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The electrochemical performance of solid oxide cells (SOCs) is investigated under both fuel cell and electrolyzer operations to understand their asymmetric behavior between the two operation modes. The current–voltage and electrochemical impedance characteristics of a hydrogen-electrode-supported cell are experimentally analyzed. Also, a numerical model is developed to reproduce the cell performance and to understand the internal resistances of the cell. Partial pressures of supplied gas and load current are varied to evaluate their effects on the cell performance. The gas partial pressures of hydrogen and steam supplied to the hydrogen electrode are kept equivalent so that the cell performance can be fairly compared between the two operation modes when the same current is applied. It is found that the origin of the asymmetry is mostly from the hydrogen electrode; both activation and concentration overpotentials show asymmetric behavior particularly at high current densities. A numerical experiment is also conducted by deliberately changing parameters in the model. Asymmetry in the activation overpotential is found to be originated from the non-identical charge-transfer coefficients in the Butler–Volmer equation and also from the non-uniform gas concentration formed in the hydrogen electrode under current-biased conditions. On the other hand, asymmetry in the concentration overpotential is associated with the non-equimolar counter diffusion of hydrogen and steam caused by the effect of Knudsen diffusion. Therefore, enhancing gas transport in the hydrogen electrode and reducing the contribution of Knudsen diffusion are effective approaches to reduce asymmetry not only in the concentration overpotential but also in the activation overpotential.

Lithium (Li) metal is an attractive anode material with high capacity (3860 mAh g−1) and low potential (−3.04 V vs. standard hydrogen electrode) that shows highly promising for applications requiring high energy density. However, the low electrochemical potential of Li metal makes it extremely reactive and inevitably forming a native oxidized layer in the ambient environment and repeatedly being consumed when exposed to liquid electrolytes. It is therefore beneficial to replace the poorly controlled native passivation layer with a tailored artificial SEI to improve interface management between Li and electrolyte and enhance the stability of Li metal battery. Here, we use an integrated glovebox-atomic layer deposition (ALD)- X-ray photoelectron spectroscopy (XPS) setup to in-situ investigating the pristine Li surface and the surface composition after Ar, H2, O2, N2 and NH3 plasma treatment processes. We find that the pristine Li foil is naturally being covered with a native oxidized layer, which is mainly composed of LiOH, Li2O and Li2CO3. These investigated plasmas can efficiently remove the oxidized layer from the Li metal surface, in which metallic Li surface is obtained after Ar or H2 plasma treatments, where Ar plasma is more efficient. While O2 plasma treatment produces a Li2O layer, and N2 or NH3 plasma treatment leads to a Li3N (including a certain amount of LiON) layer on the Li surface. When employing the representative metallic Li (by Ar plasma treatment), Li2O layer coated Li (by O2 plasma treatment) and Li3N layer coated Li (by N2 plasma treatment) foils as electrodes in symmetric Li metal batteries, the Li3N coated Li electrode exhibits much higher stability than that of metallic and Li2O layer coated Li foils. Improved electrochemical performance has also been achieved in LiMn2O4 (LMO)||Li full cells using Li anode with Li3N protective coating layer. Our work reveals the detailed process of surface engineering of Li metal anodes with plasma treatments by in vacuo XPS, which may also be extended to other gas-treatment or plasma-treatment for stabilization of high energy density Li metal anodes and other metal-based anodes.

Li metal anodes (LMAs) has attracted extensive research interest because of its extremely high theoretical capacity (3860 mAh/g) at low redox potential (−3.04 V vs. standard hydrogen electrode). However, the extremely high chemical reactivity and the intrinsic “hostless” nature of LMAs bring about serious dendritic growth and dramatic volume change during the plating/strapping process, thus resulting in poor Coulombic efficiency, short lifespan, and severe safety concerns. Of various strategies, the construction of three-dimensional carbonaceous scaffolds for LMAs can substantially reduce the local current density, inhibit Li dendrite growth, and accommodate volume variation. Electrospinning is a simple yet effective strategy to fabricate carbon nanofibers (CNFs), which have been regarded as promising skeletons for LMAs, owing to their large surface areas, good electrical conductivity, and high porosity. In this Mini Review, we briefly introduce the fabrication of CNFs using electrospinning and the modification of CNFs. We highlight the recent advances in electrospun CNF skeletons for LMAs, including pure CNF and CNF-based composite scaffolds. Finally, we discuss the remaining challenges of electrospun CNF scaffolds for LMAs and provide possible solutions to push forward the advancement in this field.

Layered-type metal phosphates of BaNb2-xTaxP2O11 (x = 0, 0.5, 1.0, 1.5, and 2.0) were synthesized using a solid-state reaction method. The photophysical, optical, and photocatalytic hydrogen production properties of the resulting powders were investigated for the first time. Phase-pure and homogeneous powders with irregular morphologies were obtained at a calcination temperature of 1200 °C. As the Ta content increased, the interlayer distance along the c-axis increased by up to 0.14%. Additionally, the optical bandgap values increased from 3.32 to 3.59 eV. The energy band positions were estimated from the Mott–Schottky measurements. BaNb2P2O11 (x = 0) exhibited the lowest conduction band edge position (−0.14 V vs. the normal hydrogen electrode, NHE), which is located above the water reduction potential (0.0 V vs. NHE). In comparison, BaTa2P2O11 (x = 2.0) exhibited the highest conduction band edge position (−0.29 V vs. NHE), comparable to that of TiO2. The photocatalytic activity for hydrogen produced from splitting water was measured under ultraviolet light irradiation. Notably, BaTa2P2O11 exhibited the highest activity (7.3 μmol/h), which was 15 and 10 times larger than BaNb2P2O11 (0.5 μmol/h) and nano-TiO2 (0.7 μmol/h), respectively. The activity of BaTa2P2O11 increased to 24.4 μmol/h after deposition of the NiOx co-catalyst (1 wt.%), which remained stable during continuous operation (~35 h).

As a new type of energy conversion device, solid oxide electrolysis cell (SOEC) has attracted much attention in recent years because of its advantages such as high efficiency and unlimited capacity. At present, SOEC mainly has such issues as the element diffusion or delamination at oxygen electrode/electrolyte interface under high oxygen partial pressure, which limits its operation lifetime. In this paper, La1-xCaxFeO3-δ materials without Sr and Co were prepared by glycine-nitrate combustion method as SOEC oxygen electrodes. It is found that La0.6Ca0.4FeO3-δ (LCF64) has excellent electrical conductivity and has a coefficient of thermal expansion matching with SSZ electrolyte. The hydrogen electrode supported single cells with structure of LCF64-GDC (6:4) | GDC | SSZ | NiO-SSZ active layer | NiO-YSZ transition layer | NiO-YSZ supported layer were prepared by tape casting and co-firing method showed good electrochemical performance in SOEC mode. The electrolysis current density is 457.46 mA cm-2 with 60% H2O-H2 atmosphere and 1.3 V applied voltage at 800 °C. During the constant voltage (1.3V) electrolysis process, the SOEC showed an acceptable stable current density of approximate 280 mA cm-2 for more than 60 h.

