Efficient Hydrogen Evolution on Antiperovskite CuNCo3 Nanowires by Mo Incorporation and its Trifunctionality for Zn Air Batteries and Overall Water Splitting.

The current development of single electrocatalyst with multifunctional applications in overall water splitting (OWS) and zinc-air batteries (ZABs) is crucial for sustainable energy conversion and storage systems. However, exploring new and efficient low-cost trifunctional electrocatalysts is still a significant challenge. Herein, the antiperovskite CuNCo3 prototype, that is proved to be highly efficient in oxygen evolution reaction but severe hydrogen evolution reaction (HER) performance, is endowed with optimum HER catalytic properties by in situ-derived interfacial engineering via incorporation of molybdenum (Mo). The as-prepared Mo-CuNCo3 @CoN nanowires achieve a low HER overpotential of 58 mV@10 mA cm-2 , which is significantly higher than the pristine CuNCo3 . The assembled CuNCo3 -antiperovskite-based OWS not only entails a low overall voltage of 1.56 V@10 mA cm-2 , comparable to most recently reported metal-nitride-based OWS, but also exhibits excellent ZAB cyclic stability up to 310 h, specific capacity of 819.2 mAh g-1 , and maximum power density of 102 mW cm-2 . The as-designed antiperovskite-based ZAB could self-power the OWS system generating a high hydrogen rate, and creating opportunity for developing integrated portable multifunctional energy devices.

Room-Temperature Transient Hydrogen Uptake of MgH2 Induced by Nb-Doped TiO2 Solid-Solution Catalysts.

The practical applications of MgH2 as a high-density hydrogen carrier depend heavily on efficient and low-cost catalysts to accelerate the dehydriding/hydriding reactions at moderate temperatures. In the present work, this issue is addressed by synthesizing Nb-doped TiO2 solid-solution-type catalysts that dramatically improve the hydrogen sorption performances of MgH2. The catalyzed MgH2 can absorb 5 wt % of H2 even at room temperature for 20 s, release 6 wt % of H2 at 225 °C within 12 min, and the complete dehydrogenation can be achieved at 150 °C under a dynamic vacuum atmosphere. Density functional theory calculations reveal that Nb doping introduces Nb 4d orbitals with stronger interaction with H 1s into the density of states of TiO2. This considerably enhances both the adsorption and dissociation ability of the H2 molecule on the catalysts surface and the hydrogen diffusion across the specific Mg/Ti(Nb)O2 interface. The successful implementation of solid solution-type catalysts in MgH2 offers a demonstration and inspiration for the development of high-performance catalysts and solid-state hydrogen storage materials.

In Situ Formation of Li2SiO3-Li-NaCl Interface on Si and Its Effect on Hydrogen Evolution.

Silicon has emerged as a competitive candidate for hydrolytic hydrogen production due to its high theoretical hydrogen yield, low cost, and on-demand availability. However, the hydrolysis reaction is extremely restrained by passivated SiO2, including the original one on the Si surface and the generated one during hydrolysis, and almost no hydrogen is produced in pure water. Herein, the original SiO2 surface has been effectively removed by milling micro-Si mixed with a small amount of Li metal and NaCl. An artificial soluble interface on Si has been established containing Li2SiO3, Li, and NaCl. Once micro-Si is placed into water, fresh Si surface can be exposed and a weak LiOH solution can be generated due to the fast dissolution of the interface layer, resulting in the rapid liberation of hydrogen gas. Accordingly, the modified micro-Si displays a significantly enhanced hydrogen production in pure water at 30 °C (1213 mL g-1 H2 within 3.0 h), which is 2.0 and 4.7 times higher than that observed for ball-milled Si and raw Si in 0.06 M LiOH solution, respectively. In addition, it also exhibited an outstanding operation compatibility for practical uses. This work has proposed a green, effective, and scalable strategy to promote hydrogen production from the hydrolysis of Si-based systems.

