The widely used Li-ion batteries are insufficient for the rapid needs of high energy storage devices. Li−O2 batteries are regarded as a promising candidate to meet the needs in the future. This technology has attracted tremendous attention and led to remarkable scientific advances. We consider aprotic Li−O2 batteries in this review because they have drawn most attention of scientific research. However, various challenges should be resolved, such as low rate capability, poor cyclability, and instability, before realizing this technology in practice. The mass transfer of O2 and Li+ is a critical factor that affects the electrochemical performance of Li−O2 batteries. In this review, we discuss the effects of aprotic electrolytes, porous structure and operating conditions on the mass transfer, particularly the O2 mass transfer. Fundamental advances in developing materials (e.g. organic electrolytes) and practical optimizations of the electrode structure and operating conditions are key to enhance mass transfer of O2 and Li+. It is worthwhile continuing paying research effort due to the benefits of Li−O2 batteries. The research directions should be clarified to achieve breakthroughs in the future.

Alumina as dielectric material is commonly prepared via anodizing high purity etched foils in electrolyte, which vitally determines the performance of aluminum electrolytic capacitor. However, the traditional direct-current (DC) anodizing is limited due to a large amount of Joule heat production, space charge layer and unnecessary side reactions, which results in a great energy consumption and poor quality of oxide film. In this work, the symmetric pulsed-current (SPC) anodizing is introduced into the anodization of aluminum foil for electrolytic capacitor. SPC anodizing can contribute to the diffusion of heat during non-anodization period because of its pulse mode, lowering the thermally induced dissolution of alumina reacted with water. In addition, SPC anodizing can suppress the formation of space charge layer by alternating electric field so as to extract impurities out of the oxide film and lower energy consumption. Moreover, the SPC samples own the denser barrier-type alumina, which have better crystallinity resulting in the higher permittivity. Voltage-current output and side reactions during the anodizing process have been analyzed, demonstrating the less energy consumption and higher production efficiency of SPC method. In comparison of the DC anodized samples, the specific capacitance of SPC samples are elevated by 10.84%, and the energy consumption of SPC method is decreased by 25.5% in total. Therefore, SPC anodizing method has a good prospect for industrialization of aluminum electrolytic capacitor.

Hydrogen fuel cell technology has the potential for integration with renewable energy sources to produce electricity without the need for fossil fuels. Efforts are being made in producing cheap and effective electrodes from new materials to make hydrogen production more efficient. Gas evolution, in all cases, requires an accurate analysis of electrochemical behaviour of electrodes to quantify efficiency, improvement or stability. Knowing the exact gas volume by any method in real-time during electrochemical water splitting is urgently needed. Taking inspiration from the existing Broadband Acoustic Resonance Dissolution Spectroscopy technique, we demonstrate a new approach to continuously track the electrochemical water splitting via the gas volume evolution from hydrogen evolution reactions (HER) and oxygen evolution reactions (OER) processes. The technique may be used to unravel the true features of new electrode materials that evolve hydrogen, and correlate material electrochemistry to the true gas volume evolved in real-time.

Inverted-type polymer solar cells with poly[naphtho[1,2-c:5,6-c']bis[1,2,5]thiadiazole-5,10-diyl[3,4'-bis(2-butyloctyl)[2,2'-bithiophene]-5,5'-diyl]thiazolo[5,4-d]thiazole-2,5-diyl[3',4-bis (2-butyloctyl)[2,2'-bithiophene]-5,5'-diyl]] (PTzNTz) have attracted attention because of its high power conversion efficiency and thermal stability. However, the internal deterioration mechanism hasn’t yet been completely clarified. Here, we report operand electron spin resonance (ESR) spectroscopy of the highly durable PTzNTz polymer solar cells to investigate the mechanism of the device-performance deterioration at a molecular level. We identify the layer with accumulated charges in the PTzNTz cells by the analyses of light-induced components in the ESR spectra of the thin films and cells with PTzNTz. We observe the correlation between the increase in the number of spins and the decrease in the device performance. Notably, compared to the previously reported ESR studies of polymer solar cells, the PTzNTz solar cells have less charge accumulation and higher durability. This correlation holds even if another hole-transport layer of PTzNTz solar cells is utilized. The calculation with density functional theory is performed to analyze the charge-accumulation states in the cells. The present results are useful to develop further highly efficient and durable polymer solar cells.