Summary Lithium metal electrodeposits in the form of irregular morphological features, loosely termed dendrites, on planar anode substrates. The deposits may lead to rapid battery failure and safety concerns. Due to the highly reducing nature of Li (−3.04 V versus standard hydrogen electrode [SHE]), a solid electrolyte interphase (SEI) inevitably forms at the electrode/electrolyte interface, which regulates the subsequent electrodeposition of Li. Rational design of the chemical, mechanical, and ion transport properties of SEI plays an important role in determining the morphology of electrodeposited metals. We report on using initiated chemical vapor deposition (iCVD) to create ultrathin conformal zwitterionic polymeric interphases with precise thicknesses in the range of 10–500 nm. It was found that zwitterionic moieties are able to tune the solvation environment of the lithium cation at the electrode/electrolyte interface, enabling compact, planar deposition of the lithium metal. These findings provide new directions for designing ionic polymeric interphases for metal anodes.

Lithium metals offer great promises to achieve higher energy density beyond conventional lithium-ion batteries (LIBs) because of its ultrahigh specific capacity (3860 mAh g−1) and the lowest reduction potentials (-3.04 V vs. standard hydrogen electrode). Unfortunately, the application of lithium metal anode has been long-standingly handicapped by uncontrollable dendrite growth, which induces instable solid electrolyte interface (SEI), performance degradation and thermal runaway. Herein, a compositionally favorable and structurally robust dual-protective layer (DPL) is proposed, where at the bottom, in-situ formed LiCl film provides sufficient rigidity (6.5 GPa) and low Li+ diffusion barriers (0.09 eV) against dendrite growth. The poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) gel-electrolyte as the top layer is rationally selected with high flexibility to accommodate volume variation. Due to the synergy of DPL, the instability of interface is ultimately regulated to favor an extremely stabilized SEI with enhanced Li+ diffusion kinetics. Depth profiling of X-ray photoelectron spectroscopy (XPS) revealed a spontaneously-formed gradient SEI hierarchy, a first-of-this-kind structure that enables long-term cycle stability and high rate capability. Cryo-electron microscopy (cryo-EM) provides direct proof on the formation of halide-rich SEI interlayers that strengthen the interfacial stability during cycles. As a consequence, dendrite-proof lithium deposition, critical Li+ flux and fast ion-diffusion kinetics have been synergistically achieved to greatly improve the high-rate cycle stability (10 mA cm−2), high Coulombic efficiency (99.5%), and prolonged cycle lifespan (1600 h) for lithium metal batteries (LMBs). The design of DPL from this contribution has opened up opportunities of lithium chlorides in purpose of constructing dendrite-free and Li+ permeable interface, and provided insights for the realization of high energy density LMBs.

Lithium metal is considered a promising anode material for high-energy-density rechargeable batteries because of its high specific theoretical capacity (3860 mAh g−1), low mass density (0.534 g cm−3), and low electrochemical redox potential (-3.04 V vs. the standard hydrogen electrode). However, the high reactivity of Li with the electrolyte leads to the formation of an unstable solid electrolyte interphase (SEI) and continuous side reactions. Also, the non-uniform lithium-ion flux and infinite volume expansion of Li metal cause the growth of Li dendrites. These pose significant safety challenges and cause rapid capacity fading of the lithium metal batteries (LiMBs). To resolve these issues, a low-cost, easily processed, lightweight, high-performance carbon-based porous matrix is considered promising to host Li metal deposition. The three-dimensional (3D) porous nano/microstructured carbon provides sufficient space for Li accommodation during Li plating, buffers the volume changes during Li plating/stripping, and lowers the effective current density contributing to dendrite-free Li deposition. Besides, the outstanding electrochemical and mechanical stability, flexibility and the high electronic conductivity enable the nano/microstructured carbon to serve as both Li host and current collector. The development of 3D carbon/Li composite by mechanical roll-press techniques not only eliminates the complex and risky procedure of making carbon/Li composite based on Li plating or molten Li infusion but also stabilizes the capacity at higher Li plating/stripping rates. Recently, there is an advancement in the lithiophilic decorations of 3D structure to introduce sufficient nucleation sites and the development of artificial SEI on top of the 3D matrix to suppress Li dendrite formation. Such 3D structural modifications create a uniform electric field, lower the Li nucleation overpotential, provide strong mechanical and chemical stability, and stabilize the interface thereby inhibiting the degradation of lithium and the electrolyte. In this review, we summarize the research progress on porous carbon/Li composites in terms of materials type, structure, fabrication technique, their electrochemical battery performance, and identify the critical challenges that need to be addressed for high-energy-density practical LiMBs.

Due to the rapid development of Anion-Exchange Membrane Fuel Cell (AEMFC), the development of non-noble metal electrocatalysts for hydrogen oxidation (HOR) in alkaline media has become urgent. Herein, the low-cost Mo–Co2P/CoP catalyst was synthesized, which can be used as a HOR electrocatalyst in alkaline medium. The improved performance is due to the surface modification of Mo species exposed to air oxidized, and the addition of Mo oxidized species accelerated the alkaline hydrogen electrode kinetics process. The development of active, inexpensive and stable HOR catalysts is of great significance for the commercialization of AEMFC.

Mesoporous cobalt oxide/nickel foam (NF) is got by a simple chemical method, and a glycerin-based electrolytic cell is rationally assembled with CoO/NF, in which glycerin-KOH aqueous solution is used as electrolyte. Herein, the influence of anodic glycerin oxidation on cathodic hydrogen production is investigated mainly. At 1.35 V vs. reverse hydrogen electrode (RHE), CoO/NF electrode exhibits a current density of 235.71 mA cm−2 for glycerin oxidation, which is about 2.5 times higher than that over Co3O4/NF. For glycerin oxidation, the Tafel slope (189 mV dec−1) over CoO/NF is much lower, compared to that (286 mV dec−1) over Co3O4/NF, demonstrating the robust electrocatalyic reaction kinetics over CoO/NF. For glycerin-contained electrolytic cell, a cell voltage (1.672 V) is needed to reach 50 mA cm−2, which is obviously lower than that (1.975 V) for conventional electrolytic cell. It is obvious that for glycerin-contained electrolytic cell, the required cell voltage has obviously decreased by 0.303 V. This work demonstrates that the substitution of glycerin oxidation for sluggish four-electron OER reaction can greatly promote water electrolysis to hydrogen production. Moreover, this design can not only degrade environmental pollutants, but also produce clean energy, and the reported strategy is obviously environment-benign and cost-effective.

Designing low-cost, highly efficient, and durable electrocatalysts for carbon dioxide reduction reaction (eCO2RR) to value-added chemicals is an appealing approach to balance the global carbon emission. Heterogeneous molecular catalysts is emerging as an important area for CO2 utilization. Herein, a series of atomically isolated transition metal-N4 sites anchored on porphyrin framework (TM/PRF) molecular catalysts are employed as electrocatalysts for eCO2RR because of their well-defined structure, the versatility and relatively low cost, and remarkable activity, which allow the establishment of precise structural model for a better understanding of the CO2 reduction mechanism. Based on density functional theory calculations and the computational hydrogen electrode model on 27 candidates, we propose a number of TM/PRF (TMs = Ni, Co, Mn, Cu, Ag, Au, Zn, Pd, Ti, V, Cr, Ta, W), which show promise of highly active and selective catalysts for carbon monoxide, formic acid, methane and methanol production, while simultaneously suppress competing hydrogen evolution reaction. Studies have shown that the TM center plays a crucial role in determining the catalytic performance of the material. And the TM/PRF molecule tends to stabilize different radical intermediates at the TM site. Thus, when reacted with a greater number of electrons, highly reduced products are formed. Among the different TM/PRF materials, Ta/PRF and W/PRF have been shown to produce CH3OH selectively at low overpotentials (0.39 and 0.58 V), whereas Ti/PRF has been found as highly selective toward CH4 production with low overpotential of 0.58 V, outperforming most known electrodes. The calulation of activation energy and the d-band center reveal that Cr/PRF shows higher catalystic activity in comparison with other TM/PRF. The advantages of the outstanding selectivity of products, the reduced overpotentials and the higher activity of catalyst allow these new systems TM/PRF (TMs = Ta, W, Ti, Cr) to be promising catalysts, which will motivate more fundamental mechanism studies and technological applications for eCO2RR.

