. The mechanism of the removal of Pb2+ by co-precipitation is also discussed: 1–6 ppm Pb2+ is in the metastable region (dissolution and crystallization), and cannot nucleate spontaneously, but as long as there is a surface charged solid in the solution, which can provide Coulomb force, Pb2+ can be induced to grow on solid with SO42−, regardless of crystal form, chemical configuration, and ion type. This viewpoint can explain some anomalous phenomena which cannot be explained well by the traditional co-crystallization and co-precipitation theory. In addition, it is the first observed that temperature plays an extremely important role in the separation of In3+ and Cd2+ in the electrolytic refining process. During electrolytic refining at 40 °C, even though the concentration of Cd2+ in the solution is as high as 200+ ppm, the content of cadmium in the electrodeposited Indium meets the standard of 4 N-Indium, while In3+ and Cd2+ are generally considered cannot be removed by electrolytic refining because their electrode potentials are too similar. The mechanism is also explicitly explained: the In3+ electrodepositing process is mainly controlled by activation, and the electrochemical reaction resistance decreased to 1/4 of the original with the increase of temperature, so that the cathode only needs a smaller overpotential to achieve the expected current, reducing the amount of Cd2+ electrodeposition in the cathode.

To improve SPI stability, poly[bis(4-methylphenoxy) phosphazene] (PMPP) was designed and synthesized using polyphosphazene's unique and strong flexibility. A novel sulfonated polyimide (SPI) composite membrane embedded with flexible PMPP chains was prepared for all vanadium redox flow battery applications. SPI/PMPP composite membrane characterizations, such as proton conductivity, vanadium ion permeability, stability, and single cell performance, were thoroughly investigated. PMPP's unique properties not only allow the membrane to exhibit excellent anti-hydrolysis and anti-oxidation stability, but also maintain high proton conductivity and low vanadium ion permeability (as low as 4.81 × 10−7 cm2 min−1). It can also form a rigidity-flexibility network with SPI to improve membrane mechanical properties. It can be deduced that introducing PMPP has achieved many things in one stroke. Results show that the hydrolysis and oxidation stabilities of SPI/PMPP membrane were significantly improved. The SPI/2% PMPP membrane exhibits higher columbic efficiency (CE: 97.52%), voltage efficiency (VE: 84.88%), and energy efficiency (EE: 82.21%) than that of the N212 membrane (CE: 94.97%, VE: 82.04%, EE: 76.99%) at a high current density of 100 mA cm−2. In addition, the charging capacity loss of a battery with a SPI/2% PMPP membrane has also significantly decreased by about 206.70 mAh after 110 cycles at 100 mA cm−2 with the same electrolyte volume compared to a pristine SPI. Meanwhile, the high temperature resistance of SPI/PMPP membrane also shows the possibility of being applied with fuel cells.

Pt and metal oxide hybrid catalysts based on strong metal support interactions have been proved to be an effective way to improve oxygen reduction reaction (ORR) performance of Pt. In this work, Pt/CeO2/CNT-A triple junction interface catalyst was obtained by atomic layer deposition. Compared with Pt/CeO2/CNT-W (wet chemical method) and Pt/C, Pt/CeO2/CNT-A shows the highest catalytic activity and stability for ORR. As expected, the enhanced ORR performance can be attributed to unique triple junction interface structure which Pt has contact with CNT and ultra-small CeO2. Therefore, ALD method could be a promising strategy to construct effective triple junction interface.

Anode slime and its processing residue contains a variety of valuable elements, which are the main source of tellurium and bismuth. A systematic study on the extraction of tellurium and bismuth from processing residue of zinc anode slime and electrodeposition to obtain high purity bismuth was carried out. Sulfation roasting thermodynamics, leaching thermodynamics, and reduction potential involved in the extraction were calculated and used as theoretical guidance for the experiment. In the process of extracting tellurium and bismuth: the minimum amount of sulfuric acid and the appropriate low temperature of sulfation roasting conditions for processing residue of zinc anode slime are explained that the ratio of sulfuric acid to anode slime was 0.54:1, and the temperature was 435 °C. The leaching process of the roasting product was optimized. The optimal water leaching conditions were a liquid to solid ratio of 6:1 and a reaction time of 0.5 h at 25 °C. The optimal alkali leaching condition is 10% NaOH liquid to solid ratio of 6:1 and reaction time of 0.5 h at 25 °C. Tellurium and bismuth were separated, and tellurium was enriched from a low content of anode slime raw materials. The recovery rate of tellurium and bismuth were 84.9% and 97.1%, respectively. The reduced deposition process of bismuth ions on the cathode was characterized by cyclic voltammetry in the nitric acid. In the stable deposition state, electrodeposition overpotential of the bismuth ion on the titanium plate was 0.1068 V. Tributyl phosphate (TBP) was used as extraction solvent and nitric acid solution was used as stripping solution to purify the impurities in the basic bismuth sulfate. After extraction process, the removal rates of tellurium (Te), arsenic (As), copper (Cu), and antimony (Sb) were 96.5%, 93.3%, 99.1% and 100%, respectively. The content of other impurity elements also reduced greatly. The electrical separation process further reduced the content of impurities in the electrolyte, in which the concentration of tellurium was reduced to less than 1 ppm. A standard-compliant high purity elemental bismuth was obtained by electrodeposition from purified electrolyte.