Lithium (Li) metal has been considered as an important anode candidate to reach more powerful energy storage devices with higher gravimetric and volumetric capacities. Nevertheless, the growth of high surface area lithium (HSAL) and dendrites during the stripping / deposition of Li causes safety concern and low cycle life of Li metal batteries. Here we report the obtained results for protection of metallic lithium surface by using a gel polymer ionic liquid cross-linked by activation with UV radiation (UV-PIL). The UV-PIL protects Li against a constant degradation caused by the formation of unstable lithium metal-electrolyte interphase and cell dry out due to continuous electrolyte consumption. We observed retarded growth of dendrites when lithium metal is protected with UV-PIL and due to the lower ionic conductivity of UV-PIL some differences of mass transport are present compared to carbonate based liquid electrolyte. Nevertheless, the [email protected] negative electrode was successfully applied in a Li-ion battery with lithium iron phosphate (LFP) positive electrode, showing similar behavior compared to the bare Li surface.

The delafossite-type CuFeO2 (CFO) is a promising p-type thermoelectric oxide reported to show a large Seebeck coefficient, but the lack of a texturing method for CFO ceramics limits their thermoelectric performance. Here we show that textured CFO ceramics with an enhanced thermoelectric power factor can be obtained by a facile process based on the reactive templated grain growth (RTGG) method. Nanorods of α-FeOOH were synthesized by a hydrothermal reaction and used as templates for the RTGG process. Textured CFO ceramics with a high c-axis orientation were obtained by ordinal uniaxial pressing and subsequent reaction sintering of a mixed powder of the α-FeOOH nanorods and Cu2O particles. The best CFO ceramic with the highest orientation degree (Lotgering factor) of 0.71 was obtained at a sintering temperature of 1020 ℃. It was found that textured CFO ceramics are formed through a topotactic conversion process via an intermediate α-Fe2O3 phase. The textured CFO ceramic showed a high in-plane electrical conductivity, leading to an enhanced thermoelectric power factor of 1.4 × 10−4 W m−1 K−2 at 700 K, which is the highest value ever reported for undoped CFO ceramics.

We present a three terminal (3T) tandem approach for the interconnection of a perovskite top cell with an interdigitated back contact (IBC) silicon heterojunction (SHJ) bottom cell. The general viability of our cell design is further verified with drift diffusion simulations indicating efficient charge carrier transport throughout the whole device and an efficiency potential of ≈27% using readily available absorber and contact materials. Our experimental proof of concept device reaches a combined PCE of 17.1% when both subcells are operating at their individual maximum power point. To emulate different operation conditions, the current–voltage characteristics of both cells were obtained by measuring one subcell while the other cell was set to a fixed bias voltage. Only a slight mutual dependence of both subcells was found. As determined by electrical simulations, it likely stems from the resistance of the electron contact on the cell’s rear side, which is shared by both subcells. The optimisation of this contact turns out to be a major design criterion for IBC 3T tandems. We demonstrate that our current proof of concept cells are limited by this series resistance as well as by optical losses, and we discuss pathways to approach the simulated efficiency potential by an optimised device design.