Facile and Scalable Mechanochemical Synthesis of Defective MoS2 with Ru Single Atoms Toward High-Current-Density Hydrogen Evolution.

Designing a facile strategy to prepare catalysts with highly active sites are challenging for large-scale implementation of electrochemical hydrogen production. Herein, a straightforward and eco-friendly method by high-energy mechanochemical ball milling for mass production of atomic Ru dispersive in defective MoS2 catalysts (Ru1 @D-MoS2 ) is developed. It is found that single atomic Ru doping induces the generation of S vacancies, which can break the electronic neutrality around Ru atoms, leading to an asymmetrical distribution of electrons. It is also demonstrated that the Ru1 @D-MoS2 exhibits superb alkaline hydrogen evolution enhancement, possibly attributing to this electronic asymmetry. The overpotential required to deliver a current density of 10 mA cm-2 is as low as 107 mV, which is much lower than that of commercial MoS2 (C-MoS2 , 364 mV). Further density functional theory (DFT) calculations also support that the vacancy-coupled single Ru enables much higher electronic distribution asymmetry degree, which could regulate the adsorption energy of intermediates, favoring the water dissociation and the adsorption/desorption of H*. Besides, the long-term stability test under 500 mA cm-2 further confirms the robust performance of Ru1 @D-MoS2 . Our strategy provides a promising and practical way towards large-scale preparation of advanced HER catalysts for commercial applications.

Phenylphosphonic acid as a grain-refinement additive for a stable lithium metal anode.

Phenylphosphonic acid (PPOA) has been proposed as a new additive for carbonate electrolytes, in which the complexation reaction between PPOA and Li+ reduces the nucleus size and boosts the nucleation quantity during the plating process. Thus, enhanced cycling stability is obtained in both symmetric cells and full cells.

Hydrogen Production via Hydrolysis and Alcoholysis of Light Metal-Based Materials: A Review.

As an environmentally friendly and high-density energy carrier, hydrogen has been recognized as one of the ideal alternatives for fossil fuels. One of the major challenges faced by "hydrogen economy" is the development of efficient, low-cost, safe and selective hydrogen generation from chemical storage materials. In this review, we summarize the recent advances in hydrogen production via hydrolysis and alcoholysis of light-metal-based materials, such as borohydrides, Mg-based and Al-based materials, and the highly efficient regeneration of borohydrides. Unfortunately, most of these hydrolysable materials are still plagued by sluggish kinetics and low hydrogen yield. While a number of strategies including catalysis, alloying, solution modification, and ball milling have been developed to overcome these drawbacks, the high costs required for the "one-pass" utilization of hydrolysis/alcoholysis systems have ultimately made these techniques almost impossible for practical large-scale applications. Therefore, it is imperative to develop low-cost material systems based on abundant resources and effective recycling technologies of spent fuels for efficient transport, production and storage of hydrogen in a fuel cell-based hydrogen economy.

Breaking the Passivation: Sodium Borohydride Synthesis by Reacting Hydrated Borax with Aluminum.

A significant obstacle in the large-scale applications of sodium borohydride (NaBH4 ) for hydrogen storage is its high cost. Herein, we report a new method to synthesize NaBH4 by ball milling hydrated sodium tetraborate (Na2 B4 O7 ⋅ 10H2 O) with low-cost Al or Al88 Si12 , instead of Na, Mg or Ca. An effective strategy is developed to facilitate mass transfer during the reaction by introducing NaH to enable the formation of NaAlO2 instead of dense Al2 O3 on Al surface, and by using Si as a milling additive to prevent agglomeration and also break up passivation layers. Another advantage of this process is that hydrogen in Na2 B4 O7 ⋅ 10H2 O serves as a hydrogen source for NaBH4 generation. Considering the low cost of the starting materials and simplicity in operation, our studies demonstrate the potential of producing NaBH4 in a more economical way than the commercial process.

Excellent Cyclic and Rate Performances of SiO/C/Graphite Composites as Li-Ion Battery Anode.

