The formation of dendrites on a zinc (Zn) metal anode has limited its practical applications on aqueous batteries. Herein, an artificial composite protective layer consisting of nanosized metal–organic frameworks (MOFs) to improve the poor wetting effect of aqueous electrolytes on the Zn anode is proposed to reconstruct the Zn/electrolyte interface. In this layer, hydrophilic MOF nanoparticles serve as interconnecting electrolyte reservoirs enabling nanolevel wetting effect as well as regulating an electrolyte flux on Zn anode. This zincophilic interface exhibits significantly reduced charge-transfer resistance. As a result, stable and dendrite-free Zn plating/stripping cycling performance is achieved for over 500 cycles. In addition, especially at higher C-rates, the coating layer significantly reduces the overpotentials in a Zn/MnO2 aqueous battery during cycling. The proposed principle and method in this work demonstrate an effective way to reconstruct a stable interface on metal anodes (e.g., Zn) where a conventional solid-electrolyte interface (SEI) cannot be formed.

Enhancing the efficiency of non-noble electrocatalysts in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) for water splitting remains a challenging task. Herein, we report an electronic push/pull effect of Co and Fe doping on the HER and OER performance of Ni-based hydroxides as revealed by thorough cyclic voltammetry and X-ray photoelectron spectroscopy analysis. A Fe dopant pulls partial electrons from nearby Ni/Co active sites resulting in a higher electron affinity at the Ni/Co sites to facilitate OH– adsorption and charge transfer from the adsorbed OH– for OER. In contrast, a Co dopant tends to push its partial electrons to nearby Ni sites and increase the number of lattice O2– as proton adsorption sites, which lead to faster charge transfer for HER. By adjusting the contents of Co/Fe dopants in Ni-based hydroxides, we were able to tune the electronic configuration of the catalyst and to optimize the OER and HER performance specifically. An optimized catalyst with a composition of Ni0.8Co0.1Fe0.1O x H y showed excellent OER performance with an overpotential (η) of 239 mV at 10 mA·cm–2 and a Tafel slope of 45.4 mV·dec–1. The HER performance was optimized with a catalyst composition of Ni0.9Co0.1O x H y and reached an η of 85 mV at 10 mA·cm–2 and a Tafel slope of 84.5 mV·dec–1. Overall water splitting with Ni0.8Co0.1Fe0.1O x H y as the anode and Ni0.9Co0.1O x H y as the cathode was demonstrated at a low potential of 1.58 V at 10 mA·cm–2. Utilizing the electronic push/pull effect by dopant elements provides a new pathway for the design and optimization of the transition hydroxides as HER and OER catalysts.

Intervertebral disc degeneration (IDD) is a common degenerative disease of the musculoskeletal system and is also the main cause of chronic low back pain (LBP), which seriously affects the quality of life of patients and places a huge economic burden on families and society. [1][2][3] It is estimated that about 20% of adolescents have mild IDD and 80% of the general population will experience back pain symptoms during their lifetime. 4 However, the specific pathogenesis of IDD is still not fully understood. At present, IDD is believed to be a complex cell-mediated process that ultimately leads to changes in intervertebral disc (IVD) structure and function. 5

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Wheat and maize are two major food crops in China. Conventional fertilizer recommendations result in higher than necessary costs to farmers and increased environmental pollution. It is essential to quantitatively estimate optimal fertilizer requirements to alleviate the problems of the two crops in China. The QUEFTS (QUantitative Evaluation of the Fertility of Tropical Soils) model was used to estimate region-specific nitrogen (N), phosphorus (P) and potassium (K) requirements as well as fertilizer applications needed to realize target yields of wheat and maize. Data of field experiments with different fertilization treatments of various regions in China during the years of 1985 -1995 were used to calibrate the QUEFTS model for both wheat and maize. Minimum and maximum internal nutrient efficiencies (kg grain kg )1 ) for the model were estimated at N (25 and 56), P (171 and 367), K (24 and 67) for wheat, and N (21 and 64), P (126 and 384), K (20 and 90) for maize. The model suggested a linear increase of grain yields for scenarios with nutrient contents of 24.6, 3.7 and 23.0 kg N, P and K per 1000 kg of wheat grain and 25.8, 4.3 and 23.1 kg N, P and K per 1000 kg of maize grain. These results suggest that the average N: P: K ratio in the plant dry matter is about 6.7: 1: 6.2 for wheat and 6.0: 1: 5.4 for maize. Relationships between internal N, P and K levels and soil properties were established and relationships between the recovery efficiencies of applied fertilizer -N, P and K were found. Running the calibrated QUEFTS model with observed field data produced a good fit between predicted and observed data. It was concluded that the calibrated QUEFTS model could be a useful tool for improving fertilizer recommendations for wheat and maize in China.

Molybdenum disulfide, as an electronic highly-adjustable catalysts material, tuning its electronic structure is crucial to enhance its intrinsic hydrogen evolution reaction (HER) activity. Nevertheless, there are yet huge challenges to the understanding and regulation of the surface electronic structure of molybdenum disulfide-based catalysts. Here we address these challenges by tuning its electronic structure of phase modulation synergistic with interfacial chemistry and defects from phosphorus or sulfur implantation, and we then successfully design and synthesize electrocatalysts with the multi-heterojunction interfaces (e.g., 1T0.81-MoS2@Ni2P), demonstrating superior HER activities and good stabilities with a small overpotentials of 38.9 and 95 mV at 10 mA/cm2, a low Tafel slopes of 41 and 42 mV/dec in acidic as well as alkaline surroundings, outperforming commercial Pt/C catalyst and other reported Mo-based catalysts. Theoretical calculation verified that the incorporation of metallic-phase and intrinsic HER-active Ni-based materials into molybdenum disulfide could effectively regulate its electronic structure for making the bandgap narrower. Additionally, X-ray absorption spectroscopy indicate that reduced nickel possesses empty orbitals, which is helpful for additional H binding ability. All these factors can decrease Mo-H bond strength, greatly improving the HER catalytic activity of these materials.

No abstract

Black phosphorus (BP) has recently attracted significant interest due to its unique electronic and optical properties. Doping is an effective strategy to tune a material's electronic structures, however, the direct and controllable growth of BP with a high yield and its doping remain a great challenge. Here we report an efficient short-distance transport (SDT) growth approach and achieve the controlled growth of high quality BP with the highest yield so far, where 98% of the red phosphorus is converted to BP. The doping of BP by As, Sb, Bi, Se and Te are also achieved by this SDT growth approach. Spectroscopic results show that doping systematically changes its electronic structures including band gap, work function, and energy band position. As a result, we have found that the air-stability of doped BP samples (Sb and Te-doped BP) improves compared with pristine BP, due to the downshift of the conduction band minimum with doping. This work develops a new method to grow BP and doped BP with tunable electronic structures and improved stability, and should extend the uses of these class of materials in various areas.