Zhong-Li Wang

Tailoring deposition and morphology of discharge products towards high-rate and long-life lithium-oxygen batteries

Lithium-oxygen batteries are an attractive technology for electrical energy storage because of their exceptionally high-energy density; however, battery applications still suffer from low rate capability, poor cycle stability and a shortage of stable electrolytes. Here we report design and synthesis of a free-standing honeycomb-like palladium-modified hollow spherical carbon deposited onto carbon paper, as a cathode for a lithium-oxygen battery. The battery is capable of operation with high-rate (5,900 mAh g ⁻¹ at a current density of 1.5 A g⁻¹) and long-term (100 cycles at a current density of 300 mA g⁻¹ and a specific capacity limit of 1,000 mAh g⁻¹). These properties are explained by the tailored deposition and morphology of the discharge products as well as the alleviated electrolyte decomposition compared with the conventional carbon cathodes. The encouraging performance also offers hope to design more advanced cathode architectures for lithium-oxygen batteries.

Synthesis of Perovskite‐Based Porous La0.75Sr0.25MnO3 Nanotubes as a Highly Efficient Electrocatalyst for Rechargeable Lithium–Oxygen Batteries

Rechargeable lithium–oxygen (Li-O2) batteries have recently attracted great attention because they can theoretically store 5–10 times more energy than current lithium-ion batteries, which is essential for clean energy storage, electric vehicles, and other high-energy applications. However, to use Li-O2 batteries for practical applications, numerous scientific and technical challenges need to be surmounted. 8] In response, intensive research efforts have been made to address the challenges by incorporating metal oxides, metal nitrides, metal nanoparticles, 21] and organometallic compounds 22] as electrocatalysts in the O2 electrode. Although significant improvements in the oxygen-reductionreaction (ORR) and/or oxygen-evolution-reaction (OER) overpotentials have been achieved, there is still a demand for highly efficient electrocatalysts to further enhance the specific capacity, rate capability, and cyclic life especially at a high capacity. On the other hand, most of the catalyst performances reported thus far are tested using carbonate-based or mixed ether-carbonate-based electrolytes, which have now been shown to be not inert to the superoxide radical (O2C ) and thus are inevitably decomposed upon cell discharge/ charge. For example, Luntz and co-workers demonstrate that, when carbonate-based electrolytes are employed for LiO2 cells, the main role of the Au, Pt, and MnO2 catalysts is to catalyze the decomposition of the electrolytes. In this context, the development of OER and ORR electrocatalysts in a relatively stable electrolyte is thus of importance to realize a reversible Li-O2 battery. Compared to carbonate, ether-based electrolytes have been reported to be more suitable for Li-O2 batteries because the desired lithium peroxide is the dominant product. 29] However, there are not many reports on electrocatalysts for Li-O2 batteries with ether-based electrolytes. 10, 30, 33] Perovskite oxides have a high electronic/ionic conductivity and catalytic activity and thus could be a promising candidate as electrocatalyst for Li-O2 batteries. [33–35] Herein, we firstly propose and realize a facile, effective, and scalable strategy for preparing perovskite-based porous La0.75Sr0.25MnO3 nanotubes (PNT-LSM) by combining the electrospinning technique with a heating method. Figure 1

In Situ Fabrication of Porous Graphene Electrodes for High-Performance Energy Storage

In the development of energy-storage devices, simultaneously achieving high power and large energy capacity at fast rate is still a great challenge. In this paper, the synergistic effect of structure and doping in the graphene is demonstrated for high-performance lithium storage with ulftrafast and long-cycling capabilities. By an in situ constructing strategy, hierarchically porous structure, highly conductive network, and heteroatom doping are ideally combined in one graphene electrode. Compared to pristine graphene, it is found that the degree of improvement with both structure and doping effects is much larger than the sum of that with only structure effect or doping effect. Benefitting from the synergistic effect of structure and doping, the novel electrodes can deliver a high-power density of 116 kW kg(-1) while the energy density remains as high as 322 Wh kg(-1) at 80 A g(-1) (only 10 s to full charge), which provides an electrochemical storage level with the power density of a supercapacitor and the energy density of a battery, bridging the gap between them. Furthermore, the optimized electrodes exhibit long-cycling capability with nearly no capacity loss for 3000 cycles and wide temperature features with high capacities ranging from -20 to 55 °C.

Integrated Three-Dimensional Carbon Paper/Carbon Tubes/Cobalt-Sulfide Sheets as an Efficient Electrode for Overall Water Splitting

The development of an efficient catalytic electrode toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of great significance for overall water splitting associated with the conversion and storage of clean and renewable energy. In this study, carbon paper/carbon tubes/cobalt-sulfide is introduced as an integrated three-dimensional (3D) array electrode for cost-effective and energy-efficient HER and OER in alkaline medium. Impressively, this electrode displays superior performance compared to non-noble metal catalysts reported previously, benefiting from the unique 3D array architecture with increased exposure and accessibility of active sites, improved vectorial electron transport capability, and enhanced release of gaseous products. Such an integrated and versatile electrode makes the overall water splitting proceed in a more direct and smooth manner, reducing the production cost of practical technological devices.