A novel sulfonated poly(ether ether ketone)/triphenylamine hybrid membrane with various triphenylamine loadings (1%, 2% and 5%) has been successfully fabricated. Optimum triphenylamine loading was confirmed by exploring the physicochemical properties and morphology of different membranes. The hybrid membrane exhibited lower vanadium permeability than pristine SPEEK membranes due to the acid–base interaction between amine groups and sulfonated groups. Introduction of triphenylamine also improved the proton conductivity because the nitrogen atom of triphenylamine can be protonated and contribute to the proton transfer. As the result, the hybrid membrane demonstrated higher ion selectivity compared with SPEEK and Nafion115 membranes. The VRFB single cell with SPEEK/TPAM-1% membrane showed better performance compared to a Nafion115 membrane at the current density of 60 mA cm−2. The SPEEK/TPAM hybrid membrane has great potential for VRFB application.

A novel three-dimensional graphite-coated nickel foam (GNF) was synthesized by the chemical vapor deposition (CVD) method, and palladium nanoparticles (Pd NPs) were successfully synthesized on a GNF support by metal atomic layer deposition (ALD) technology for the first time. The physicochemical properties of the as-prepared catalysts were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma-atomic emission spectrometry (ICP). Results showed that the Pd NPs with ultralow loading (below 50 μg cmPd−2) were uniformly dispersed on the GNF support, and the as-prepared catalysts presented the highest catalytic activity toward ethanol electro-oxidation (the peaking current density was about 39.97 mA cm−2) in alkaline media. In particular, it was found that the morphology and content of graphite of the GNF will greatly affect the dispersion of the ALD Pd NPs. When the CVD time for preparing the GNF was 10 min, the as-prepared catalyst presented a higher dispersity of Pd NPs and catalytic activity toward ethanol electro-oxidation than that of other as-prepared catalysts. The effect of the ALD cycle for Pd NPs growth and its performance was also investigated. When the cycle of ALD Pd was 450, the peaking current density of the as-prepared catalysts was about 2.64 times as high as that of commercial Pd/C to ethanol electro-oxidation. Herein, there is a promising application prospect for the prepared Pd/GNF nanocomposite as an electrocatalyst toward ethanol electro-oxidation in alkaline media.

In order to obtain a loaded Pt-based catalyst with enhanced high activity and stability towards formic acid electro-oxidation (FAO), PtTe nanoparticles loaded on graphene oxide (GO) were fabricated by a facile and scalable method. XRD and HRTEM results show that the morphology of PtTe particles could be affected by the additive amount of GO and Te. It is observed that the supported PtTe particles are cubic. The XPS results show the change in the Pt electronic structure after the incorporation of Te, which impedes the chemisorption of the CO intermediate and promotes the dehydrogenation pathway of FAO. By electrochemical analysis, the performance towards FAO is greatly enhanced. The mass activity of PtTe/GO-67 is [Formula: see text] at 0.45 V (versus SCE), which is 11.5 times as high as that of Pt/C [Formula: see text] The incorporation of Te atoms and the content of GO are two major parameters for tuning the crystal structure and morphology and enhancing catalytic activity.

Iron selenide (FeSe) is a promising anode material for lithium-ion batteries (LIBs), with high specific capacity, high tap-density and good electrical conductivity. However, the rapid decay of specific capacity seriously impedes its practical application, which results from the large volume change during charge-discharge cycles damaging electrode structure. Here, the yolk-shell FeSe@C nanobox is successfully synthesized via a novel method of selenization to the core after carbonization to the shell with chemical vapor deposition (CVD). The space between the core and the shell helps to release the volume expansion during lithiation/delithiation processes, and FeSe is kept inside the carbon microboxes without breaking the shell. Therefore, the yolk-shell FeSe@C displays outstanding electrochemical performance as the anode of lithium-ion batteries, which remained a specific capacity of 871.6 mAh g−1 after 250 cycles at a current density of 1 A g−1 and at a large current density, 10 A g−1, the specific capacity can still reach 430.4 mA h g−1. This novel yolk-shell structure and the synthesis strategy could be employed in other anode materials for high-performance lithium-ion batteries and other electrochemical devices.

Several ionic organic compounds have been employed as additives of the V(V) electrolyte for a vanadium redox flow battery (VRB) to improve its stability and electrochemical activity. Stability of the V(V) electrolyte with and without additives was investigated with an ex situ heating/cooling treatment over a wide temperature range of −5 °C to 60 °C. It was found that cationic organic compounds could significantly improve the stability of the V(V) electrolyte over a wide range of temperatures. Their electrochemical behavior in the V(V) electrolyte was further studied by cyclic voltammetry (CV) and steady state polarization. The results showed that the electrochemical activity, including the reversibility of the electrode reaction, the diffusivity of V(V) species, polarization resistance of V(V) species, and the flexibility of charge transfer for the V(V) electrolyte with these additives were all improved compared with the pristine solution. The VRB employing the positive electrolyte with cationic organic compounds as additive exhibited excellent charge–discharge behavior with an average energy efficiency of more than 80% at a current density of 20 mA cm−2. XPS spectra illustrated that the addition of CHPTAC introduced more oxygen-containing and nitrogen-containing functional groups, which improved the electrochemical performance and cycling stability of the VRB.