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This is the first study of the catalytic graphitization of Black Spruce (Picea mariana) which has successfully discovered the formation of single crystal graphitic carbon structures with a very high conductivity over 850 S/m implemented in the cathode of a coin cell battery. Renewable carbon with this conductivity is suitable for use in bio-electronics, organic thin film transistors, fuel cells, organic batteries, supercapacitors and sensing device applications. The P. mariana was doped with iron nitrate nanoparticle precursor, and sequentially thermo-catalyzed in presence of helium at temperatures between 300 and 800 °C. Transmission electron micrographs reveal formation of graphitic structures with an interplanar distance of ∼0.33 nm resembling single crystal graphite structure. Raman spectroscopy and X-ray diffraction studies confirm the presence of nano-layered carbon, and the high conductivity was observed in Fe-free residual graphite. Thus, using iron nitrate as a catalyst promotes the formation of single crystal graphitic structures at a significantly reduced thermal energy than traditional pyrolysis treatment and opens a new frontier for sustainable bio-electronics and energy materials manufacturing.

It is fairly desired but remains challenging to synthesize metal selenides with nanosized building blocks via simplified approaches which make more active sites exposed to electrolytes for achieving high-efficient electrocatalysts for oxygen evolution reaction (OER). Herein, on the basis of the Kirkendall effect, we developed a simple synthesis of yolk-shell nanostructured nickel-cobalt diselenides (NiCoSe2) with nanosized wide annular aisles via one-step electrodeposition. Expressly, the electronic coupling between Ni and Co cations was well regulated via the optimization of Ni/Co atomic ratios to regulate eg filling of Ni for optimized OER. The elaborate yolk-shell nanostructured NiCoSe2 catalyst exhibits remarkable OER performance, delivering a low overpotential of 249 mV at a geometric current density of 10 mA cm−2 in alkaline media, a small Tafel slope of 43 mV dec−1 and a decent durability with a tiny decay of 23 mV over 20 h electrolysis. The Kirkendall effect-induced formation route of the yolk-shell nanostructure will provide helpful guidance for the rational design of hollow structured catalyst in the field of energy catalysis and other extended applications.

Replacing sluggish oxygen evolution reaction with thermodynamically favorable urea oxidation reaction is a promising strategy for hydrogen-generation from water with low-energy consumption. However, the involved six-electron transfer process makes it formidable and seems critical. Hence, exploring high-efficient and low-cost bifunctional catalysts toward urea electrolysis is highly desirable. Herein, hierarchical cuprous sulfide@nickel selenide nanowire arrays were grown on copper foam (termed as Cu2S@Ni3Se2) via a developed method composed of in situ chemical deposition, ion exchange and electrodeposition. The as-prepared bifunctional Cu2S@Ni3Se2 not only shows remarkable hydrogen evolution reaction (HER) activity but also affords excellent urea oxidation reaction (UOR) activity. A subsequently configured Cu2S@Ni3Se2//Cu2S@Ni3Se2 full-cell (Cu2S@Ni3Se2 working as both anode and cathode) only requires a low voltage of 1.48 V to launch a current density of 10 mA cm−2, not only surpassing the routine water electrolysis (1.70 V), but also outperforming the state-of-the-art Pt/C//IrO2 for urea electrolysis (1.65 V). Moreover, the performance is superior to most recently reported ones that configured with other catalysts. This work presents a solid step for hydrogen-generation from water with low-energy consumption.

Perovskite oxides have been recognized as one of the most attractive oxygen evolution reaction (OER) catalysts because of their low cost, earth abundance, and robust nature. Herein, one-dimensional porous LaFe1-xNixO3 (LFNO) perovskite oxide nanofibers (LFNO NFs) are fabricated with a feasible electrospinning route and its further post-calcination treatment. By tailoring the atomic percent of Fe and Ni in the perovskite oxide, we determined that LaFe0.25Ni0.75O3 (LFNO-III) NFs afford the best OER activity among all the prepared perovskite oxides. Especially remarkable is that the further selenide-doped LaFe0.25Ni0.75O3 (LFNOSe-III) NFs exhibit outstanding OER activity with a low overpotential of 287 mV at 10 mA cm-2 and a small Tafel slope of 87 mV dec-1 in 1 M KOH solution, markedly exceeding that of the parent perovskite oxide and the commercial RuO2. It also delivers decent durability with no significant degradation after 22 h of stability test. In the meanwhile, density functional theory calculations are also conducted to justify the optimized adsorption features of *OH, *O, and *OOH intermediates and unveil that the electrocatalytic active sites are the Ni atoms adjacent to Fe in the Ni- and Se codoped perovskite. This work provides an effective method for the development of highly efficient perovskite oxide catalysts.

In this work, we demonstrated that titanium silicalite-1 (TS-1) crystal planes affected the activity of nanogold supported on TS-1 (denoted as Au/TS-1) for direct propylene epoxidation with H2 and ...

Exploration of highly efficient and stable photocatalysts for water splitting has attracted much attention. However, developing a facile and effective approach to enhance the photocatalytic activity for practical applications is still highly challenging. Herein, we report a newly-fabricated perovskite oxide (Pr0.5(Ba0.5Sr0.5)0.5Co0.8Fe0.2O3) decorated with Au ultrafine nanoparticles for photocatalytic water splitting. An exceptionally high hydrogen evolution rate of 1618 μmol g-1 h-1 was achieved (under 2 h illumination) when the Au mass loading was optimized to 9.3 wt%, which is 540 times higher than that of the pristine one. The splendid photocatalytic activity of the sample was attributed to plasmon-excited hot electron injection from Au to Pr0.5(Ba0.5Sr0.5)0.5Co0.8Fe0.2O3 (PBSCF) under illumination. The finite-difference time-domain simulations (FDTD) demonstrated that the localized strong electric field formed at the interface between Au and PBSCF under illumination, enables the hot electrons to be energetic and make the injection possible.