The SiO-based composites containing different carbon structures were prepared from asphalt and graphite by the milling, spray drying, and pyrolysis. In the obtained near-spherical composite particles, the refined amorphous SiO plates, which are coated with an amorphous carbon layer, are aggregated with the binding of graphite sheets. The SiO/C/Graphite composites present a maximum initial charge capacity of 963 mAh g-1 at 100 mA g-1, excellent cyclic stability (~950 mAh g-1 over 100 cycles), and rate capability with the charge capacity of 670 mAh g-1 at 1,000 mA g-1. This significant improvement of electrochemical performances in comparison with pristine SiO or SiO/C composite is attributed to the unique microstructure, in which both the graphite sheets and amorphous carbon coating could enhance the conductivity of SiO and buffer the volume change of SiO. The higher pyrolysis temperature causes the denser spherical microstructure and better cycle life. Our work demonstrates the potential of this SiO/C/Graphite composite for high capacity anode of LIBs.

Kinetically Controllable Hydrogen Generation at Low Temperatures by the Alcoholysis of CaMg2 -Based Materials in Tailored Solutions.

The alcoholysis of CaMg2 -based materials for hydrogen generation is reported. Compared to hydrolysis in water, hydrogen supply from alcoholysis shows an excellent potential for outdoor applications, which not only bypasses the formation of passivation layers deposited on the surface of particles but also breaks the temperature bottleneck in which hydrolysis occurs over 0 °C. To remove the troublesome freezing issue of the water solution system in low-temperature conditions, here, instead of pure methanol, methanol/water and methanol/ethanol solutions are applied to react with CaMg2 alloy (CM2 ) and its hydrides (H-CM2 ) for hydrogen generation. Compared with pure water and ethanol, the reaction of CaMg2 -based materials with methanol possesses much faster reaction kinetics and gives a considerable hydrogen yield. CM2 can generate 858 mL H 2 g-1 within only 3 min at room temperature as it reacts vigorously with methanol, as opposed to a low hydrogen yield with ethanol and water (395 and 224 mL H 2 g-1 within 180 min, respectively) under the same conditions. Even at -20 °C, there is still over 600 mL H 2 g-1 released at a conversion rate of 70.7 % within 100 min for methanolysis, which shows its prominent advantage for hydrogen production, especially in winter or subzero areas. Interestingly, the methanolysis byproducts can transform into metal hydroxides and methanol in the reaction with water, and the methanol may be separated and reused as an intermediate. Moreover, the hydrogen behavior of CaMg2 methanolysis can be well controlled by tailoring the components of the solutions to deliver a promising hydrogen supply system for the hydrogen economy.

Closing the Loop for Hydrogen Storage: Facile Regeneration of NaBH4 from its Hydrolytic Product.

Sodium borohydride (NaBH4 ) is among the most studied hydrogen storage materials because it is able to deliver high-purity H2 at room temperature with controllable kinetics via hydrolysis; however, its regeneration from the hydrolytic product has been challenging. Now, a facile method is reported to regenerate NaBH4 with high yield and low costs. The hydrolytic product NaBO2 in aqueous solution reacts with CO2 , forming Na2 B4 O7 ⋅10 H2 O and Na2 CO3 , both of which are ball-milled with Mg under ambient conditions to form NaBH4 in high yield (close to 80 %). Compared with previous studies, this approach avoids expensive reducing agents such as MgH2 , bypasses the energy-intensive dehydration procedure to remove water from Na2 B4 O7 ⋅10 H2 O, and does not require high-pressure H2 gas, therefore leading to much reduced costs. This method is expected to effectively close the loop of NaBH4 regeneration and hydrolysis, enabling a wide deployment of NaBH4 for hydrogen storage.

B,N Codoped Graphitic Nanotubes Loaded with Co Nanoparticles as Superior Sulfur Host for Advanced Li-S Batteries.

