Magnetic hierarchically porous biomass carbon for realizing broadband and strong absorption of electromagnetic wave

Hierarchically porous carbon materials provide favorable conditions for electromagnetic wave loss enhancement due to the superimposed positive influence of multilevel pores. However, high production costs and complex preparation limit their large-scale production. Biomass carbon with a natural hierarchically porous structure offers an alternative; however, the impedance mismatch and single-loss mechanism prevent biomass carbon from being an ideal absorbent for broadband and strong absorption. In this study, a series of magnetic hierarchically porous biomass carbons were prepared using a facile adsorption-inert calcination method. The natural hierarchical porous structure of the loofah sponge provides numerous adsorption sites for ferric ions, which are transformed in situ into Fe₃O₄ during calcination to regulate the conductivity. The impedance matching and electromagnetic loss properties of the biomass carbon/Fe₃O₄ composites were adjusted by varying the amount of ferric nitrate. Optimal performance occurs when ferric nitrate weighs 0.8 g, and the calcination temperature is 600 °C. Under these conditions, the effective absorption bandwidth reaches 5.28 GHz (11.84–17.12 GHz, 2.5 mm), and the minimum reflection loss (RL_min) is as low as −52.54 dB (4.5 mm), which is achieved by superior impedance matching and strong conduction loss together with polarization loss due heterogeneous interfaces and carbon defects. Our work provides a new perspective and a simple method for the large-scale production of high-efficiency biomass-based electromagnetic wave absorbents.     

A novel approach to synthesizing highly active Ni2P/SiO2 hydrotreating catalysts

Silica-supported nickel phosphide particles with high dispersion were obtained by treating nickel metal particles on a support with 10% PH₃/H₂. Because the phosphidation occurred at relatively low temperature, the small nickel phosphide particles had the same size as the metal particles, and this size was maintained. The resulting catalysts were characterized by CO and O₂ chemisorption, XRD, and ³¹P MAS NMR spectroscopy. The influence of the nickel source on the metal dispersion of the catalysts was investigated. The resulting silica-supported nickel phosphide catalysts proved to be very active in the hydrodesulfurization of dibenzothiophene and the hydrodenitrogenation of o-methylaniline in the presence and absence of H₂S.     

Impact of distributed generation on protection of single wire earth return lines

Distributed generation (DG) inclusion within the grid system potentially introduces problems related to control, protection, harmonics, and network transients. This paper analyses one of the key issues: protection of the network, by ascertaining the impact of rotary DG inclusion on existing protection system of SWER (single wire earth return) lines and the DG sensitivity during faults. The analysis is carried out by estimating fault-sensitivity for the worst-case situation, determining the DG impact on the existing protection scheme, and comparing the network situation with and without DG during the fault. A model of arc voltage is used to represent a fault on a SWER scheme. The size of DG is selected based on the SWER capacity and SWER load. The study is conducted on an example SWER system by considering the SWER lines with and without DG and faults on the SWER backbone and laterals, and simulation results are reported. In every case studied, the fault current from the DG significantly exceeded the DG rating and the DG would have tripped. Thus the system reverts to the case with no DG. Even if DG did not trip, the fault current from the source would be largely independent of the DG, and thus the original feeder protection would continue to provide the same quality of performance. Hence, net sensitivity and existing protection system will not be adversely affected by DG inclusion in SWER lines.     

Photo-electrochemical hydrogen generation from water using solar energy. Materials-related aspects

The present work considers hydrogen generation from water using solar energy. The work is focused on the materials-related issues in the development of high-efficiency photo-electrochemical cells (PECs). The property requirements for photo-electrodes, in terms of semiconducting and electrochemical properties and their impact on the performance of PECs, are outlined. Different types of PECs are overviewed and the impact of the PEC structure and materials selection on the conversion efficiency of solar energy are considered.Trends in research in the development of high-efficiency PECs are discussed. It is argued that very sophisticated materials engineering must be used for processing the materials that will satisfy the specific requirements for photo-electrodes. An important issue in the processing of these materials is the bulk vs. interface properties at the solid/solid interfaces (e.g., grain boundaries) and solid/liquid interfaces (e.g., electrode/electrolyte interface). Consequently, the development of PECs with the efficiency required for commercialization requires the application of up-to-date materials processing technology.The performance of PECs is considered in terms of:

• •excitation of electron–hole pair in photo-electrodes;
• •charge separation in photo-electrodes;
• •electrode processes and related charge transfer within PECs;
• •generation of the PEC voltage required for water decomposition.

This work also gives empirical data on the performance of PECs of different structures and materials selection.It is argued that PEC technology is the most promising technology for hydrogen production owing to several reasons:

• •PEC technology is based on solar energy, which is a perpetual source of energy, and water, which is a renewable resource;
• •PEC technology is environmentally safe, with no undesirable byproducts;
• •PEC technology may be used on both large and small scales;
• •PEC technology is relatively uncomplicated.