Designing high efficient and noble metal-free bifunctional electrocatalysts for both hydrogen and oxygen generation is still critical and challenged. In this study, hierarchical dodecahedral-structured CoP/CN@MoS2 is prepared through a two-step calcination treatment and a solvothermal approach. The metal-organic framework of ZIF-67 is chosen to serve as the template and for providing Co sources, in which ZIF-67 is first transformed to Co nanoparticles embedded in nitrogen-doped carbon polyhedrons and then transformed to CoP/CN. MoS2 nanosheets are further grown on the surface of dodecahedral-structured CoP/CN with a solvothermal method. Benefiting from the synergistic coupling effect of CoP and MoS2 and the nitrogen-doped carbon matrix, advanced hydrogen evolution reaction (HER) both in acid and alkaline solution as well as splendid oxygen evolution reaction (OER) performance in alkaline aqueous were achieved. Moreover, the coupling effect of CoP/CN and MoS2 is disclosed theoretically by density functional theory calculations to validate the increased HER activity. The as-prepared hybrid CoP/CN@MoS2 not only exhibits decent HER activity in acidic (η10 = 144 mV) and alkaline solutions (η10 = 149 mV), but also exhibits splendid OER activity (η10 = 289 mV) in 1.0 M KOH. This work represents a solid step toward boosting the electrocatalytic kinetics of nonprecious catalysts.

Exploitation of earth-abundant, cost-effective and high-efficient bifunctional electrocatalysts for overall water spitting in basic media is highly desirable, yet it remains a big challenge. Here, NiFe Layered-double-hydroxide nanosheet-anchored CoSe nanotubes (composed of plicated nanosheets) supported on Ni foam are prepared through our developed hydrothermal-selenization-hydrothermal method. Benefiting from the unique nanoarchitecture, optimized adsorption/desorption of oxygenated species at the interface (owing to the re-delocalization of electron spin status via π-donation), the bifunctional hybrid catalysts exhibit low overpotentials of 201 and 98 mV at 10 mA cm−2 for oxygen evolution reaction and hydrogen evolution reaction in 1 M KOH aqueous solution, respectively. Particularly, the full-cell only requires 1.53 V to drive a current density of 10 mA cm−2 when choosing the hybrid catalysts serving as both anode and cathode, being superior than that of the state-of-the-art commercial noble-metal based cells for overall water splitting. This work presents a general strategy to boost the oxygen evolution reaction and hydrogen evolution reaction kinetics of selenides, which is also expected to extend to other noble-metal-free catalysts.

Catalysts with core–shell structure are particularly attractive because nanoparticles (NPs) can be protected against sintering by a thin zeolite shell. Titanium silicalite-1 coated with silicalite-...

Solid oxide fuel cell (SOFC) is an advanced electricity generation device with attractive fuel flexibility and conversion efficiency. As its reversed process, solid oxide electrolysis cell (SOEC) can efficiently electrolyze notorious CO2 to valuable chemical product such as CO, by utilizing renewable energy. To achieve long-term operation, the development of catalytically active electrode materials in both SOFC/SOEC modes is highly desirable, yet still challenging. In this research, an A-site deficient perovskite oxide (lanthanum chromite) decorated with in-situ exsolved Ni-Co nano-alloy has been fabricated and applied as a potential fuel electrode for both SOFC/SOEC. The influences of A-site non-stoichiometry and B-site dopant concentration on structural properties and in-situ exsolution process have been elaborately studied from various aspects. Diverse characterizations collectively confirm that the existence of A-site deficiency helps the formation of oxygen vacancies and stimulates the exsolution of B-site cations. In addition, the synergistic effect between the dopants of Co and Ni manipulates the reducibility and promotes carbon deposition resistance of the material. The electrolyte-supported SOFC with self-assembled Ni-Co nano-alloy electrode has shown maximum power densities of 329 mW/cm2 (in H2) and 258 mW/cm2 (in syngas, H2 + CO) at 850 °C, which are 50% better than those of the fuel cell with the exsolved Ni nanoparticles only. Also, the nano-alloy decorated electrode catalyst promotes a 30% increase in SOEC performance for CO2 electrolysis with prominently enhanced resistance against carbon deposition, suggesting the versatile functionality of the materials.

Real bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) should be the ones that exhibit an immortal behavior during catalysis without structural transformation or surface reconstruction. Otherwise, they could be only termed as “pre-catalysts” rather than the real catalysts. Herein, single-atom dispersed catalysts (SACs) embedding atomically dispersed Ru onto nickel-vanadium layered double hydroxide matrix (termed as Ru/Ni3V-LDH) not only exhibit excellent HER activity (~ 54.3 fold mass activity vs. the commercial Pt/C) and OER activity, but also possess decent full-cell performance for overall water splitting (1.5 V@10 mA cm-2). Most importantly, in-situ XAS and Raman spectroscopic studies clarified that, unlike numerous bifunctional catalysts that have suffered from the structural reconstruction/transformation for adapting the HER/OER cycles, Ru/Ni3V-LDH is characteristic of immortally dual reactive sites (i.e., Ru and Ni sites) for individual catalysis of electrochemical water splitting and could be termed as the real bifunctional electrocatalyst.