Lithium-sulfur batteries (LSBs) are considered as one of the best candidates for novel rechargeable batteries due to their high energy densities and abundant required materials. However, the poor conductivity and large volume expansion of sulfur and the "shuttle effect" of lithium polysulfides (LPSs) have significantly hindered the development and successful commercialization of LSBs. Bean-like B,N codoped carbon nanotubes loaded with Co nanoparticles (Co@BNTs), which can act as advanced sulfur hosts for the novel LSB cathode, are fabricated. Uniform graphitic nanotubes improve the conductivity of the electrode and load more electroactive sulfur and buffer volume expansion during the electrochemical reaction. In addition, loaded Co nanoparticles and codoped B,N sites can significantly suppress the "shuttle effect" of LPSs with strong chemical interaction. It is established that the Co nanoparticles and codoped B,N can provide more active sites to catalyze the redox reaction of sulfur cathode. This stable Co@BNTs-S cathode displays an exceptional electrochemical performance (1160 mA h g-1 after 200 cycles at 0.1 C) and outstanding stable cycle performance (1008 mA h g-1 after 400 cycles at 1.0 C with an extremely low attenuation rate of 0.038% per cycle).

Low temperature dehydrogenation properties of ammonia borane within carbon nanotube arrays: a synergistic effect of nanoconfinement and alane.

Ammonia borane (AB, NH3BH3) is considered as one of the most promising hydrogen storage materials for proton exchange membrane fuel cells due to its high theoretical hydrogen capacity under moderate temperatures. Unfortunately, its on-board application is hampered by the sluggish kinetics, volatile byproducts and harsh conditions for reversibility. In this work, AB and AlH3 were simultaneously infiltrated into a carbon nanotube array (CMK-5) to combine the synergistic effect of alane with nanoconfinement for improving the dehydrogenation properties of AB. Results showed that the transformation from AB to DADB started at room temperature, which promoted AB to release 9.4 wt% H2 within 10 min at a low temperature of 95 °C. Moreover, the entire suppression of all harmful byproducts was observed.

Facile Synthesis of Peapod-Like Cu3 Ge/Ge@C as a High-Capacity and Long-Life Anode for Li-Ion Batteries.

As anode materials for high-performance Li-ion batteries, peapod-like Ge-based composites, including Ge, a Li-inactive conducting Cu3 Ge, and a porous carbon matrix are synthesized simply by annealing CuGeO3 @dopamine in a H2 /Ar atmosphere. The introduction of the carbon layer and inactive alloying phase Cu3 Ge not only enhances the electrical conductivity of the Ge anode, but also reduces the volume change of Ge during the cell cycle as a buffer. In particular, the anode of this peapod-like Cu3 Ge/Ge@C shows an excellent long cycle life as well as outstanding capacity performance, with a discharge specific capacity up to 934 mA h g-1 after 500 cycles.

Self-Supported and Flexible Sulfur Cathode Enabled via Synergistic Confinement for High-Energy-Density Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have attracted much attention in the field of electrochemical energy storage due to their high energy density and low cost. However, the "shuttle effect" of the sulfur cathode, resulting in poor cyclic performance, is a big barrier for the development of Li-S batteries. Herein, a novel sulfur cathode integrating sulfur, flexible carbon cloth, and metal-organic framework (MOF)-derived N-doped carbon nanoarrays with embedded CoP (CC@CoP/C) is designed. These unique flexible nanoarrays with embedded polar CoP nanoparticles not only offer enough voids for volume expansion to maintain the structural stability during the electrochemical process, but also promote the physical encapsulation and chemical entrapment of all sulfur species. Such designed CC@CoP/C cathodes with synergistic confinement (physical adsorption and chemical interactions) for soluble intermediate lithium polysulfides possess high sulfur loadings (as high as 4.17 mg cm-2 ) and exhibit large specific capacities at different C-rates. Specially, an outstanding long-term cycling performance can be reached. For example, an ultralow decay of 0.016% per cycle during the whole 600 cycles at a high current density of 2C is displayed. The current work provides a promising design strategy for high-energy-density Li-S batteries.

Controllable Hydrolysis Performance of MgLi Alloys and Their Hydrides.