Y-doped BaZrO3 ( BaZr 1 − x Y x O 3 − δ , or “BZY”), a proton-conducting ceramic featuring high bulk conductivity and good chemical stability, is a promising electrolyte material for solid oxide electrolysis cells. Further doping with Ce and/or Yb (creating materials “BCZY” and “BCZYYb”) can improve conductivity and sintering properties, but at significant penalty to cells’ faradaic efficiency (FE). Studies have proposed that reduction of lattice Ce can occur in the hydrogen electrode, which consumes some hydrogen produced by the hydrogen evolution reaction, leading to decreased FE. Despite studies suggesting this phenomenon, the mechanism is largely unknown. We developed a multiphysics model to study the transport of multiple defect species and the performance of BZY, BCZY, and BCZYYb, capturing the tradeoff between enhanced performance at the cost of FE for BCZY and BCZYYb electrolytes compared to BZY. We also found that increasing the water content of the anode gas supply lowers the current output of the cell but results in better FE. The model, which uses several parameters previously unavailable in the literature, was validated to experiments varying temperature, steam water content, and electrolyte material, as well as two performance metrics (performance curves and FE). Results verify and explain observed trends, informing future work on Ce-doped BZY electrolytes.

Molybdenum doped strontium ferrite, Sr2Fe1.5O0.5O6 (SFM), is a promising perovskite-type hydrogen electrode material in solid oxide cells (SOCs), but usually suffers from insufficient electro-catalytic activity. Herein, Ni nanoparticles with high electro-catalytic properties have been infiltrated into SFM scaffold to form Ni-SFM electrode with high electro-catalytic activity for power generation and CO2 electro-reduction. Pre-sintering temperature and Ni loading of Ni-SFM electrodes have been systematically investigated to minimize the electrode polarization resistance (Rp). Rps of bare SFM electrode vary significantly with pre-sintering temperature, and the lowest Rp value of 1.04Ωcm2 is obtained for bare SFM electrode pre-fired at 1050 °C. Moreover, a significantly reduced Rp value of 0.32Ωcm2 is achieved at 800 °C after Ni infiltration. Additionally, three-dimensional microstructure of Ni-SFM electrode is simulated numerically, and geometric properties including Ni/SFM/gas triple-phase-boundaries (TPBs) length, Ni/SFM interfacial area, and Ni surface area are calculated under various Ni loadings to correlate electrode microstructure with electrode performance, revealing that the electrode performance are strongly affected not only by the TPBs but also the interface area. Enhanced electrochemical performance indicate that Ni-SFM electrode is a promising high-performance hydrogen electrode for SOCs application.

Cocatalysts play important roles in improving the activity and stability of most photocatalysts. It is of great significance to develop economical, efficient and stable cocatalysts. Herein, using Na2CoFe(CN)6 complex as precursor, a novel noble-metal-free FeCo@NGC cocatalyst (nano-FeCo alloy@N-doped graphitized carbon) is fabricated by a simple pyrolysis method. Coupling with g-C3N4, the optimal FeCo@NGC/g-C3N4 receives a boosted visible light driven photocatalytic H2 evolution rate of 42.2 μmol h−1, which is even higher than that of 1.0 wt% Pt modified g-C3N4 photocatalyst. Based on the results of density functional theory (DFT) calculations and practical experiment measurements, such outstanding photocatalytic performance of FeCo@NGC/g-C3N4 is mainly attributed to two aspects. One is the accelerated charge transfer behavior, induced by a photogenerated electrons secondary transfer performance on the surface of FeCo alloy nanoparticles. The other is related to the adjustment of H adsorption energy (approaching the standard hydrogen electrode potential) by the presence of external NGC thin layer. Both factors play key roles in the H2 evolution reaction. Such outstanding performance highlights an enormous potential of developing noble-metal-free bimetallic nano-alloy as inexpensive and efficient cocatalysts for solar applications.

Due to the increasing demands for energy storage devices with higher energy density, lithium (Li) metal is considered to be the ultimate choice as an anode material because it has a high theoretical capacity (3860 ​mAh ​g−1) and the lowest reduction potential (−3.04 ​V versus standard hydrogen electrode) among all the alkali metals. Despite these advantages, repeated Li plating/stripping during cell operation leads to dendritic Li and the formation of irreversible Li (dead Li), leading to internal short-circuits and capacity fading. These fundamental problems cause safety issues and cell failure, so they must be resolved to commercialize Li-metal anode. Many in-depth studies are ongoing to solve these drawbacks through a variety of approaches, such as the formation of artificial solid-electrolyte interphase (SEI), inserting an interfacial layer between the electrolyte and electrode, demonstrating three-dimensional structured electrodes, and using stable host structures to store Li-metal. In this Review, we focus on using host materials to store Li-metal among various strategies, which may be regarded as an alternative method but is very feasible. Also, we propose porous carbon materials derived from zeolitic imidazolate frameworks (ZIFs) as the host materials due to their suitable properties for Li-metal storage. To advance progress towards practical application, the Li-metal storage capacity of porous materials is mathematically inferred, and further strategies are discussed for improving the storage capacity in this regard. Finally, we presented a perspective that paves the way for applying host materials to anodes of practical Li-metal battery.

Lithium (Li) metal has been considered as the ultimate anode material for next-generation rechargeable batteries due to its ultra-high theoretical specific capacity (3860 mAh g−1) and the lowest reduction voltage (−3.04 V vs the standard hydrogen electrode). However, the dendritic Li formation, uncontrolled interfacial reactions, and huge volume variations lead to unstable solid electrolyte interphase (SEI) layer, low Coulombic efficiency and hence short cycling lifetime. Designing artificial solid electrolyte interphase (artificial SEI) films on the Li metal electrode exhibits great potential to solve the aforementioned problems and enable Li–metal batteries with prolonged lifetime. Polymer materials with good ionic conductivity, superior processability and high flexibility are considered as ideal artificial SEI film materials. In this review, according to the ionic conductive groups, recent advances in polymeric artificial SEI films are summarized to afford a deep understanding of Li ion plating/stripping behavior and present design principles of high-performance artificial SEI films in achieving stable Li metal electrodes. Perspectives regarding to the future research directions of polymeric artificial SEI films for Li–metal electrode are also discussed. The insights and design principles of polymeric artificial SEI films gained in the current review will be definitely useful in achieving the Li–metal batteries with improved energy density, high safety and long cycling lifetime toward next-generation energy storage devices.

Ni–La2O3 cermet hydrogen electrode having almost no ionic conductivity still exhibits excellent electrochemical performance owing to the hydrogen spillover process from high hydrogen adsorption capability on the La2O3 surface. In this work, we develop Ni–La2O3 cermet hydrogen electrode originating from the in-situ decomposition of the La2NiO4+δ(LNO) oxide, and then perform the electrochemical properties for quasi-symmetrical solid oxide fuel cells (Q-SSOFCs), which own YSZ electrolyte support wrapped GDC barrier layer. The area specific resistance (ASR) of LNO air electrode increases from 2.09 to 7.41 Ω cm2, with the temperature of decreasing from 800 to 600 °C. The electrochemical performances of Q-SSOFCs with Ni–La2O3 cermet hydrogen electrode and LNO air electrode are characterized, and the values of the peak power density and the electrode polarization resistance (Rp) of the symmetrical electrodes measured at 800 °C are 245.18 mW cm−2 and 0.61 Ω cm2. These results indicate that the hydrogen spillover process of Ni–La2O3 cermet hydrogen electrode can greatly promote the hydrogen oxidation reaction.