High-efficient electrocatalysts are crucial for fuel cell applications; however, the whole cell performance is generally restricted by the anodic part because of the sluggish kinetics involved in the oxygen evolution reaction (OER) process. Herein, a hierarchical hollow (Co,Ni)Se2@NiFe layered double hydroxide (LDH) nanocage was synthesized by deriving from the metal–organic framework (MOF) of ZIF-67. Concretely, it involves first fabrication of hollow rhombic (Co,Ni)Se2 nanocages and then deposition of NiFe LDH nanosheets on the surface of nanocages. Notably, the incorporation of Ni into Co-based ZIF-67 (via ion-exchange) could tail the atomic arrangement of the MOF, exposing more additional active sites in the following selenization treatment. The as-synthesized (Co,Ni)Se2@NiFe LDH demonstrates splendid OER performance with a small overpotential of 277 mV (to launch a current density of 10 mA cm–2), a small Tafel slope of 75 mV dec–1, and robust durability (a slight stability decay of 5.1% after 17 h of...

The scarcity and weak durability of precious metal catalysts are among the biggest obstacles to achieving cost-effective electrocatalysts in fuel cells and metal–air batteries. Hence, it is imperative to develop low-cost non-precious metal catalysts with comparable oxygen reduction reaction (ORR) activity to precious metal catalysts. Herein, we report a highly effective strategy for the facile synthesis of Fe/N-functionalized 3D porous carbon networks. A major advantage of the newly designed catalyst is that ultrafine Fe4N nanoparticles are grown and uniformly mounted on the carbon framework upon pyrolysis treatment at 800 °C, and co-exist with numerous in situ formed Fe–N4 moieties in the carbon matrix, being evidenced by using X-ray absorption and photoelectron spectroscopy. The new electrocatalysts exhibit high ORR activity, comparable/superior to that of the state-of-the-art Fe/N–carbon based catalysts reported to date. Specifically, the catalysts show a half-wave potential of 0.890 V (vs. RHE) and a limited current density of 6.18 mA cm−2. By resorting to experimental measurements and density-functional theory (DFT) calculations, the synergistic effects between Fe–N4 moieties and the Fe4N support are identified for the first time, which play a key role in boosting the catalytic performance of the Fe/N-functionalized porous carbon networks.

Hydrogen, regarded as one of the most promising green and sustainable energy resources, could be generated by splitting water with electrochemical methods. The challenge for efficient hydrogen generation is the sluggish kinetics at the anodes for the oxygen evolution reaction (OER). Here, a novel catalyst with remarkably enhanced OER activity was prepared by coupling FeOOH and NiCoP/C. The enhanced OER activity of the hybrid catalyst should be ascribed to the synergistic effect of the individual components. First, NiCoP/C derived from ZIF-67 with a hollow rhombic dodecahedral architecture not only allows exposure of numerous active sites but also provides high conductivity. Second, the re-localization of electrons at the coupling interface optimizes the adsorption/desorption nature of intermediate oxygenated species and imparts a high OER activity. The hybrid NiCoP/C@FeOOH catalyst exhibits very high OER activity with a low overpotential of 271 mV for producing a current density of 10 mA cm-2 in 1 M KOH aqueous solution, markedly surpassing the individual counterparts of pure NiCoP/C nanocages and bare FeOOH. This work represents a universal strategy for boosting the OER kinetics of catalysts and pushing boundaries for high-efficiency water oxidation.

In view of the high theoretical specific capacity of 946 mAh/g, Sb2S3 anode materials have been considered as competitive candidates for high performance lithium ion batteries (LIBs). However, pure Sb2S3 usually suffers from inferior cyclicity because of the extremely large volume expansion upon Li+ uptake and release processes when applied as electrode in LIBs. Combining Sb2S3 with carbonaceous materials would reduce the volume change effect and thus maintains high capacity and substantially improves the cycling performance. Herein, ultrafine Sb2S3 nanoparticles embedded in mesoporous hollow carbon spheres (MHCS) are successfully prepared based on a facile hydrothermal method using MHCS as the microreactor for lithium ion storage, which delivers a desirable specific capacity of 745.3 mAh/g at a current density of 100 mA/g after 160 cycles, and displays prominent rating capability. The outstanding electrochemical performance is due to the mesoporous and unique hollow feature of MHCS, which not only facilitates the electron transfer and Li+ diffusion, but also confines the growth of Sb2S3.

It is highly desired while remains challenging to explore stable, earth-abundant, low-cost, and high-efficient electrocatalysts towards eco-friendly utilization of green energy. In this study, we report a one-pot hydrothermal synthesis of polyvinyl-pyrrolidone (PVP)-decorated nickel-iron diselenide hollow nanoparticles with strongly hydrophilic surface, the hollow architecture of which could be assigned to the Kirkendall effect. As the lactam groups in PVP are strongly polar and incline to interact with water molecules, the surface wettability of the electrocatalyst was effectively improved after PVP was introduced. Compared with the pristine one, such PVP decorated nickel-iron diselenide hollow nanoparticles demands only a low overpotential of 255 mV to drive a geometrical current density of 10 mA cm−2 in 1 M KOH aqueous solution. Moreover, this PVP involved electrocatalyst yields a low Tafel slope of 56 mV dec−1 and possesses remarkably long-term durability. This surface engineering insight provides an indication for fabrication of high-efficient OER electrocatalysts.