Batteries based on Zn and other two-valent metals can be nearly ideal charge storage devices due to their high energy density combined with reliability, earth-abundance, and low flammability. Searching for high performance positive electrodes with good rate capability and adequate cycle life currently becomes a hot topic and a great challenge for developing Zinc batteries. Here, a binder free 3D porous graphene aerogel-supported α-MnO2 cathode (G-MnO2) is synthesized via a facile and scalable hydrogel method. The hybrid cathode of α-MnO2 nanotube attached on highly conductive interconnected graphene frameworks enables rechargeable Zn/G-MnO2 batteries with a high capacity of 321 mAhg-1 at 0.2C(1C=240 mAhg-1), good rate capability and ultralong cycle life (91% capacity retention over 300 cycles at a high current rate 3C). These findings open the pathway to a large family of low-cost high-performance Zn-battery and potentially other two-valent metals for a wide range of applications.

Cd-free Cu(In,Ga)(S,Se)2 (CIGSSe) solar cells are fabricated by all-dry process, where CIGSSe absorbers with and without alkali (K and Cs) treatments are used. Urbach energy (EU) is estimated in long-wavelength edge of external quantum efficiency. It is revealed that reduced EU through K and Cs treatments yields decreased open-circuit voltage deficit. Carrier recombination rates across devices are reduced through K and Cs treatments, corresponding to increased carrier lifetimes and decreased EU. Conversion efficiency of Cd-free CIGSSe solar cells with a structure of glass/Mo/CIGSSe/Zn0.8Mg0.2O/Zn0.9Mg0.1O:Al is enhanced from about 17.8% (none alkali) to 18.5% (with K) and to 20.3% (with Cs).

Herein, Ni element is for the first time put forward as a promising dopant to promote photoelectrochemical property of cuprous oxide (Cu2O) with particularly n-type conduction. An electrochemical route is utilized to deposit Ni:Cu2O on the indium tin oxide (ITO) coated glass as a dense thin film with treelike morphology, as revealed through scanning electron microscopy. Particularly, the incorporation of Ni that is verified via X-ray diffractometry leads to a compressive stress well compensating the tensile strain within Cu2O, which originates otherwise from large lattice mismatch between Cu2O and ITO. This in turn improves the crystallinity of the Ni:Cu2O thin film. More importantly, X-ray photoelectron spectroscopy indicates that the substitution of Ni(II) for Cu(I) boosts the carrier concentration to 8.41018 cm-3, as further evidenced by the Mott-Schottky analysis. Those enhancements along with advantageous band structure including a flat band potential of -1.1 V and a bandgap of ~2.1 eV that is alternatively derived from UV-Vis spectroscopy allow Ni:Cu2O delivering an outstanding photocurrent of 2.5 mAcm-2 (at 0.3 V vs. Ag/AgCl) for solar water splitting. Such performance well surpasses those of other reported n-type Cu2O photoanodes more than twofold, attesting the great promise of Ni:Cu2O in this work for solar-related applications.

An efficient metal-free formulation of a hole transport material (HTM) based on an ionic liquid polymer is developed for n-i-p perovskite solar cells (PSCs), to address reproducibility issues related to the use of complex dopant mixtures based on lithium salts and cobalt coordination complexes. The conductivity of the HTM is thus significantly improved by 4 orders of magnitude, up to 1.9 x 10-3 S.cm-1, using poly(1-butyl-3-vinylimidazolium bis(trifluoromethylsulfonyl)imide) (PVBI-TFSI) as dopant. Introduced in the FTO/c-TiO2/mp-TiO2/K0.05(MA0.15FA0.85)0.95PbI2.55Br0.45/HTM/Au PSC configuration, PVBI-TFSI-HTM formulation shows record power conversion efficiency as high as 20.3 %, versus 18.4 % for the standard lithium salt-HTM formula-tion, with considerably reduced hysteresis and improved reproducibility. Mechanistic investigations suggest that PVBI-TFSI acts as a source of protons promoting the HTM oxidation. To the best of our knowledge, this is the best PSC performance reported so far with an alternative organic p-dopant in perovskite solar cells.