Metallic lithium (Li) is one of the most potential anode materials in the near future, because of its high theoretical specific capacity (3865 mAh/g), low potential (−3.045 V vs standard hydrogen electrode (SHE)) and low density (0.534 g/cm3). However, fatal dendritic Li growth is the bottleneck of the development of Li anode. In this contribution, we reported a titanium nitride (TiN) nanoparticle additive to guide Li deposition uniformly, hence dead Li and dendritic Li are effectively reduced. There are more nucleation sites on the surface of the electrode due to the stronger adsorption of Li ions on each facet of TiN, and TiN nanoparticles play the role of seeds of Li deposition. The half cells cycling in additive electrolyte exhibit an average Coulombic efficiency (CE) of 97.19% for 270 cycles on plane copper (Cu) electrode and an excellent high average CE of 99.01% for 300 cycles on three-dimensional (3D) carbon paper (CP) electrode at 1 mA/cm2 and 1 mAh/cm2. Li–S full cells equipped with such TiN nanoparticles additive electrolyte deliver great enhanced cycling and rate performance. This work provides a new insight to suppress Li dendrite and realizing high performance of Li metal batteries.

Improving the slow kinetics of alkaline hydrogen electrode reactions, involving hydrogen oxidation and evolution reactions (HOR/HER) is highly desirable for accelerating the commercialization of alkaline exchange membrane-based fuel cells (AEMFCs) and water electrolyzers (AEMWEs). However, fundamental understanding of the mechanism for HOR/HER catalysis under alkaline media is still debatable. Here we develop an amorphous tungsten oxide clusters modified iridium-tungsten nanocrystallines (IrWOx) which exhibited by far the highest exchange current density and mass activity, about three times higher than the commercial Pt/C toward alkaline HOR/HER. Density functional theory (DFT) calculations reveal the WOx clusters act as a pivotal role to boost reversible hydrogen electrode reactions in alkaline condition but via different mechanisms, which are, hydrogen binding energy (HBE) mechanism for HOR and bi-functional mechanism for HER. This work is expected to promote our fundamental understanding about the alkaline HOR/HER catalysis and provide a new avenue for rational design of highly efficient electrocatalysts toward HOR/HER under alkaline electrolytes.

(La,Sr)(Ti,Ni)O3 compounds have been characterized as air and hydrogen electrode for symmetrical Solid Oxide Cells. While the materials are thermomechanically compatible with 8YSZ electrolyte, the reactivity tests confirm the formation of an insulating pyrochlore La2Zr2O7, redhibitory for the electrochemical properties. Concerning the electrical behavior, a Ti/Ni = 50/50 ratio is the best option for high electrical conductivity in both air and hydrogen, in view of the targeted application as symmetric cell electrode. The electrochemical performance of La0.875Sr0.125Ti0.5Ni0.5O3 (25LSTN50) material is similar to the materials that have been proposed in literature for SOCs cathode and anode at the same time, but the polarization resistances are still higher than the state-of-the-art hydrogen or air electrodes of classical asymmetric cells.

Summary Li-metal anode with ultrahigh capacity (3,860 mAh/g) and lowest redox potential (−3.04 V versus standard hydrogen electrode) holds the key in advancing the next-generation high-energy-density batteries. The intrinsic defects of hyper-reactivity, dendritic growth, large volume change, and poor wettability on substrate, however, impede its practical applications. Recently, Li-metal-based composite (LMC), made by compositing metallic Li with various functional materials, has been proposed as an alternative to Li-metal anode, exhibiting unique physicochemical properties and excellent performances. To this end, we summarize recent advances in the synthesis, structure, properties, and electrochemical performance of LMC in terms of different functional materials. A special focus has been placed on the wetting behavior of Li metal with different carbons and the fascinating compositing reactions for LMC. We conclude with a discussion on the prospects and essential research directions for exploiting LMC from the fundamental research and practical application point of view. It is expected that this review will encourage Li-metal batteries to step forward to real applications.

Lithium (Li) metal, possessing an extremely high theoretical specific capacity (3860 mAh/g) and the most negative electrode potential (−3.040 V vs. standard hydrogen electrode), is one the most favorable anode materials for future high-energy-density batteries. However, the poor cyclability and safety issues induced by extremely unstable interfaces of traditional liquid Li metal batteries have limited their practical applications. Herein, a quasi-solid battery is constructed to offer superior interfacial stability as well as excellent interfacial contact by the incorporation of Li@composite solid electrolyte integrated electrode and a limited amount of liquid electrolyte (7.5 μL/cm2). By combining the inorganic garnet Al-doped Li6.75La3Zr1.75Ta0.25O12 (LLZO) with high mechanical strength and ionic conductivity and the organic ethylene-vinyl acetate copolymer (EVA) with good flexibility, the composite solid electrolyte film could provide sufficient ion channels, sustained interfacial contact and good mechanical stability at the anode side, which significantly alleviates the thermodynamic corrosion and safety problems induced by liquid electrolytes. This innovative and facile quasi-solid strategy is aimed to promote the intrinsic safety and stability of working Li metal anode, shedding light on the development of next-generation high-performance Li metal batteries.

Potassium (K) metal is the “super star” among all the anode materials for potassium-ion batteries because of its merits such as large abundance (~0.0017 ​wt %), high theoretical specific capacity (687 mAh g−1) and low electrochemical potential (−2.93 ​V vs. the standard hydrogen electrode, SHE). Nevertheless, challenges such as extremely high reactivity, large volume change, unstable interface and uncontrollable growth of K dendrites hinder its further development and practical application. Various effective tactics have been put forward to solve the issues of K metal anodes in recent years. Herein, we detailedly summarize the recent strategies for stable and dendrite-free K metal anodes such as designing a host, interfacial engineering, replacing pure K metal with K-based alloys, modifying liquid electrolyte and replacing liquid electrolyte with solid-state electrolyte. We also proposed some perspectives and outlooks. We believe this review can attract related researchers and provide some help for the future development of K metal anodes.

To promote the application of traditional (La0.8Sr0.2)0.95MnO3-δ-YSZ (LSM-YSZ) oxygen electrodes to both solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) modes at intermediate temperatures, we select PdO as the catalyst and ZrO2 as the PdO stabilizer to decorate the LSM-YSZ. The high active PdO particles enhance the electrocatalytic activity, and stable ZrO2 can hinder the growth and agglomeration of the PdO particles. PdO and ZrO2 are co-impregnated into the LSM-YSZ to form a nano-structured PdO/ZrO2 -LSM-YSZ composite electrode. At 750 °C, the obtained cell attains a power density peak of 1.114 W cm−2 in SOFC mode and shows significant improvement of the cell with LSM-YSZ composite oxygen electrode. As a SOEC, when the water content is 90 vol%AH (absolute humidity) at the hydrogen electrode, the cell exhibits an extraordinary current density of 2.322 A cm−2 under applied voltage of 2.0 V at 750 °C. Moreover, the cell shows notable long-term stability during water electrolysis. Therefore, this study demonstrates that the nano-structured PdO/ZrO2 -LSM-YSZ based material as a high active and stable oxygen electrode can greatly promote the application of LSM-YSZ electrode in reversible solid oxide electrolysis cell (RSOCs) field.