Exploring low-cost, high-efficient and durable electrocatalysts to substitute for Ru, Ir-based noble metal catalysts is of great significance for oxygen evolution reaction (OER), which is in particular a sluggish anodic process in water oxidation and remains to be a major challenge that we are confronted with. Herein, we report nickel-iron diselenide hollow nanochains (denoted as NFSHNCs) synthesized via a two-step hydrothermal method working as the high performance OER catalyst. The formation of well-shaped NFSHNCs is due to the Kirkendall effect, in which NiFe alloy solid nanochains were employed as the precursors. The as-prepared NFSHNCs not only exhibit outstanding OER performance with low overpotential of 267 mV (at a current density of 10 mA cm−2) and small Tafel slope of 67 mV dec−1, superior to the state-of-the-art commercial RuO2, but also deliver high durability with a dinky degradation of 5.3% after 12 h fierce test. To identify the electrocatalytic active sites, the Gibbs free energy differences (ΔG) related to the O* and OH* adsorption on NiFe selenides were calculated with density functional theory. The theoretical results corroborate the fact that the O* and OH* adsorption prefers to occur on both iron sites and the nickel sites (the one that in the vicinity of iron sites) because of the synergistic effects of electron configuration.

The strong desire for a clean and secure energy future has stimulated great interest in searching for low-cost, highly efficient electrocatalysts for regenerative fuel cells and rechargeable metal-air batteries. Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play a paramount role in the operation of these devices, but are notoriously sluggish even with precious metals-based catalysts. Here we report our findings in the development of a bifunctional catalyst based on phosphorus-doped LaFeO3-δ for ORR and OER in alkaline solutions. The remarkable electrocatalytic performance is attributed to larger amount of O22−/O− species, trace amount of Fe4+ species, and optimized eg electron filling (≈ 1), benefiting from the doping effect of phosphorus. Both the mass activity and the specific activity are nearly doubled after P-doping. Density functional theory calculations also confirm that the increase in valence state of Fe ions is due mainly to phosphorus doping. These results demonstrate that non-metal element doping is an effective approach to optimizing the electronic configuration, changing valence states of ions, and thus enhancing activities of perovskite electrocatalysts.

Oxygen is the most abundant element in the Earth’s crust. The oxygen reduction reaction (ORR) is also the most important reaction in life processes and energy converting/storage systems. Developing techniques toward high-efficiency ORR remains highly desired and a challenge. Here, we report a N-doped carbon (NC) encapsulated CeO2/Co interfacial hollow structure (CeO2–Co–NC) via a generalized strategy for largely increased oxygen species adsorption and improved ORR activities. First, the metallic Co nanoparticles not only provide high conductivity but also serve as electron donors to largely create oxygen vacancies in CeO2. Second, the outer carbon layer can effectively protect cobalt from oxidation and dissociation in alkaline media and as well imparts its higher ORR activity. In the meanwhile, the electronic interactions between CeO2 and Co in the CeO2/Co interface are unveiled theoretically by density functional theory calculations to justify the increased oxygen absorption for ORR activity improvement....

In this work, Cu2ZnSnS4 (CZTS) thin films were grown on Mo-coated Soda-lime-glass (SLG) substrates by annealing of sputtered ZnS/Sn/CuS precursors at 580 ℃ for 15 min. As a try, the CZTS solar cells were fabricated using simple structure of Mo-coated SLG/CZTS/CdS/Al and traditional structure of Mo-coated SLG/CZTS/CdS/i-ZnO/In2O3:SnO2 (ITO)/Al, respectively. The results show that the CZTS device with simple structure can achieve same level of the open circuit voltage (Voc) compared with that of traditional structure. In addition, the power conversion efficiency of 2.95% and 3.59% were obtained with simple structure and traditional structure, respectively. The CZTS solar cell with simple structure provides a promising way and an easy process to prepare high-performance CZTS thin film solar cells which is available to large-scale industrial production in the future.

The nature of gold active sites on Au–Ti catalysts dictates the reactivity and selectivity during propylene epoxidation reactions. The type of the sites and the location of Au clusters on the external surfaces of TS-1 or inside the TS-1 nanopores have remained the topic of interest. We synthesized and characterized dispersed Au clusters on titanium silicate-1 (Au/TS-1), uncalcined TS-1 (Au/un TS-1), and TS-1 coated with silicalite-1 (Au/S-1/TS-1) to probe the nature of gold active sites for gas-phase epoxidation of propylene. The results of Au/TS-1 and Au/S-1/TS-1 show the importance of Au nanoclusters (

Considering the weak rigidity of blisk blades and the limited accessibility of blisk tunnels, polishing blisk blades is difficult when using tools with poor flexibility and large dimension. Hence, to reduce the Surface roughness (SR) of a blisk blade, five-axis polishing method with Abrasive belt flap wheel (ABFW) is employed to polish the blisk blade based on the analysis of the blisk structure and advantages of ABFW polishing. Polishing experiments based on central composite design are performed using ABFW. Response surface method (RSM) is employed to establish a predictive model between SR and various parameters, including ABFW size, contact force, spindle speed, and feed rate. Analysis of variance is then performed to evaluate the proposed model. The degree of influence of each factor on SR after polishing using ABFW is determined by plotting main effects. The interactions of polishing factors on SR are analyzed by RSM. Optimal parameters are obtained by response surface optimization. Finally, an experiment on blisk blade polishing using ABFW on a five-axis polishing machine is carried out for confirmation. Results indicate that the surface quality of the blisk blade after polishing is significantly improved, with SR being less than 0.4 μm.