Theoretically, the hydrolysis of MgLi and MgH2 -LiH can produce 9.6 and 17.5 wt.% hydrogen (water is not included in the calculation), respectively. The ball-milling method is commonly used to refine the particle size and thus may improve hydrolysis kinetics. However, Mg and Li will be easily agglomerated, which means that direct ball-milling could not refine MgLi. In this work, we introduced 10 wt.% expanded graphite into the ball-milling process to synthesize refined MgLi alloy samples. Further studies showed that MgLi-10 wt.% expanded graphite can produce 966 mL/g hydrogen within 3 min in 0.5 M MgCl2 solution. The MgLi hydrides were synthesized by reactive ball milling under 3 MPa H2 and their hydrolysis performance was investigated. Moreover, the sawed powder was milled in 3 MPa H2 for 6 h and then hydrogenated in 3 MPa H2 at 380 °C; it can produce 1542 and 1773 mL/g (15.8 wt.%) hydrogen in 5 and 30 min with mild kinetics, respectively, and the activation energy of the hydrolysis reaction is 24.6 kJ/mol in 1 M MgCl2 solution. The findings here open a new avenue to the development of refined MgLi alloys and hydrides for hydrogen generation through a controllable hydrolysis process.

Co-Substitution Enhances the Rate Capability and Stabilizes the Cyclic Performance of O3-Type Cathode NaNi0.45- xMn0.25Ti0.3Co xO2 for Sodium-Ion Storage at High Voltage.

O3-type NaNiO2-based cathode materials suffer irreversible phase transition when they are charged to above 4.0 V in sodium-ion batteries. To solve this problem, we partially substitute Ni2+ in O3-type NaNi0.45Mn0.25Ti0.3O2 by Co3+. NaNi0.45Mn0.25Ti0.3O2 with co-substitution possesses an expanded interlayer and exhibits higher rate capability, as well as cyclic stability, compared with the pristine cathode in 2.0-4.4 V. The optimal NaNi0.4Mn0.25Ti0.3Co0.05O2 delivers discharge capacities of 180 and 80 mA h g-1 at 10 and 1000 mA g-1. At 100 mA g-1, NaNi0.4Mn0.25Ti0.3Co0.05O2 exhibits 152 mA h g-1 in the initial cycle and maintains 91.4 mA h g-1 after 180 cycles. Through ex situ X-ray diffraction, co-substitution is demonstrated to be effective in enhancing the reversibility of P3-P3″ phase transition from 4.0 to 4.4 V. Electrochemical impedance spectroscopy indicates that higher electronic conductivity is achieved by co-substitution. Moreover, cyclic voltammetry and the galvanostatic intermittent titration technique demonstrate faster kinetics for Na+ diffusion due to the co-substitution. This study provides a reference for further improvement of electrochemical performance of cathode materials for high-voltage sodium-ion batteries.

A fleeting glimpse of the dual roles of SiB4 in promoting the hydrogen storage performance of LiBH4.

In this study, the positive effects and dual roles of SiB4 on the dehydrogenation and rehydrogenation performance of the LiBH4-SiB4 system are reported. Characterizations were performed through temperature programmed desorption mass spectrometry (TPD-MS), isothermal kinetics measurements, and XRD and FTIR analyses. For the hydrogen desorption from LiBH4, SiB4 played the role of a catalyst to kinetically facilitate the structural destabilization of LiBH4 and its intermediate phase Li2B12H12. Accordingly, a dehydrogenation capacity of 2.24 at. H/f.u. LiBH4 (close to 10.3 wt% H) was attained at a relative temperature of 350 °C. For hydrogen absorption to generate LiBH4, SiB4 was unexpectedly found to act as a reactant to thermodynamically improve the rehydrogenation process by reacting with LiH under moderate conditions of 10 MPa H2 and 400 °C, and a superior reversible capacity of 2.16 at. H/f.u. LiBH4 was achieved. These experimental results remind us to take into account the explicit role(s) of the employed components during the dehydrogenation and rehydrogenation reactions when designing a desirable LiBH4-based system.