The formation of c-Li3.75Si is known to be detrimental to silicon anodes in lithium-ion batteries. To suppress the formation of this crystalline phase and improve the electrochemical performance of Si-based anodes, three approaches were amalgamated: addition of a nickel adhesion sublayer, alloying of the silicon with titanium, and the addition of either carbon or TiO2 as a capping layer. The silicon-based films were analyzed by a suite of methods, including scanning electron microscopy (SEM) and a variety of electrochemical methods, as well as X-ray photoelectron spectroscopy (XPS) to provide insights into the composition of the resulting solid electrolyte interphase (SEI). A nickel adhesion layer decreased the extent of delamination of the silicon from the underlying copper substrate, compared to Si deposited directly on Cu, which resulted in less capacity loss. Alloying of silicon with titanium (85% silicon, 15% titanium) further increased the stability. Finally, capping these multilayer electrodes with either a thin 10 nm layer of carbon or TiO2 resulted in the best electrode behavior, and lowest cumulative relative irreversible capacity. TiO2 is slightly more effective in enhancing the capacity retention, most likely due to differences in the resulting solid electrolyte interphase (SEI). The combination of an adhesion layer, alloying, and surface coatings shows a cumulative suppression of the formation of c-Li3.75Si and SEI, resulting in the greatest improvement of capacity retention when all three are incorporated together. However, these strategies appear to only delay the onset of the c-Li3.75Si phase; eventually, the c-Li3.75Si phase will form, and at that point, the capacity degradation rate of all the electrodes becomes similar.

Developing advanced carbon nanomaterials with reasonable pore distribution and interconnection, matching the charge-storage capacities and electrode kinetics between capacitive electrode and battery-type electrode are two of the biggest challenges in lithium-ion capacitors (LICs). In this work, a sustainable strategy to fabricate N/S dual doped hierarchical porous carbon nanofibers (N/S-CNF) is developed via electrospinning and thiourea treatment, which was employed as both capacitor-type cathode and battery-type anode for LICs. With rational design, N/S-CNF can not only offer a large specific surface area with hierarchical pore structure but also be uniformly doped with heteroatoms, which is desirable for improving the electrochemical performance of both cathode and anode for LICs, and alleviating the mismatch between the two electrodes. LICs assembled with the designed N/S-CNF electrodes can deliver a high energy density of 154 Wh kg-1 with a stable capacitance retention of 92% after 6000 cycles. Our work is expected to open up new avenues for developing heteroatom-doped porous carbon nanomaterials applied in other energy conversion and storage devices.

Fuel flexibility is an attractive advantage of solid oxide fuel cell (SOFC) technology, however, carbon deposition issue with widely used Ni-cermet anodes in hydrocarbon fuels seriously limits its long-term stability. While alternative anode materials have been developed to overcome this issue, none of these materials demonstrates electronic conductivity and (electro) catalytic activity that can compete with those of Ni-cermets. Therefore, it is desired to use Ni-cermet anode while being able to effectively prevent carbon deposition. For this purpose, a microtubular alumina substrate-supported thin film SOFC Ni-Ce0.8Sm0.2O1.9/Ce0.8Sm0.2O1.9/PrBaCo2O5+δ (Ni-SDC/SDC/PBCO) is studied and compared with conventional Ni-SDC anode and NiAl2O4 substrate-supported cells. Alumina- and NiAl2O4-supported cells obtain peak power densities of 1.15/1.23 W cm-2 and 0.79/0.82 W cm-2 at 700 ℃ in wet hydrogen/dry methane, comparable to those of Ni-SDC-supported cell, i.e., 1.5/1.08 W cm-2 respectively. Both alumina- and NiAl2O4-supported cells demonstrate very good short-term stability with the former showing better stability in dry methane under both high current loading and open circuit voltage conditions, whereas Ni-SDC-supported cell quickly dies out. Carbon deposition and prevention mechanisms of three different cell designs are discussed by combining post-test cell characterizations with various chemical/electrochemical reactions.