In this paper, the effects of two different sulfurization processes on the CZTS films were investigated, and the results indicated that a rapid high-temperature crystallization process after sulfurization was beneficial for CZTS thin films to obtain a compact and flat surface with large grains. However, a common sulfurization without rapid high-temperature crystallization process would easily lead to undesirable properties of films, such as rough surface with pin holes, which degenerate the performance of devices. Cu2ZnSnS4 (CZTS) solar cell based on a rapid high-temperature process after sulfurization achieved a high open circuit voltage of 722 mV and the best efficiency 3.32% was obtained.

Currently, most of investigations about CZTS focus on the sulfurization conditions, the precursor stacking orders, and effects of secondary phases on the device performance. However, very few researchers have a detailed investigation of sputtering period. In this paper, the effects of sputtering period on the performance of Cu2ZnSnS4 solar cells are discussed. The crystal structure, morphology, chemical composition and phase purity of CZTS thin films prepared by different periods were characterized by X-Ray Diffraction(XRD), scanning electron microscopy(SEM) equipped with an energy dispersive spectrometer(EDS) and Raman spectroscopy. The results show that the performances of CZTS devices prepared by multi periods were better than that of using single period. Meanwhile, complete devices were fabricated using CZTS thin film based on different sputtering periods, and 2.02% efficiency of CZTS by single period, 3.19% efficiency by double periods and 3.6% efficiency by four periods were obtained, respectively.

Single-atom catalysts (SACs) have emerged as one of the most promising alternatives to noble metal-based catalysts for highly efficient oxygen reduction reaction (ORR). While SACs can offer notable benefits in terms of lowering overall catalyst cost, there is still room for improvement regarding catalyst activity. To this end, we designed and successfully fabricated an ORR electrocatalyst in which atomic clusters are embedded in an atomically dispersed Fe-N-C matrix (FeAC@FeSA-N-C), as shown by comprehensive measurements using aberration-corrected scanning transmission electron microscopy (AC-STEM) and X-ray absorption spectroscopy (XAS). The half-wave potential of FeAC@FeSA-N-C is 0.912 V (versus reversible hydrogen electrode (RHE)), exceeding that of commercial Pt/C (0.897 V), FeSA-N-C (0.844 V), as well as the half-wave potentials of most reported non-platinum-group metal catalysts. The ORR activity of the designed catalyst stems from single-atom active centers but is markedly enhanced by the presence of Fe nanoclusters, as confirmed by both experimental measurements and theoretical calculations.

Water splitting is a green strategy for hydrogen generation but greatly hindered by the sluggish anodic oxygen evolution reaction (OER). Herein, ultrathin rhodium-doped nickel iron layered double hydroxide nanosheets are successfully synthesized, which exhibit outstanding hydrogen evolution reaction (HER) and OER performance, and advanced overall water splitting. More impressively, the remarkable mass activity of 960 mA mg1 at 1.55 V (1.7 times larger than NiFe-LDH) for urea electro-oxidation reaction (UOR) shows the great potential to surmount the sluggish OER for overall water splitting. A urine-mediated electrolysis cell is subsequently configured, delivering a current density of 10 mA cm-2 with a potential of 1.35 V, which is 105 mV lower than that of urea-free counterpart. The enhanced catalytic activity and cell performance are attributed to the introduction of Rh into NiFe-LDH matrix by changing the electronic structure, allowing optimization of the adsorbed species, as confirmed by experimental measurements and computational analyses.

Because of the advanced nature of their high power density, fast charge/discharge time, excellent cycling stability, and safety, supercapacitors have attracted intensive attention for large-scale applications. Nevertheless, one of the obstacles for their further development is their low energy density caused by sluggish redox reaction kinetics, low electroactive electrode materials, and/or high internal resistance. Here, we develop a facile and simple nitridation process to successfully synthesize hierarchical Ni nanoparticle decorated Ni0.2Mo0.8N nanorod arrays on a nickel foam (Ni–Mo–N NRA/NF) from its NiMoO4 precursor, which delivers a high areal capacity of 2446 mC cm−2 at a current density of 2 mA cm−2 and shows outstanding cycling stability. The superior performance of the Ni–Mo–N NRA/NF can be ascribed to the metallic conductive nature of the Ni–Mo nitride, the fast surface redox reactions for the electrolyte ions and electrode materials, and the low contacted resistance between the active materials and the current collectors. Furthermore, a hybrid supercapacitor (HSC) is assembled using the Ni–Mo–N NRA/NF as the positive electrode and reduced graphene oxide (RGO) as the negative electrode. The optimized HSC exhibits excellent electrochemical performance with a high energy density of 40.9 W h kg−1 at a power density of 773 W kg−1 and a retention of 80.1% specific capacitance after 6000 cycles. These results indicate that the Ni–Mo–N NRA/NF have a promising potential for use in high-performance supercapacitors.

In this study, the impacts of different precursors on Cu 2 ZnSnS 4 thin film solar cells were investigated. The two kinds of precursors of (Cu+Sn)/Zn and (Cu+Sn)/ZnS were deposited on Mo-coated soda lime glasses by magnetron sputtering. Cu 2 ZnSnS 4 (CZTS) films based on different precursors were fabricated by soft annealing and following two-step sulfurization in sulphur vapour. The crystal structure, phase purity, surface morphology, composition and optical properties of CZTS films from different precursors were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), energy dispersive spectrometry (EDS) and UV–vis–NIR spectroscopy, respectively. As a result, the CZTS thin films with smooth surface and uniform compositional ratio distribution were obtained from the precursors of (Cu+Sn)/ZnS. The best conversion efficiency of the fabricated CZTS film solar cell based on (Cu+Sn)/ZnS precursors was 3.36%.