FeP@C Nanotube Arrays Grown on Carbon Fabric as a Low Potential and Freestanding Anode for High-Performance Li-Ion Batteries.

An anode of self-supported FeP@C nanotube arrays on carbon fabric (CF) is successfully fabricated via a facile template-based deposition and phosphorization route: first, well-aligned FeOOH nanotube arrays are simply obtained via a solution deposition and in situ etching route with hydrothermally crystallized (Co,Ni)(CO3 )0.5 OH nanowire arrays as the template; subsequently, these uniform FeOOH nanotube arrays are transformed into robust carbon-coated Fe3 O4 (Fe3 O4 @C) nanotube arrays via glucose adsorption and annealing treatments; and finally FeP@C nanotube arrays on CF are achieved through the facile phosphorization of the oxide-based arrays. As an anode for lithium-ion batteries (LIBs), these FeP@C nanotube arrays exhibit superior rate capability (reversible capacities of 945, 871, 815, 762, 717, and 657 mA h g-1 at 0.1, 0.2, 0.4, 0.8, 1.3, and 2.2 A g-1 , respectively, corresponding to area specific capacities of 1.73, 1.59, 1.49, 1.39, 1.31, 1.20 mA h cm-2 at 0.18, 0.37, 0.732, 1.46, 2.38, and 4.03 mA cm-2 , respectively) and a stable long-cycling performance (a high specific capacity of 718 mA h g-1 after 670 cycles at 0.5 A g-1 , corresponding to an area capacity of 1.31 mA h cm-2 at 0.92 mA cm-2 ).

Correlation between structural stability of LiBH4 and cation electronegativity in metal borides: an experimental insight for catalyst design.

Nanosized metal borides MBx (M = Mg, Ti, Fe, Si) are found to play an important role in enhancing the hydrogen storage performance of LiBH4 in this work. The hydrogen storage behavior and mechanism of these modified systems are investigated through TPD-MS, XRD, FTIR and SEM characterization methods. By introducing these metal borides into LiBH4 through ball milling, the systems display three dehydrogenation stages disclosing their similarity and distinction. The 1st stage starts at 190 °C, the 2nd stage ranges from 280 °C to 400 °C and the 3rd stage ends at 550 °C with a peak at round 440 °C similar to that of pristine LiBH4. Distinguishing features exist at the 2nd stage revealing the effectiveness of MBx in an order of MgB2 < TiB2 < FeB < SiB4. Significantly, reversibility up to 9.7 wt% is achieved from LiBH4 with assistance of SiB4. The catalytic effect of MBx is influenced by the Pauling electronegativity of M in MBx and the interfacial contact characteristic between LiBH4 and MBx. The larger electronegativity leads to an enhanced catalytic effect and consequently lower temperature at the major stage. In contrast to the components in the solid state, the molten LiBH4 promotes a catalytic effect due to a superior interfacial contact. These results provide an insight into designing high-performance catalysts applied to LiBH4 as a hydrogen storage material.

Silver@Nitrogen-Doped Carbon Nanorods as a Highly Efficient Electrocatalyst for the Oxygen Reduction Reaction in Alkaline Media.

In recent years, various platinum-free catalysts for the oxygen reduction reaction (ORR) have attracted great attention due to the limited natural abundance and high cost of platinum. Herein, Ag@N-C (N-C: nitrogen-doped carbon) nanorods for the ORR were synthesized through chemical polymerization and pyrolysis methods by using pyrrole and silver nitrate as raw materials. Pyrolysis could significantly increase the specific surface area of as-synthesized catalysts and convert pyrrolic-N into graphitic-N and pyridinic-N. The results of electrochemical tests show that the Ag@N-C-900 catalyst (pyrolyzed at 900 °C) exhibits highly efficient ORR catalytic activity, improved stability, and better methanol resistance in comparison to that of Pt/C catalyst in alkaline media.