Ag-based argyrodites with a general formula of Ag(12-n)Bn+X6 (B=Ga/Al/Si/Ge/Sn and X=S/Se/Te) have recently attracted much attention as promising thermoelectrics due to their ultra-low lattice thermal conductivity and richness in the composition. Most of these Ag-based argyrodites are n-type conduction semiconductors and show a promising thermoelectric figure of merit (zT). However, p-type argyrodites have much less been reported and this motivates the current work to focus on a novel p-type argyrodite Ag9GaTe6 for thermoelectric applications. Although various doping (Cd, Zn, Mg, Nb, Se and Cu) were found to insufficiently increase the hole concentration for a degenerate conduction, a peak zT of 0.65 at 600 K can still be realized in p-type Ag9Ga0.95Cd0.05Te6. This largely relies on a lattice thermal conductivity of only ~0.2 W/m-K (nearly independent with temperature and doping), which results from the low sound velocity, strong lattice anharmonicity and complex crystal structure. This work demonstrates the potential of Ag9GaTe6 as a promising p-type thermoelectric material, particularly with a further increase in hole concentration.

Li-O2 batteries are considered as one of the promising beyond Li-ion battery technologies owing to their high energy density. But poor cycle life due to sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) hinder the commercialization of this technology. Hence fabrication of highly efficient ORR and OER catalyst is of paramount importance in order to improve the cyclic stability and longevity of this device. Herein, we discuss systematically the synthesis and electrochemical analysis of such bifunctional perovskite catalysts: pristine CaMnO3 and its defect induced counterpart. When evaluated as cathode catalyst in Li-O2 battery along with a redox mediator LiI, the oxygen deficient CaMnO3 gives an improved cycle life reported at a high current rate of 500 mA g-1 with a capacity of 500 mA h g-1 in comparison with similar catalysts reported in literature. Introduction of defects in the pristine framework predominantly improves the catalytic activity by lowering the overpotential. The presence of oxygen vacancies creates mixed-valence states of Mn3+/Mn4+ which modify the electronic structure resulting in the improved catalytic activity. Comprehensive phase and compositional analysis confirm the formation of the desired defect induced structure with improved catalytic activity towards ORR and OER which is elaborated with electrochemical analysis.

Fifty atomic layer deposition (ALD) cycles of trimethylaluminum and water were applied to single-layer graphene on copper and graphene on Nafion® membranes that result in alumina coatings that fully block photoelectron emission from the underlying substrate materials (copper and Nafion® respectively). This finding is consistent with relatively uninhibited alumina ALD nucleation and growth to a thickness of ~5 nm and further suggests that the alumina layer is continuous with no uncoated regions exposed. The ALD-derived alumina coatings are good barriers to large ions, e.g. from aqueous ferric chloride, but they have a relatively modest effect on proton transmission through graphene as measured in electrochemical hydrogen pump cell experiments. Proton currents of approximately 0.5 A cm-2 were obtained through Nafion® / graphene / ALD alumina / Nafion® at a modest bias voltage of 150 mV, which reflects a diminishment by less than half relative to the value for membranes without the 50 cycles of ALD alumina applied to the graphene. Proton transmission through the ALD alumina layer is thought to occur via hydrated alumina surfaces within the relatively porous ALD alumina layer on the graphene surface, and perhaps also at grain boundaries formed in the alumina during the ALD process.

MXenes are a recently discovered family of two-dimensional transition metal carbides, nitrides and carbonitrides with electronic properties that can be tuned by their chemistry and structure. Herein we have applied THz spectroscopy to investigate the microscopic conductivity and photoexcited charge carrier dynamics in two Mo-based MXenes: Mo2Ti2C3Tz and Mo2TiC2Tz. We find that both have high intrinsic carrier densities (~ 1020 cm-3 in Mo2Ti2C3Tz and ~ 1019 cm-3 in Mo2TiC2Tz) and mobilities, and exhibit high conductivities within individual nanosheets. Optical excitation results in a transient conductivity increase in both Mo-based MXenes, in stark contrast with the most studied member of MXene family, Ti3C2Tz, where photoexcitation suppresses conductivity for nanoseconds. De-intercalation of water and other species from van der Waals gaps between the nanosheets by mild vacuum annealing further improves the long-range, inter-nanosheet transport of the photoexcited carriers and increases their lifetime. High and long-lived photoinduced conductivity that can be engineered by substituting Mo for Ti render Mo-based MXenes attractive for a variety of optoelectronic, sensing and photoelectrochemical applications.