Cu2ZnSnS4 (CZTS) thin films were grown on Mo-coated Soda-lime-glass (SLG) substrates by sulfurization of sputtered ZnS/Sn/CuS precursors at different temperatures i.e. 560 °C, 580 °C and 600 °C. The effects of sulfurization temperature on the quality of CZTS thin films and solar cells were investigated. The crystal structure, surface morphology, chemical composition, phase purity and surface roughness of CZTS thin films fabricated at different sulfurization temperatures were characterized by X Ray Diffraction (XRD), scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS), Raman spectroscopy and atomic force microscope (AFM), respectively. The results show that all CZTS thin films exhibit a polycrystalline kesterite structure and preferred (112) orientation. For the sulfurization temperature of 580 °C, the obtained CZTS thin films are dense and flat with larger grain size. Meanwhile composition studying indicates that the fabricated CZTS with single phase is copper poor and zinc rich. Furthermore, the surface roughness of CZTS film is the lowest. Finally, the CZTS solar cells with the structure of SLG/Mo/CZTS/CdS/i-ZnO/ITO/Al were fabricated and demonstrated the best power conversion efficiency of 3.59% when used sulfurization temperature was 580 °C.

The influences of sulfurization process on Cu 2 ZnSnS 4 (CZTS) film characters were investigated through soft-annealing and sulfurization precursors, which were prepared by sputtering at room temperature with metal targets and sulfide targets. The Sn-loss of CZTS film was researched by comparing different CZTS films based on metallic precursors and sulfur-contained precursors. As a result, the CZTS film based on metallic precursors showed more serious Sn-loss than that from sulfur-contained precursors. Moreover, the experimental results also demonstrated that an appropriate temperature-time profile during sulfuring process can act as a crucial factor on the morphologies and Sn-loss of CZTS films, and the CZTS films with fine morphologies and appropriate composition were obtained by modifying the time-temperature profile during sulfurization process. Finally, the best solar cell with efficiency of 2.81% was obtained based on the metallic precursor.

Polypropylene (PP) is a kind of semi-crystalline polymer so it is hard to foam with supercritical carbon dioxide (SCCO2). We used polypropylene block (PP-B) copolymer as a modifier to improve the crystallization behaviors and foaming performance of polypropylene homo polymer (HPP). HPP, PP-B, and a series of HPP/PP-B blends were characterized by differential scanning calorimeter (DSC), X-ray diffraction, and polarized optical microscope. Results show that both the crystallization behaviors and melt strength have influence on the cell structure. The crystallization temperature of PP-B is about 7°C higher than that of HPP and that the crystallization behavior of HPP/PP-B blends is similar to that of PP-B. Much denser and smaller size spherulites are observed in PP-B and HPP/PP-B blends than in HPP, and the crystal structure is unchanged after blending. Scanning electron microscope results show that much more uniform, smaller cells can be obtained for the HPP/PP-B blends. The crystal nuclei formed earlier can act as physical cross-link points, increasing the melt strength and improving dramatically the cell structure and morphology of the HPP/PP-B blends. Furthermore, the best cell structure and morphology was achieved for HPP/PP-B blends with the ratio of 70/30 under the same foaming conditions. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers

For hydrogen generation with water splitting, the sluggish reaction kinetics, the scarcity and costliness of the precious-metal catalysts make their practical applications being a big challenge. Herein, heterogeneous catalysts of NiTe@RuO2 and NiTe@NiFe-LDH are constructed by coupling ruthenium oxide (RuO2) and nickel-iron layered double hydroxide (NiFe-LDH) on T-shaped NiTe. The as-made NiTe@RuO2 and NiTe@NiFe-LDH catalysts exhibit outstanding hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activity, respectively. Theoretical calculation and experimental measurement show that the electron transfer at the interface favors the H* adsorption during HER process. We construct full electrochemical cells for overall water splitting using NiTe@RuO2 as the cathode and NiTe@NiFe-LDH as the anode, which delivers a current density of 200 mA cm−2 under a voltage of 1.63 V. When powdered by a solar cell with a voltage of 1.5 V, the full-cell worked well for continuous hydrogen/oxygen generation, showing its potential for sustainable green energy generation.

Exploring high-active catalyst for oxygen evolution reaction (OER) is paramount for efficient and eco-friendly conversion of renewable electricity to hydrogen fuels. In this study, we report a new strategy to significantly enhance the OER activity of Ni3Se4 nanochains via growth of uniformly vertical FeOOH ultrathin nanoneedles on the surface. The as-prepared catalyst demonstrates splendid OER performance with a low overpotential of 249.0 mV for driving a current density of 10 mA cm−2, yielding a small Tafel slope of 46 mV dec−1. After continuous operation of 10 h, a tiny degeneration of 4.0% is afforded, evidencing the excellent durability of the catalyst. On the basis of electrochemical measurement together with theoretical analysis, we attribute the boosted OER kinetics to the synergistic effect of electron, geometry and interface, concretely, two main reasons should be emphasized: 1) the complementary adsorption/desorption nature of nickel and iron leads to optimized Gibbs free energy; 2) redistribution of localized π-symmetry electrons at the interface endows the favorable adsorption/desorption for the oxygenated species. We anticipate that our work would push boundaries for the fabrication of high-performance transition metal- and selenium-based electrocatalysts.