Electrochemical conversion of CO2 into fuels is a promising means to solve greenhouse effect and recycle chemical energy. However, the CO2 reduction reaction (CO2RR) is limited by the high overpotential, slow kinetics and the accompanied side reaction of hydrogen evolution reaction. Au nanocatalysts exhibit high activity and selectivity toward the reduction of CO2 into CO. Here, we explore the Faradaic efficiency (FE) of CO2RR catalyzed by 50 nm gold colloid and trisoctahedron. It is found that the maximum FE for CO formation on Au trisoctahedron reaches 88.80% at −0.6 V, which is 1.5 times as high as that on Au colloids (59.04% at −0.7 V). The particle-size effect of Au trisoctahedron has also been investigated, showing that the FE for CO decreases almost linearly to 62.13% when the particle diameter increases to 100 nm. The X-ray diffraction characterizations together with the computational hydrogen electrode (CHE) analyses reveal that the (2 2 1) facets on Au trisoctahedron are more feasible than the (1 1 1) facets on Au colloids in stabilizing the critical intermediate COOH*, which are responsible for the higher FE and lower overpotential observed on Au trisoctahedron.

The stability of La2xSr1-2xTi1-xNixO3-δ (LSTN) and La7x/4Sr1-7x/4Ti1-xNixO3-δ (25LSTN) materials in high temperature reducing conditions has been studied with a special focus on the Ni exsolution process for SOFC anode / SOEC cathode application. In a general way, LSTN and 25LSTN compounds are stable after treatments at 800 °C in air and wet reducing atmosphere. The low chemical expansion makes them compatible with a use in an electrochemical Solid Oxide Cell. Those materials are therefore useful for an application as symmetric oxide cell electrode or only hydrogen electrode. In situ Nickel exsolution is evidenced at 800 °C in Ar/H2(2%) but is limited by a slow kinetics and a higher temperature pre-reduction is preferred before a use as SOFC anode (SOEC cathode). Depending on the treatment, in situ reduction or pre-reduction (T>1000 °C), the compounds are not in the same thermodynamic equilibrium state.

Metallic sodium is a promising anode material due to its remarkably high theoretical capacity (1165 mA h g−1) and favorable redox voltage (−2.71 V versus the standard hydrogen electrode). However, unstable solid-electrolyte-interface (SEI) film and uncontrollable dendritic sodium formation induce low Coulombic efficiency, inferior cycling performance and even severe safety issues, dragging the sodium metal anode out of practical applications. Recently, the reviving of lithium metal and application of related characterization techniques bring a new era of the alkali metal anode. Carbonaceous materials have been employed as the interface engineering layer or the host of sodium metal. The advantageous of carbon nanostructure are including high mechanical strength, low weight, high conductivity, various nanoarchitecture, large surface area, easy functionalization, and sustainable. With these merits, sodium metal is guided and uniformly deposited into/through carbon nanostructures without dendrite formation as the stable sodium metal anode. In this review, we summarize the recent progress in the strategies of suppressing the dendritic sodium by carbon nanostructures, and comprehensively analysis the related dendrite depression mechanism. We expect that this work can provide important insights into scientific and practical application of sodium metal batteries.

Anode materials are key components of batteries that significantly impact their specific energy and power. Li metal is considered as the ultimate anode due to its high theoretical capacity (∼3860 mA h/g) and low redox potential (−3.04 V vs. standard hydrogen electrode). Specifically, rechargeable Li metal batteries (LMBs) with enabled safety promise to surpass the energy density of current Li-ion batteries. Unfortunately, the apparently inevitable growth of dendritic Li, electrolyte consumption, the severe volume changes and the connected potential safety risks of LMBs limit their practical application. Recent strategies based on manipulation of electrolyte chemistry, interface engineering, and structure modification of Li host have reportedly achieved improvement. At the moment, the trend is to move towards all-solid-state LMBs. However, there are serious challenges in terms of low ionic conductivity, poor interfacial contact, and sluggish kinetics. While there are excellent reviews available, this review emphasizes problems and provides additional insight in advanced strategies for stabilizing Li metal anodes in liquid, polymer, ceramic and composite electrolytes. New approaches and novel materials to overcome the above challenges are referred. This review aims at raising relevant questions and outlining future strategies for next-generation high-energy storage systems.

The current ON/OFF switching of a solid oxide electrolysis cell is treated as elementary step for power variation in a steam electrolyser system. If the cell voltage in the ON mode is adjusted to the thermal neutral voltage, heat generation remains zero in both modes, which largely facilitates the thermal management. To verify whether the cells withstand the switching, an electrolysis durability test with an electrolyte supported solid oxide cell was performed during one year at about 850 °C. The cell consisted of a 3YSZ electrolyte, CGO diffusion-barrier/adhesion layers, a lanthanum strontium cobaltite ferrite (LSCF) oxygen electrode, and a nickel/gadolinia-doped ceria (Ni/GDC) steam/hydrogen electrode. The test included two operation blocks with each 40,000 cycles of 2 min duration and a current density of −0.7 Acm−2 in the ON mode (−0.07 Acm−2 in OFF mode), as well as steady-state ON periods with 5800 h duration. Voltage degradation was 5 mV/1000 h (0.4%/1000 h) and the increase in the area specific resistance 7 mΩcm2/1000 h, without notable dependence on current cycling. Impedance spectroscopic results were in agreement with the only small switching transients seen in the cell voltage; moreover, they confirmed a dominating ohmic degradation together with minor contributions from gas conversion and reaction, respectively. No electrode delamination was detectable after scheduled test completion.

The origin of the potential difference between the potential of zero charge of a metal/water interface and the work function of the metal is a recurring issue because it is related to how water interacts with metal surface in the absence of surface charge. Recently ab initio molecular dynamics method has been used to model electrochemical interfaces to study interfacial potential and the structure of interface water. Here, we will first introduce the computational standard hydrogen electrode method, which allows for ab initio determination of electrode potentials that can be directly compared with experiment. Then, we will review the recent progress from ab initio molecular dynamics simulation in understanding the interaction between water and metal and its impact on interfacial potential. Finally, we will give our perspective for future development of ab initio computational electrochemistry.

Using first principles calculations and the computational hydrogen electrode (CHE) model, we present the first systematic study of CO2 electrocatalytic reduction (CO2ER) on recently synthesized peanut-shaped carbon nanotube (FP5N) as well as N-doped FP5N structures. We find FP5N to be metallic with the symmetry of D5h point group. In addition, nitrogen doping in FP5N significantly reduces the overpotential of CO2ER. In contrast to graphitic N that reduces CO2 into CO with an overpotential of 0.65 V, the pyrrolic N, octatomic N and pyridinic N in FP5N convert CO2 into CH3OH with even lower overpotentials of 0.52, 0.52 and 0.60 V, respectively. These values are comparable to those of industrial transition metal catalysts and show that N-doped peanut-shaped carbon nanotubes can outperform conventional N-doped carbon nanomaterials in CO2 reduction.