Metal-nitrogen-carbon (M-N-C) molecular catalysts within NiN4 active structure have been extensively studied as selective and active catalysts towards electrochemical reduction of CO2 to CO. The key challenge for a practical M-N-C catalyst is to increase the density of atomic metal active sites that achieves the partial current density of CO (jCO) relevant to the industrial level at lower overpotentials. Here, we revealed the effect of physical and chemical properties of carbon substrates and synthetic process on the tuning of the density of atomic metal active sites as well as the role of reaction chemistry in enhancing the jCO and reducing the overpotential. The achievable loading of NiN4 active site in the Ni-N-C is determined by the combined content of pyridinic and pyrrolic N functionalities and Ni-N coordination efficiency derived from the pyrolytic step rather than the uptake capability of Ni2+ in the adsorption step in the case of carbon black with high specific surface area (>1000 m2/g). The N dopant content can be improved by modifying oxygen functional groups on the surface of carbon black, optimizing the pyrolytic temperature and iterating the doping step. Through a combination of all optimum factors, the resultant Ni-N-C catalyst has a maximum loading of ~4.4wt.% for atomic Ni. This Ni-N-C catalyst exhibited Faradaic efficiency (FE) of CO of 97% and jCO of -152 mA cm-2 at -0.93 V vs. RHE in a flow cell using 0.5 M KHCO3 electrolyte while showing 93% FE of CO and jCO of -67 mA cm-2 at -0.61 V vs. RHE at 1 M KOH. Adding KI to the base electrolyte significantly magnified the jCO to larger than -200 mA cm-2 at a potential of -0.51 V vs. RHE while maintaining the almost unity FE of CO. The Ni-N-C is compatible with the membrane electrode assembly based electrolyzor in which the jCO also achieved > 200 mA cm-2 at cell voltage of around 2.7 V.

The development of oxygen reduction reaction (ORR) electrocatalysts comprising abundant elements is highly desirable for achieving widespread use of fuel cells. Optimal ORR catalysts should have moderate binding strength (ΔEads) with O2-derived intermediates, where the metal species and its coordination numbers are the essential determining factors for ΔEads. However, in conventional non-noble-metal-based ORR catalysts, such as metal–nitrogen-doped carbons, the metal species and its coordination structure cannot freely be chosen. In contrast, covalent organic frameworks (COFs), which are cross-linked microporous polymers, have high design flexibility; as such, they can be purposefully designed using a wide range of monomers. The present work investigated the adsorption strength of ORR intermediates on single 3d metal atoms (Mn, Fe, Co, Ni, and Cu) doped in COFs with different coordination structures using first principles calculations toward the development of efficient non-noble metal ORR catalysts. The adsorption strength of the intermediates was found to monotonically increase as either the number of d-electrons or coordination number of metal centers decreased, and a volcano-type relationship was observed between the adsorption energies of the intermediates and the theoretical ORR activities. Therefore, to develop efficient non-noble-metal-based ORR electrocatalysts, the adsorption strength should be tuned close to the volcano peak by an appropriate choice of metal species and/or coordination number as the control parameters. Considering the high designability of metal species and of its coordination numbers in COFs, COFs are expected to become the next-generation platform of supports of single-atom catalysts using the design direction provided by the present work.