Of the various non-precious catalysts that have been explored thus far, perovskite oxides have attracted much attention due to their intrinsic catalytic activity and structural flexibility. Here we report a new method for enhancing oxygen evolution reation (OER) activity of LaNiO3 perovskite by a thin FeOOH coating. The resulting LaNiO3@FeOOH demonstrates remarkably enhanced OER activity, much better than those of the pristine LaNiO3 or the benchmark RuO2. The excellent OER activity is attributed mainly to the optimized adsorption energy for oxygenated species and fast charge transfer kinetics. Similar enhancement effect of the FeOOH layer is also observed for other perovskite oxides, suggesting that the developed approach could be an effective strategy towards enhancing OER activity of many perovskite catalysts. Moreover, when the LaNiO3@FeOOH is used as the OER catalyst in a rechargeable Zn–air battery, the overpotential of the cell is reduced while maintaining long cycling life, demonstrating the promising prospect for practical applications.

Searching for high-efficient and stable electrocatalyst with low-cost, earth-abundant, and eco-friendly materials are of great interest for the large-scale applications in electrochemical energy systems. Herein, a feasible strategy is developed for boosting the oxygen evolution reaction (OER) kinetics of La0·6Sr0·4Co0·8Fe0·2O3 (LSCF) perovskite oxide by encapsulation of conductive metal-organic frameworks (MOF) of Ni3(HITP)2 on the surface via electrospinning and its further implemented post-annealing treatment. The as-prepared La0·6Sr0·4Co0·8Fe0·2O3@Ni3(HITP)2 (LSCF@Ni3(HITP)2) nanofibers (NFs) exhibits enhanced OER performance and long-term stability towards OER, delivering a low overpotential of 272 mV at 10 mA cm−2 and small Tafel slope as low as 95 mV dec−1. It outperforms the pristine LSCF NFs (345 mV, 188 mV dec−1), bare Ni3(HITP)2 (378 mV, 197 mV dec−1), as well as the state-of-the-art RuO2 (314 mV, 129 mV dec−1). The advanced OER activity is mainly attributable to the synergistic effect of unique 1D (dimensional) NFs structure and the coupled conductive MOF, which endows intrinsic electrical conductivity, fast charge transfer kinetics and favorable mass transportion. Our approach represents a solid step toward exploration of perovskite oxide-based catalysts for high-efficient water oxidation.

Polypropylene (PP) is a kind of semi-crystalline polymer so it is hard to foam with supercritical carbon dioxide (SCCO2). We used hydroxylated multi-walled carbon nanotubes (HO-MWCNTs) as a modifier or nucleator to improve the crystallization behaviors and foaming performance of PP. We prepared the PP/HO-MWCNTs nanocomposite, foamed with SCCO2, and then compared with the pure PP. Results showed that the addition of HO-MWCNTs can make the crystallization type change from homogeneous to heterogeneous nucleation. With the increase of nucleation sites, the nucleation rate increased and the spherulites of the PP/HO-MWCNTs nanocomposite became finer and more uniform. With the formation of an interconnected network in the matrix at an appropriate addition of HO-MWCNT, the tensile strength increased, and the cell of foams was denser and smaller compared with pure PP when foamed with SCCO2 by a high-temperature impregnation method. When the content of HO-MWCNTs reached 1.0 %, the dispersion of HO-MWCNTs in PP matrix is the best and the foaming performance was improved the most significantly. Furthermore, the foaming performance became more stable and the dependence on foaming conditions such as pressure was weakened after addition of HO-MWCNTs.

The scarcity and weak durability of precious metal catalysts are among biggest obstacles to achieving cost-effective electrocatalysts in fuel cells. Hence, it is imperative to develop low-cost non-precious metal catalysts with comparable oxygen reduction reaction (ORR) activity to the precious metal catalysts. Herein, we report a highly effective strategy for facile synthesis of Fe/N-functionalized 3D porous carbon networks. A major advantage of the newly designed catalyst is that ultrafine Fe4N nanoparticles are grown and uniformly mounted on the carbon framework upon pyrolysis treatment at 800 °C, and co-existing with numerous in-situ formed Fe-Nx moieties in the carbon matrix, being evidenced by using X-ray absorption and photoelectron spectroscopy. The new electrocatalysts yield high ORR activity, comparable/superior to that of the state-of-the-art Fe/N-carbon based catalysts reported to date. Specifically, the catalysts show a half-wave potential of 0.890 V and a limited current density of 6.18 mA cm-2, both surpassing the commercial Pt/C. By resorting to the experimental measurements and density-functional theory (DFT) calculations, the synergistic effects between Fe-N4 moieties and the Fe4N support are identified for the first time, which play a key role in boosting catalytic performance of the Fe/N-functionalized porous carbon networks.

Electrocatalysts with outstanding performance have been highly desired toward exploration of new energy storage and conversion devices/systems as well as making an efficient and eco-friendly utilization of green energy. In this study, we composed an iron-based binary diselenide-derived oxide (Fe-SDO) with a facile one-step hydrothermal method to utilize the earth-abundant iron and the probably prosperous catalytic performance of metal-selenides compounds. The catalyst exhibits an overpotential of 226 mV at a current density of 10 mA/cm2, a Tafel slope of 41 mV dec-1, and robust durability after catalyzing vigorous OER for 36 h constantly. Through several analytical methods conducted before and after the oxygen evolution reaction activation on FeSe2 it was discovered that such catalyst possessed a morphology as "Cuju"-like balls with porosity inside in which we explored the vacancy defects and lattice distortion that play significant roles in generating the high electrocatalytic performance of our proposed catalyst by inducing remarkable electron conductivity in the porous Cuju balls (a Chinese traditional football). Throughout our work the superb electrocatalyst performance of the iron-based compounds was demonstrated, and subsequently the underlying reason for such electrocatalyst performance was addressed, which may push boundaries for the exploration of iron-based compounds as OER catalyst and large-scale commercial application of such compounds in the future.