3D ordered macroporous LaFeO3 as efficient electrocatalyst for Li–O2 batteries with enhanced rate capability and cyclic performance

Rechargeable lithium–oxygen (Li–O2) battery is one of the most promising technologies among various electrochemical energy storage systems, while the incapability of the electrocatalyst and the inefficient transport of reactants in the O2 electrode still limit the round-trip efficiency, rate capability, and cycle stability of the Li–O2 battery. Here, three-dimensional ordered macroporous LaFeO3 (3DOM-LFO) is synthesized and employed as electrocatalyst in Li–O2 battery with relatively stable TEGDME based electrolyte. The Li–O2 cells with 3DOM-LFO show enhanced electrochemical performances, including low overpotential, high specific capacity, good rate capability and cycle stability up to 124 cycles. This enhanced catalytic performance might be due to the synergistic effect of the porosity and catalytic activity of the 3DOM-LFO catalyst.

Synergistic Effect between Metal-Nitrogen-Carbon Sheets and NiO Nanoparticles for Enhanced Electrochemical Water-Oxidation Performance

Identifying effective means to improve the electrochemical performance of oxygen-evolution catalysts represents a significant challenge in several emerging renewable energy technologies. Herein, we consider metal-nitrogen-carbon sheets which are commonly used for catalyzing the oxygen-reduction reaction (ORR), as the support to load NiO nanoparticles for the oxygen-evolution reaction (OER). FeNC sheets, as the advanced supports, synergistically promote the NiO nanocatalysts to exhibit superior performance in alkaline media, which is confirmed by experimental observations and density functional theory (DFT) calculations. Our findings show the advantages in considering the support effect for designing highly active, durable, and cost-effective OER electrocatalysts.

C and N Hybrid Coordination Derived Co–C–N Complex as a Highly Efficient Electrocatalyst for Hydrogen Evolution Reaction

Development of an efficient hydrogen evolution reaction (HER) catalyst composed of earth-abundant elements is scientifically and technologically important for the water splitting associated with the conversion and storage of renewable energy. Herein we report a new class of Co-C-N complex bonded carbon (only 0.22 at% Co) for HER with a self-supported and three-dimensional porous structure that shows an unexpected catalytic activity with low overpotential (212 mV at 100 mA cm(-2)) and long-term stability, better than that of most traditional-metal catalysts. Experimental observations in combination with density functional theory calculations reveal that C and N hybrid coordination optimizes the charge distribution and enhances the electron transfer, which synergistically promotes the proton adsorption and reduction kinetics.

Electrostatic Induced Stretch Growth of Homogeneous β -Ni(OH) 2 on Graphene with Enhanced High-Rate Cycling for Supercapacitors

Supercapacitors, as one of alternative energy devices, have been characterized by the rapid rate of charging and discharging, and high power density. But they are now challenged to achieve their potential energy density that is related to specific capacitance. Thus it is extremely important to make such materials with high specific capacitances. In this report, we have gained homogenous Ni(OH)2 on graphene by efficiently using of a facile and effective electrostatic induced stretch growth method. The electrostatic interaction triggers advantageous change in morphology and the ordered stacking of Ni(OH)2 nanosheets on graphene also enhances the crystallization of Ni(OH)2. When the as-prepared Ni(OH)2/graphene composite is applied to supercapacitors, they show superior electrochemical properties including high specific capacitance (1503 F g−1 at 2 mV s−1) and excellent cycling stability up to 6000 cycles even at a high scan rate of 50 mV s−1.

Rhodium-nickel nanoparticles grown on graphene as highly efficient catalyst for complete decomposition of hydrous hydrazine at room temperature for chemical hydrogen storage

Well-dispersed rhodium–nickel nanoparticles grown on graphene are successfully synthesized by co-reduction of graphene oxide and metal precursors, wherein graphene proved to be a powerful dispersion agent and distinct support for the RhNi nanoparticles. Unexpectedly, the resultant RhNi@graphene catalyst exerts 100% selectively and exceedingly high activity to complete the decomposition reaction of hydrous hydrazine at room temperature. This excellent catalytic performance might be due to the synergistic effect of the graphene support and the RhNi nanoparticles and the promotion effect of NaOH. The utilization of graphene as a novel two-dimensional catalyst support to anchor active component nanoparticles and thus to facilitate the electron transfer and mass transport kinetics during the catalytic reaction process opens up new avenues for designing next-generation catalysts.

Reactive Multifunctional Template‐Induced Preparation of Fe‐N‐Doped Mesoporous Carbon Microspheres Towards Highly Efficient Electrocatalysts for Oxygen Reduction

A novel in situ replication and polymerization strategy is developed for the synthesis of Fe-N-doped mesoporous carbon microspheres (Fe-NMCSs). This material benefits from the synergy between the high catalytic activity of Fe-N-C and the fast mass transport of the mesoporous microsphere structure. Compared to commercial Pt/C catalysts, the Fe-NMCSs show a much better electrocatalytic performance in terms of higher catalytic activity, selectivity, and durability for the oxygen reduction reaction.