The anaerobic antimonate [Sb(V)] reduction with a solid-state electrode serving as the sole electron donor was demonstrated by employing a bioelectrochemical system. The highest Sb(V) reduction efficiency was observed at the biocathode potential of −0.7 V versus standard hydrogen electrode using a cathode potential range from −0.5 V to −1.1 V. The scanning electron microscopy and energy dispersive X-ray spectroscopy indicated that both amorphous and crystallized Sb2O3 were formed as products of Sb(V) reduction. The irreversible recovery of bioelectrochemical Sb(V), when the cathode potential deviated from the optimal potential, was explained through the alteration in microbial communities, which was further elucidated by the next-generation sequencing of 16S rRNA gene amplicons. Chryseobacterium koreense and Stenotrophomonas nitritireducens were the dominant species of microbial consortia at Sb(V)-reducing biocathodes. This study revealed a novel option for bioremediation of Sb at underground contaminated sites, where the delivery of organic electron donors is limited or ineffective.

The present study investigated the electrochemical degradation of perfluorooctanoic acid (PFOA) by macro-porous titanium suboxide (p-TiSO) anode in the presence of sulfate at pH-neutral condition (pH 6.9 ± 0.3). Based on initial PFOA concentration of 0.1 mmol L−1, current density of 10 mA cm−2 and electrolysis of 2 h, the removal efficiencies of PFOA were 97.1% and 90.8% for Na2SO4 electrolyte (kapp = 2.1 h−1) and NaNO3 electrolyte (k = 0.84 h−1), corresponding to defluorination efficiency of 61.4% and 54.2%, respectively. The 2.3-fold enhancement of oxidation rate should be originated from the production of sulfate radicals (SO4 −) by activation of sulfate via direct electron transfer with anode and indirect OH-mediated oxidation under the potential of 3.01–3.41 V versus standard hydrogen electrode (SHE). The production of OH and SO4 − could be verified on a qualitative basis by using electron spin resonance (ESR) technology. Localized pH measurement achieved with a Pt/IrOx ultra-micro electrode revealed significantly lower pH inside the pores of p-TiSO anode (pH 2.6) compared to that in bulk electrolyte (pH 6.1). The formation of pH gradient should be attributed to surface interaction and diffusion restriction in the porous structure, and the resulting low pH was favorable for enhancing oxidizability of OH toward activation of bisulfate and oxidation of PFOA pollutant. This study offers a proof-in-concept demonstration of electrochemical activation of sulfate and PFOA degradation without need for chemical addition and pH adjustment, which can be realized by simply creating macro-porous structure of anode materials in electrochemical advanced oxidation process.

Self-doped TiO2 nanotube arrays (DNTA) were prepared for the electrooxidation of resistant organics. The anatase TiO2 NTAs had an improved carrier density and conductivity from Ti3+ doping, and the oxygen-evolution potential remained at a high value of 2.48 V versus the standard hydrogen electrode, and thus, achieved a highly enhanced removal efficiency of phenol. The second anodization could stabilize Ti3+ and improve the performance by removing surface TiO2 particles. Improper preparation parameters (i.e., a short anodization time, a high calcination temperature and cathodization current density) harmed the electrooxidation activity. Although boron-doped diamond (BDD) anodes performed best in removing phenol, DNTA exhibited a higher mineralization of phenol than Pt/Ti and BDD at 120 min because intermediates were oxidized once they are produced with DNTA. Mechanism investigations using reagents such as tert-butanol, oxalic acid, terephthalic acid, and coumarin showed that the DNTA mineralization resulted mainly from surface-bound OH, and the DNTA produced more than twice the amount of OH compared with BDD. The free OH on the BDD electrode was more conducive to initial substrate oxidation, whereas the adsorbed OH on the DNTA electrode mineralized the organics in situ. The preferential removal of p-substituted phenols on DNTA was attributed mainly to their electromigration and the aromatic intermediates that are hydrophobic were beneficial to mineralization.

Potassium-ion batteries (PIBs) have been identified as the possible alternatives to lithium-ion batteries (LIBs) due to the abundant reserve, low price, and low potential of potassium (−2.936 V vs. standard hydrogen electrode). However, there is still a challenge to achieve high energy density and long cycle life to promote its practical application. A simple synthesis strategy is reported in this paper to make the submicron metallic tin (Sn) particles encapsulated in the reduced graphene oxide (RGO) network, which is used as the electrode materials for PIBs. Sn-based particles are homogeneously distributed in the RGO network, abundant structural defects and a high Brunauer–Emmett–Teller (BET) surface area (136.5 m2/g), which enhance potassium ion storage of Sn@RGO anode. The Sn@RGO anode exhibits exhibiting a high charge capacity of 200 mAh g−1 after 50 cycles at 100 mA g−1 and an excellent rate capability of 67.1 mAh g−1 at 2000 mA g−1, while the pure Sn anode holds limited capacity and rate capability. Cyclic voltammogram measurements are conducted to verify the contributions of surface-dominated K-storage, demonstrating the high surface area having crucial effect on the capacity improvement. Meanwhile, the alloying phases are observed by in ex-situ XRD analysis at the fully depotassiation state. Consequently, this work shows a promising development of Sn-based anode materials with superior cost-effectiveness and sustainability for PIBs.

Polyhedral copper nanoparticles are prepared by a hydrothermal method, followed by galvanic replacement with platinum precursor in ethylene glycol to prepare bimetallic Cu@Pt electrocatalysts. The as-prepared bimetallic Cu@Pt catalyst are characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and inductive coupled plasma atomic emission spectrometer. The electrochemical properties of the resulted Cu@Pt electrocatalysts with different compositions are investigated for methanol oxidation reaction and oxygen reduction reaction. The bimetallic Cu@Pt electrocatalysts with low platinum loading demonstrate high Pt utilization efficiency in fuel cell reactions. The methanol oxidation reaction mass activity for Cu@Pt-8 catalyst is 791 A g−1, 5.1 times higher than that of the commercial Pt/C. The highest oxygen reduction reaction mass activity is found for Cu@Pt-25 (93 A g−1 at 0.9 V versus relative hydrogen electrode), which represents 61% enhancement relative to that of a commercial Pt/C (54 A g−1). It is believed that the superior performance of the as-prepared bimetallic Cu@Pt catalyst is mostly attributed to the improved Pt utilization and facilitated mass transport originating from the porous structure.

Electron transfer from solid electrodes to microbes through reversed extracellular electron transfer (EET) has been realized in bioelectrochemical systems (BESs), which have gained much attention in the realm of bioenergy and bioremediation. In this study, Shewanella oneidensis MR-1 was found to catalyze cathodic hydrogen evolution (HEv) at a potential of −0.758 V vs. standard hydrogen electrode (SHE) in a BES. Analysis via differential pulse voltammetry analysis revealed a strong enhancement of HEv by added nicotinamide adenine dinucleotide (NAD) but no impact by the addition of either NADH or riboflavin (RF) and flavin mononucleotide (FMN). Moreover, NADH, when added in combination with flavins inhibited cathodic EET and HEv. The mechanism by which these stimulations and inhibitions are not clear at this time. In summary, this study lays the foundation for understanding both reversed EET and hydrogen evolution catalyzed by S. oneidensis MR-1.

We report a successful fabrication of low-cost, high-efficient, structurally-rigid, porous WO3 photoelectrochemical (PEC) catalysts using polystyrene as the template by a sol-gel method and a high-temperature annealing treatment. The scanning electron microscopy and Brunauer-Emmett-Teller surface analysis results indicate that such WO3 monoliths possess a porous structure and a large specific surface area, which can supply lots of photogenerated charge transfer pathways as well as more surface PEC active sites. Compared with a commercially available WO3, our highly porous WO3 PEC catalysts show an excellent PEC water splitting activity. Particularly, the porous WO3 photoanodes calcinated in the presence of oxygen atmosphere at 450 °C for 7 h show the best PEC performance exhibiting the photocurrent density of 0.97 mA/cm2 at 1.23 V versus reversible the hydrogen electrode and the incident photon-to-current conversion efficiency up to 48.9% at 420 nm in 0.5 M Na2SO4 electrolyte under AM 1.5 G irradiation. Such excellent PEC performance is due to the high porosity of the WO3, promoting the fast transfer and the separation rate of photogenerated carriers during the PEC water splitting process.