According to current predictions, the production of hydrogen will skyrocket by 2010 (Morgan and Sissine, Congressional Research Service, Report for Congress. The Committee for the National Institute for the Environment, Washington, DC, 20006-1401, 28 April 1995). Consequently, seed funding already has been allocated to several national research programs aiming at the development of hydrogen technology. The countries having access to this PEC technology are likely to form the OPEC of the future.     

Preparation of magnetic polymeric composite nanoparticles by seeded emulsion polymerization

Seeded emulsion polymerization was used to prepare magnetic polymeric composite nanoparticles (MPCNPs) with the aim to successfully encapsulate magnetite particles and to improve particle size distribution (PSD). Microscopical morphology and number-average diameter of hydrophilic magnetite particles (HMPs), magnetic seed latex nanoparticles (MSLNPs) and MPCNPs were observed and analyzed by transmission electron microscope (TEM). Weight-average diameter and PSD of MSLNPs and MPCNPs were also analyzed by TEM. Magnetic properties of MPCNPs were investigated by Vibrating Sample Magnetometry (VSM). The results showed that the encapsulation of magnetite particles was not complete by conventional emulsion polymerization but very successful by seeded emulsion polymerization, the resulted MPCNPs were nanoparticles with much narrower PSD than that of MSLNPs, and exhibited superparamagnetism and possessed a certain level of magnetic response.     

Pt–Cu Interaction Induced Construction of Single Pt Sites for Synchronous Electron Capture and Transfer in Photocatalysis

Single-atom photocatalysts have shown their fascinating strengths in enhancing charge transfer dynamics; however, rationally designing coordination sites by metal doping to stabilize isolated atoms is still challenging. Here, a one-unit-cell ZnIn₂S₄ (ZIS) nanosheet with abundant Cu dopants serving as the suitable support to achieve a single atom Pt catalyst (Pt₁/Cu–ZIS) is reported, and hence the metal single atom–metal dopant interaction at an atomic level is disclosed. Experimental results and density functional theory calculations highlight the unique stabilizing effect (Pt–Cu interaction) of single Pt atoms in Cu-doped ZIS, while apparent Pt clusters are observed in pristine ZIS. Specifically, Pt–Cu interaction provides an extra coordination site except three S sites on the surface, which induces a higher diffusion barrier and makes the single atom more stable on the surface. Apart from stabilizing Pt single atoms, Pt–Cu interaction also serves as the efficient channel to transfer electrons from Cu trap states to Pt active sites, thereby enhancing the charge separation and transfer efficiency. Remarkably, the Pt₁/Cu–ZIS exhibits a superb activity, giving a photocatalytic hydrogen evolution rate of 5.02 mmol g⁻¹ h⁻¹, nearly 49 times higher than that of pristine ZIS.     

Study on the photocatalytic property of La-doped CoO/SrTiO3 for water decomposition to hydrogen

The purpose of this study is to investigate the effect of La doping on the photocatalytic property of CoO/SrTiO₃. The experimental results show that a suitable concentration of La doping greatly improved the photocatalytic activity of CoO/SrTiO₃. The activity first increased, reached a maximum, and then decreased drastically with increasing doping concentration. The physical properties of the catalyst were characterized using XRD, SEM and UV-visible diffuse reflectance spectra. The influence of loading amount of co-catalyst CoO on the photocatalytic activity of La-doped SrTiO₃ was also studied and it was found that the optimum loading amount increased with increasing doping concentration.     

Correction to: Application of a Bayesian Watershed Model Linking Multivariate Statistical Analysis to Support Watershed-Scale Nitrogen Management in China

Water Resources Management - Unfortunately in the original version of this article, the Electronic Supplementary Material was unintentionally omitted during the publishing process     

Noble metal-free bimetallic NiCo decorated Zn0.5Cd0.5S solid solution for enhanced photocatalytic H2 evolution under visible light

As we know, noble metal (Pt, Pd and Au) with appropriate adsorption free energy of H atoms and higher work function as cocatalyst has been considered to be an effective tactic to enhance photocatalytic activity. However, they are limited severely by scarcity and high-cost. Herein, Zn_0.5Cd_0.5S solid-solution photocatalyst decorated with noble metal-free NiCo cocatalyst has been successfully obtained through one-step photochemical route. It is found that the lifespan of charge carriers of Zn_0.5Cd_0.5S@NiCo can be prolonged dramatically after modification, and the photocatalytic H₂ rate reach to 34.7  mmol g⁻¹·h⁻¹ is nearly 9 times higher than the bare Zn_0.5Cd_0.5S (λ ≥ 420 nm). The superior photocatalytic activity for ZCS@NiCo could be mainly ascribed to higher separation and transfer efficiency of photogenerated carriers by introduced bimetallic NiCo cocatalysts possessing the superior electron transfer property and reducing the onset over-potential of water reduction, which was proved by experiment. This study can provide a potential strategy to design a more efficient noble metal-free cocatalyst over photocatalyst.