Exploring active, stable, earth-abundant, low-cost, and high-efficiency electrocatalysts is highly desired for large-scale industrial applications toward the low-carbon economy. In this study, we apply a versatile selenizing technology to synthesize Se-enriched Co1–xFexSe2 catalysts on nickel foams for oxygen evolution reactions (OERs) and disclose the relationship between the electronic structures of Co1–xFexSe2 (via regulating the atom ratio of Co/Fe) and their OER performance. Owing to the fact that the electron configuration of the Co1–xFexSe2 compounds can be tuned by the incorporated Fe species (electron transfer and lattice distortion), the catalytic activity can be adjusted according to the Co/Fe ratios in the catalyst. Moreover, the morphology of Co1–xFexSe2 is also verified to strongly depend on the Co/Fe ratios, and the thinner Co0.4Fe0.6Se2 nanosheets are obtained upon selenization treatment, in which it allows more active sites to be exposed to the electrolyte, in turn promoting the OER perfo...

Bimetallic nanoparticles (NPs) have shown amazing charm for their unique structures and catalytic activity. Herein, Au Pd alloy NPs with cuboctahedron structure supported on titanium silicalite-1 (denoted as Au-Pd/TS-1) were prepared by the alcohol reduction method, which exhibited higher gold atom efficiency for the direct propylene epoxidation than the traditional Au/TS-1-DP (prepared by the deposition precipitation method). A combination of experimental characterization with density functional theory (DFT) calculations indicates that the charge transfer from Pd to Au atoms promotes the formation of H2O2 from O2 and H2, and consequently improves the gold atom efficiency of Au-Pd/TS-1 alloy catalysts. The volcano-shaped relationship was established between Pd/Au molar ratio and catalytic activity. Au0.68Pd0.32/TS-1 showed the highest gold atom efficiency of ~1000 gPO h−1 gAu−1 at 200 °C. The insights reported here may pave the way for unraveling the catalyst structure-catalytic activity relationship of supported nano-gold catalysts.

The blisk has been widely used in modern high performance aero-engines of high thrust-weight ratio. Disc milling process provides a reliable way to improve the efficiency of the blisk milling. The process parameters of disc milling have crucial effects on the milling efficiency and physical property of blisk. In this paper, material removal rate, cutter life and thickness of residual stress layer are regarded as optimization targets the key process parameters such as spindle speed, cutting depth and feed speed are optimized. Based on the grey relational analysis, the multi-objective optimization problem is transformed into a single objective optimization problem. At the same time, the problem of non-symmetry influence of key process parameters on optimization targets can be solved. And the influence weight of material removal rate, cutter life and thickness of residual stress layer on the grey relational grade (GRG) are calculated according to principal component analysis. The second order prediction model of GRA is developed by response surface method. On the basis of verifying the accuracy of the model, the influence mechanism of the process parameters coupling on the gray correlation degree is analyzed the optimal process parameter combination is obtained as spindle speed with 81.92 rpm, cutting depth with 5.88 mm and feed rate with 66.0823 mm/min. The experimental research show that the optimal process parameter combination can effectively improve the material removal rate and cutter life and reduce the thickness of residual stress layer.

Tin oxide (SnO2) has been considered as one of the most promising anodes for advanced rechargeable batteries due to its advantages such as high energy density, earth abundance and environmental friendly. However, its large volume change during the Li-Sn/Na-Sn alloying and de-alloying processes will result in a fast capacity degradation over a long term cycling. To solve this issue, in this work we design and synthesize a novel honeycomb-like composite composing of carbon encapsulated SnO2 nanospheres embedded in carbon film by using dual templates of SiO2 and NaCl. Using these composites as anodes both in lithium ion batteries and sodium-ion batteries, no discernable capacity degradation is observed over hundreds of long term cycles at both low current density (100 mA g(-1)) and high current density (500 mA g(-1)). Such a good cyclic stability and high delivered capacity have been attributed to the high conductivity of the supported carbon film and hollow encapsulated carbon shells, which not only provide enough space to accommodate the volume expansion but also prevent further aggregation of SnO2 nanoparticles upon cycling. By engineering electrodes of accommodating high volume expansion, we demonstrate a prototype to achieve high performance batteries, especially high-power batteries. (C) 2017 Elsevier B.V. All rights reserved. Funding Agencies|National Natural Science Foundation of China (NSFC) [51502099, 51571096, 61405026]; Natural Science Foundation of Hubei Province [2016CFB129]; Fundamental Research Funds for the Central Universities [HUST: 2016YXMS211]; Swedish Research Councils [Vetenskapsradet: 621-2014-5461, Formas: 2016-00559]; Aforsk foundation [16399]

CoPt/Ag nanocomposite films have been prepared by magnetron sputtering and subsequent annealing. The effect of Ag on the structure and magnetic properties of CoPt/Ag nanocomposite films was investigated. It was found that the existence of the Ag plays a dominant role in inducing the (001) texture of the film. (001) textured CoPt/Ag nanocomposite films with a large perpendicular coercivity in the range of 5.6–7.0 kOe have been achieved after annealing at 600 °C. The Cu additive is very effective to reduce the ordering temperature in CoPtAg system. With Cu additive, the CoPtCuAg films start ordering at a lower annealing temperature of 450 °C, which is lower by 150 °C than the pure CoPtAg films.