Lithium metal is considered one of the most promising anode materials for realizing high volumetric and gravimetric energy density, owing to the high specific capacity (∼3860 mAh g−1) and the low electrochemical potential of lithium (−3.04 V vs. the standard hydrogen electrode). However, undesirable dendritic lithium growth and corresponding instability of the solid electrolyte interphase prevent safe and long-term use of lithium metal anodes. This paper presents a simple electrolyte approach to enhance the performance of lithium metal batteries by tuning the dielectric constant of the liquid electrolyte. Electrolyte formulations are designed by changing the concentration of ethylene carbonate to have various dielectric constants. This study confirms that high ethylene carbonate content in a liquid electrolyte enhances the cycling performance of lithium metal batteries because the electric field intensity applied to the electrolyte is reduced in relation to the polarization of the electrolyte and thus allows smooth lithium plating and formation of a stable solid electrolyte interphase. We believe that this approach provides an important concept for electrolyte system design suitable to lithium metal batteries.

Highly porous (specific surface area, SBET, 1400 m2/g) and rich in surface groups activated carbons (ACs) were obtained from cotton stalks using either a direct or indirect activation. They were characterized by adsorption of nitrogen, thermal analysis combined with mass spectrometry, potentiometric titration, and X-ray photoelectron spectroscopy (XPS). XPS analysis indicated that the indirect activation led to more nitrogen on the surface incorporated as pyridinic and graphitic/quaternary species. These species were beneficial for a carbon application as oxygen reduction reaction (ORR) electrocatalysts and supercapacitors. The carbons were catalytically active in ORR with a number of electron transfer from 2.15 to 3.40 and onset potential of 0.810 V vs. reference hydrogen electrode (RHE). Their capacitance was around 180 F g−1 at 1 A g−1 when measured in an alkaline medium. The dependence of the performance on the porosity and nitrogen content was found, indicating suitability of cotton stalks obtained using the indirect activation as precursors of carbons of promising electrochemically active features.

Bioelectrochemical system with biocatalyzed cathode is regarded as a promising approach for the enhanced bio-dechlorination of chlorinated aliphatic hydrocarbons (CAHs). However, the microbial community structure variation law and the corresponding function in the cathodic biofilm in response to the different cathode potentials remain poorly understood. In this study, biocathode systems were established for trichloroethene dechlorination under four cathode potentials (−0.06, −0.26, −0.46 and −0.66 V vs standard hydrogen electrode). About 2.6–4.3 times higher dechlorination rates were obtained in biocathodes than opened circuit, verifying the efficient electrostimulated bio-dechlorination. The highest trichloroethene dechlorination rate (1.01 mmol/L·d) was observed at −0.26 V, while higher (−0.06 V) or lower potentials (−0.46/−0.66 V) resulted in the 7.2–48.9% lower dechlorination rates. Under the different cathode potentials, the similar TCE dechlorination pathway was observed with cis-1,2-dichloroethene and ethene as the major and minor dechlorination products, respectively. The correlation and sharing network analysis of bacterial community illustrated that the negative potentials facilitated the enrichment of cathode-utilizing and dechlorination populations. The highest abundance of electroactive and dechlorinating bacteria (Lactococcus, Bacillus and Pseudomonas) and the highest expression of reductive dehalogenase (pceA and tceA) were observed at −0.26 V. The expression of extracellular electron transfer related gene omcX was promoted as the potential decreased. The decreased dechlorination capacity at potentials of −0.46 and −0.66 V could possibly be attributed to the lack of H2-utilizing dechlorinators and the low expressed pceA. This study offers insights into the molecular mechanism involved in the electrostimulated bio-dechlorination of CAHs by potential regulation.

The development of the hydrogen electrode is vital for the application of alkaline polymer electrolyte fuel cells (APEFCs). In this study, a series of Ni(OH)2 decorated Ni/C catalysts (Ni(OH)2-Ni/C) were prepared by a three-step electrochemical treatment of Ni/C. The existence of Ni(OH)2 was demonstrated by X-ray photoelectron spectroscopy (XPS), and the surface molar ratio of Ni(OH)2/Ni of the samples was estimated via an electrochemical method. The HOR catalytic activity of the catalysts was evaluated by a rotation disk electrode (RDE) method, and a “volcano plot” was established between the HOR exchange current (j0) and the surface molar ratio of Ni(OH)2/Ni. On top of the “volcano”, the surface molar ratio of Ni(OH)2/Ni is 1.1:1, the j0 of which was 6.8 times of that of Ni/C. The stability of the samples toward HOR was evaluated to be good. Our study added a systematic experimental evidence to the HOR research, showing that the HOR catalytic activity of Ni can be deliberately controlled via decoration of Ni(OH)2, which may help understanding the HOR mechanism on Ni.

Lithium metal batteries (LMBs) have attracted increasing attentions for their ultrahigh specific capacity (3860 mAh g−1) and the lowest electrode potential (−3.04 V vs. standard hydrogen electrode). However, the dynamic volume changes, the complex interfacial reactions, and the dendrite growth remain as the grand challenges in LMBs that prevent their practical applications. A bi-layer artificial solid electrolyte interphase (BL-SEI), which is composed of covalent graphitic materials (graphene and h-BN) and inorganic components (LiF, Li2O, Li3N, and Li2CO3), is rationally designed through comprehensive first-principles calculation to render a stable Li metal anode. Key interfacial properties, such as chemical stability, ionic conductivity, and mechanical strength, are systematically investigated to achieve a rational design of the BL-SEI. Among all the considered BL-SEI, the graphene/LiF combination is hopeful to exhibit the best interfacial stability and electrochemical performance. The protective role of BL-SEI for Li metal anode comes from the coupled effects through the anisotropic character and the defective structure. This work reveals the origin of the significant role of BL-SEI for achieving a stable Li metal anode from the atomic and electronic level, affording a paradigm for rational deign of a high-performance artificial SEI in working LMBs.

Aluminium finishing industry requires a stripping solution for anodic coatings for determination of their weight. The commonly applied one contains orthophosphoric acid as etchant and chromium trioxide as the corrosion inhibitor of metallic substrate. The latter, due to its toxicity, should be replaced, potentially with sodium molybdate. When sodium molybdate is dissolved in orthophosphoric acid, molybdophosphoric acid is formed. In this work the kinetics of dissolution of anodic coating was studied in 0.5 M H3PO4. Moreover, the influence of the initial concentration of Na2MoO4 in this solution was established. It was shown that molybdophosphoric acid species adsorb onto the surface and within the pores of anodic coating and decrease its dissolution rate in acidic solution. The mechanism of this process was evaluated by using Electrochemical Impedance Spectroscopy. Analysis of the impedance spectra revealed that adsorbed molybdophosphoric acid species increase the capacitance of the porous part of the coating from 0.7 to 1.1 μF and the resistance of its barrier layer from 0.3 MΩ to 2 MΩ in the solutions containing 0 and 25 mM of Na2MoO4 respectively. The corrosion potential of the specimens also increased from −400 mV vs. Standard Hydrogen Electrode to −200 mV in the solutions containing >25 mM of Na2MoO4.