A cyclometalated Ir(III) diimine complex [Ir(NBI)2(phen)]PF6, NBI = 1,8-naphthalenebenzimidizole and phen = 1,10-phenanthroline, exhibits excellent photostability as a sensitizer in a 3-component homogeneous aqueous photocatalytic hydrogen producing system. Here, [Co(dmgH)2(py)Cl] serves as the hydrogen evolving catalyst and N,N-dimethyl-p-toluidine (DMT) serves as a sacrificial single electron donor. The [Ir(NBI)2(phen)]PF6 photosensitizer remained active over the course of 90 hours of visible-light-induced (λex = 452 nm, 540 mW) H2 production photocatalysis, yielding a turnover number (H2/photosensitizer) of 575 occurring near neutral pH conditions. The proton source was verified as being derived from aqueous protons by detecting the headspace gas composition through mass spectrometry in experiments using deuterated water. Mercury metal was used as a selective poisoning test, intended to sequester any metal-based nanomaterial(s) produced in side reactions, and provided evidence that the current photocatalytic system was indeed operating in a purely homogeneous manner. Stern-Volmer analyses revealed that reductive quenching by DMT was the dominant (reductive) quenching pathway immediately following light activation in the photocatalytic cycle. The electron transfer cage escape efficiency for this reaction was measured to be 78%, likely attributable to the significant triplet ligand-centered (3LC) character of the lowest excited state manifold. This enables the majority of the charged-separated species to enter the subsequent catalytic cycle, thereby enhancing H2 production. In the presence of the [Co(dmgH)2(py)Cl] hydrogen evolution catalyst, the one electron reduced species of the ground state Ir(III) complex transfers an electron to this catalyst with a rate constant of 2.5 × 109 M-1s-1, producing a Co(II) intermediate while regenerating the resting state of the photosensitizer. The combined experimental results suggest numerous benefits in homogeneous photocatalysis become realized when 3LC excited states become involved in excited state electron transfer chemistry and can likely be leveraged in future photocatalytic schemes.

Electrochemical splitting of water to hydrogen is widely considered as an efficient and sustainable solution to relive energy crisis. In this work, we report a facile dealloying method based on metallic glass (Ni61Zr36Mo3) to introduce abundant oxygen vacancies (Ov) for electrocatalytic hydrogen evolution reaction (HER). The corroded ribbons are composed of a sandwich-like structure with Ni-Mo-O nanoporous layer outside and raw metallic glass inside. This complex structure delivers low overpotential of 71±2.6 mV at -20 mA cm-2 in 1.0 M KOH solution, a Tafel slope of 57±3 mV dec-1, and 100 h long-term stability for HER, which is much better than those of crystallized counterpart, nanoporous Ni, and commercial benchmark 20% Pt/C electrocatalyst. The high concentration of oxygen vacancies (71.5%), the alloying effect of Mo, and amorphous composition synergistically contribute to the superior electrocatalytic ability and enhanced reaction kinetic of nanoporous Ni-Mo-O, indicating it an excellent low-cost alternative for platinum in hydrogen production.

Magnesium (Mg) batteries have attracted growing attention owing to their low cost and high volumetric capacity. Mg/S batteries are of particular interest because of the high capacities of Mg and sulfur, which cooperatively enable high energy densities. However, the shuttling polysulfides during the S0/S2− conversion impair the cathode stability and corrode the Mg anode. This work reports the in-situ sulfurization of carbon-confined cobalt in a mesoporous matrix ([email protected]) through sulfur melt impregnation and its effectiveness in uplifting the cathode stability and alleviating the Mg anode corrosion (i.e. formation of magnesium sulfides/sulfates). The CoSx species play important roles in binding with polysulfides and regulating the notorious polysulfide shuttle. Both the carbon matrix and the preserved cobalt are excellent electron conductors and allow fast charge transfer to the CoSx species, which become the active sites that facilitate the interaction with magnesium polysulfides and improve the cathode kinetics. These combined effects collectively give rise to the stable capacity of 280 mAh/g at 0.2 C (1 C = 1675 mA/g) for at least 400 cycles.