Lithium (Li) metal has been proposed as the most promising anode for secondary lithium batteries with high energy density due to its considerable theoretical capacity (3860 mAh g−1) and lowest electrochemical potential (-3.04 V vs standard hydrogen electrode). However, the uncontrollable dendrite Li issues over repeated plating/stripping process results in huge volume change, low Coulombic efficiencies (CEs), and poor cycling performance. Here, a solid electrolyte interphase (SEI) layer mainly consisting of biphasic hybrid Li3Sb and LiF has been successfully in situ constructed on Li surface by spontaneous chemical reaction between Li and SbF3. The modified SEI can induce Li ions depositing on the linked-particle layer resulting from the relative low lithium diffusion coefficient of SEI layer component. The Li/Li symmetric cells with SbF3-modified Li (SF-Li) anodes show stable cycling over 400 h at 3.0 mA cm−2 for 3.0 mAh cm−2. The Li-S batteries with SF-Li anodes and ether-based electrolyte can achieve steady long-term cycling performance and high CEs. Particularly, the high voltage LiCoO2 (LCO)/Li batteries with SF-Li anodes and carbonate-based electrolyte also deliver excellent electrochemical properties even at harsh conditions. This work offers a new strategy to regulate Li ion deposition and benefits for the further development of safe Li metal batteries (LMBs).

To overcome the limitation of mass transfer and reaction rate involved in the biodegradation of gaseous o-xylene, the airlift reactor and microbial electrolysis cell were integrated to construct an airlift microbial electrolysis cell (AL-MEC) system for the first time, in which the bioanode was modified by polypyrrole to further improve biofilm attachment. The developed AL-MEC system achieved 95.4% o-xylene removal efficiency at optimized conditions, and maintained around 75% removal efficiency even while the inlet o-xylene load was as high as 684 g m−3 h−1. The existence of O2 exhibited a competition in electrons with the bioanode but a positive effect on ring-opening process in the o-xylene oxidation. The limitation of mass transfer had been overcome as the empty bed resistance time in the range of 20–80 s did not influence the system performance significantly. The microbial community analysis confirmed the o-xylene degradation microbes and electroactive bacteria were the dominant, which could be further enriched at 0.3 V against standard hydrogen electrode. This work revealed the feasibility of the AL-MEC system for the degradation of o-xylene and similar compounds, and provided insights into bioelectrochemical system design with high gaseous pollution removal capacity.

The production of an inexpensive, highly active electrocatalyst for a simple oxygen evolution reaction (OER) based on earth-abundant transition metals is still a major challenge. In addition, the ambiguity of the water splitting reaction (hydrogen evolution and OER) is a hurdle in the manufacture of suitable catalysts for the efficient water electrolysis process. Here, the synthesis of iron oxide/iron phosphide (Fe2O3/FeP) heterostructure and its counterparts Fe2O3 and FeP as cheap electrocatalysts for water electrolysis is presented. Characterization techniques such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy were used to analyze the structure of these electrocatalysts. Heterostructure Fe2O3/FeP has been shown to be a more active electrocatalyst than its counterparts. It initiates OER at a remarkably low potential of 1.49 V vs. reverse hydrogen electrode (RHE). For this electrocatalyst, a current density of 10 mA/cm2 is achieved at an overpotential of 264 mV for OER in 1.0 M potassium hydroxide solution and the value of the Tafel slope is 47 mV dec−1, outperforming its complements (Fe2O3 and FeP) under similar conditions. The results obtained are superior to those of previously reported Fe-based OER electrocatalysts. The Fe2O3/FeP electrocatalyst has proven its long-term stability by driving OER at 1.65 V (vs. RHE) for about 12.5 h.

Inorganic membranes hold great potential for various mainstream applications such as in wastewater treatment, drug manufacturing, food and beverage production, and dairy purification. There are numerous commercially available ceramic membranes which possess high corrosion resistance, high strength, and good heat resistance. However, these membranes are still prone to fouling causing a considerable decline in membrane performance and hence shorter life-times. Conventional methods for flux recovery include rigorous chemical backwashing, producing large amounts of sludge leading to disposal problems. In this work, commercial α-Alumina (Al2O3) ultrafiltration (UF) membranes were coated with titanium through an e-beam deposition process. The titanium coating rendered the membrane conductive, without changing the superhydrophilicity and average pore size of the membrane. Thermal degradation profiles suggested good thermal characteristics of the membrane. Good electrocatalytic activity for hydrogen evolution reaction was observed for the membrane, with an over-potential of 450 mV and 400 mV vs. Reference Hydrogen Electrode in acid and base solutions. The conductive membrane allowed for periodic electrolysis which is a fast and simple technique for fouling control and prevention. The membrane was used as a cathode during a cross-flow filtration setup, where 2.0 V was applied for 5 min during intervals. Without electrolysis, a considerable decline in flux was observed reaching almost 10% and 40% of its original value during yeast and sodium alginate (SA) filtration respectively. However, substantial flux recovery to 87% and 97.5 % was achieved after the first cleaning cycle during yeast and sodium alginate (SA) filtration respectively. Thereafter, considerable flux recovery was achieved during each subsequent electrolysis cycle. Membrane’s good electrocatalytic properties led to the generation of hydrogen bubbles which helped in sweeping away the foulants from the membrane’s surface.

In this work, photoelectrochemical properties of Cd-substituted tetrahedrite Cu10Cd2Sb4S13 (TH-Cd) monograin powders (MGPs) synthesized from Cu2S, CdS and Sb2S3 in two different molten salt (CdI2 and LiI) environments were studied in 0.1 M H2SO4 solution. Both materials exhibited a cathodic photocurrent that confirms the p-type conductivity. TH-Cd MGP grown in LiI was more stable and exhibited higher photocurrent (3.9 × 10−5 A/cm2) compared to the powder grown in CdI2 (3.3 × 10−6 A/cm2). Mott–Schottky method was used to calculate the acceptor concentrations; NA in TH-Cd grown in CdI2 was 2.6 × 1016 cm−3 and grown in LiI was 3.5 × 1015 cm−3. The valence band positions of TH-Cd MGPs were derived from the electrochemical impedance measurements. Valence band maxima found experimentally are at 0.49 eV for TH-Cd grown in CdI2 and 0.76 eV for TH-Cd grown in LiI, relative to normal hydrogen electrode.

The Li metal anode is an ideal candidate for next-generation batteries due to its ultra-high specific capacity (3860 mAh g−1) and low electrochemical potential (−3.040 V vs. standard hydrogen electrode). However, the large volume fluctuations, side reactions, and dendrite growth are serious problems that need to be solved before Li metal batteries (LMBs) can be commercialized. Herein, we develop a lithiophilic 3D Cu nanowire (3D CuNW) host that can enable molten Li infusion into the structure. Interestingly, the 3D host undergoes a structural transformation upon contact with molten Li and forms Cu-Li alloy crystallites on the surface, leading to the development of an ultra-high performance Li metal anode (3D Li@CuLi). The symmetrical cell performance of the 3D Li@CuLi electrode is found to be among the best reported for carbonate-based electrolytes and can achieve greater than 200 cycles at an ultra-high current density of 10 mA cm−2. Furthermore, full cells coupled with LiFePO4 cathodes show excellent cycling stability at a C-rate of 2 C for over 400 cycles with negligible capacity fade. This work provides a scalable and highly effective approach towards the fabrication of high performance 3D hosts with pre-stored Li metal for next-generation battery systems.