Effect of internal migration on the environment in China

We examine the effect of inter-provincial migration on air and water pollution for a panel of Chinese provinces over the period 2000–2013. To do so, we employ linear and non-linear panel data models in a Stochastic Impacts by Regression on Population, Affluence and Technology (STIRPAT) framework. Results from linear and non-linear models suggest that inter-provincial migration has contributed to pollution. Second-generation linear panel data model results suggest that for every additional 10,000 inter-provincial migrants, chemical oxygen demand (COD) increases 0.27–0.58%, sulphur dioxide (SO₂) increases 0.08–0.25% and aggregate waste disposed (WST) increases 0.04–0.26%. Non-linear threshold panel model results suggest that for every additional 10,000 inter-provincial migrants, COD increases 0.2–0.5%, SO₂ increases 0.10–0.20% and WST increases 3.1–4.2%.     

Uniform nitrogen and sulfur co-doped carbon nanospheres as catalysts for the oxygen reduction reaction

Uniform nitrogen and sulfur co-doped carbon nanospheres with an average diameter of approximately 200 nm were prepared using sulfur and polyacrylonitrile as precursors. The materials were characterized using scanning electron microscopy, transmission electron microscopy, elemental analysis, and X-ray photoelectron spectroscopy. The characterization results suggest the as-prepared materials had uniform, porous, nanospherical morphologies and high surface areas. For the typical sample containing 9.5% sulfur, the surface area is up to 653 m² g⁻¹. The catalysts exhibited enhanced catalytic activity, outstanding long-term stability, and excellent methanol tolerance in an alkaline medium. Significantly, the sulfur addition was found to be vital in improving materials’ catalytic performance through preventing aggregation of the nanospheres, constructing porous structures, increasing the surface area, and participating in the formation of active sites.     

Hydrogen production and End-Uses from combined heat,hydrogen and power system by using local resources

To address the problem of fossil fuel usage at the Missouri University of Science and Technology campus, using of alternative fuels and renewable energy sources can lower energy consumption and hydrogen use. Biogas, produced by anaerobic digestion of wastewater, organic waste, agricultural waste, industrial waste, and animal by-products is a potential source of renewable energy. In this work, we have discussed Hydrogen production and End-Uses from CHHP system for the campus using local resources. Following the resource assessment study, the team selects FuelCell Energy DFC1500™ unit as a molten carbonate fuel cell to study of combined heat, hydrogen and power (CHHP) system based on a molten carbonate fuel cell fed by biogas produced by anaerobic digestion. The CHHP system provides approximately 650 kg/day. The total hydrogen usage 123 kg/day on the university campus including personal transportation applications, backup power applications, portable power applications, and other mobility applications are 56, 16, 29, 17, and 5 respectively. The excess hydrogen could be sold to a gas retailer. In conclusion, the CHHP system will be able to reduce fossil fuel usage, greenhouse gas emissions and hydrogen generated is used to power different applications on the university campus.     

Energy recovery from microalgal biomass via enhanced thermo-chemical process

This work showed that microalgae having low lipid content has high potential for energy recovery via thermo-chemical processes. As an example, Microcystis aeruginosa (M. aeruginosa) was considered and tested. Specifically, this work verified that the growth rate of M. aeruginosa was extremely fast compared to other microalgae (as a factor of ∼10). Moreover, this work investigated the CO₂ co-feed impact on thermo-chemical processes (pyrolysis/gasification) using M. aeruginosa. Introducing CO₂ in the thermo-chemical process as reaction media or feedstock can enhance the efficiency of thermo-chemical processes by expediting the cracking capability of condensable hydrocarbons (tar). The generation of CO was enhanced as a factor of ∼2. Further generation of H₂ could be achieved in the presence of CO₂. Thus, utilizing CO₂ as reaction media or chemical feedstock can modify the end products into environmentally benign and desirable ones. The CO₂ co-feed impact on thermo-chemical processes with lingo-cellulosic biomass can be universally applied.     

Additively manufactured 316L stainless steel: An efficient electrocatalyst

In the quest of finding an economical, yet efficient material, the idea of fabricating 316L stainless steel using additive manufacturing technology was explored to produce material with refined sub-granular structure. The surface of the stainless steel was further chemically treated with an etching solution to expose the grain boundaries. The grain boundary enriched surface resulted in more active sites for the oxygen evolution reaction (OER) in additively manufactured treated (AM-T) 316L stainless steel. AM-T sample manifests enhanced catalytic activity for OER with an overpotential of 310 mV to draw a 10 mA/cm² current density, along with a lower Tafel slope of 42 mV/dec compared to AM and wrought samples. These features were validated from the increased double-layer capacitance of AM-T and approximately 1.5 times larger electrochemically effective surface area of AM-T due to etching treatment compared to the wrought sample. Furthermore, AM-T also possesses stable activity retention for 100 h at a current density of 10 mA/cm².     

Avoidance of partial load operation at coal-fired power plants by storing nuclear power through power to gas

The need of fast regulation of electricity production leads to a number of inconveniences occurred to the electric generation system and the electric market, especially to the nuclear power. A new concept to control nuclear power production is posed in order to allow the regulation of the electricity sent to the grid. This concept proposes the joint operation of a nuclear power plant, a coal power plant with postcombustion capture and a methanation plant. The cost effectiveness of this technology and its capability to reduce the CO₂ emissions -consumed in the methanation process- are assessed through the design and economic and environmental analysis of a hybrid facility. Mainly due to the increase of the operating hours of the coal-fired power plant, the environmental feasibility of the initial proposal seems to be limited. However, given that benefits are expected in the medium and long-term (2020–2030) for the Power to Gas facility, a future alternative use is proposed. The target of this new alternative configuration will be the storage of CO₂ together with the storage of renewable energy.     

Photodeposited CoOx as highly active phases to boost water oxidation on BiVO4/WO3 photoanode

Surface decoration of photoanodes with oxygen evolution cocatalysts is an efficient approach to improve the photoelectrochemical water splitting performance. Herein, ultrafine CoO_x was selectively immobilized on the surface of BiVO₄/WO₃ photoanode by using the photogenerated holes to in-situ oxidize Co₄O₄ cubane. The composited photoanode (CoO_x/BiVO₄/WO₃) displayed an enhanced photoelectrochemical (PEC) water oxidation performance, with a photocurrent density of 2.3 mA/cm² at 1.23 V_RHE under the simulated sunlight irradiation, which was 2 times higher than that of bare BiVO₄/WO₃. The characterization results for the morphological, optical and electrochemical properties of the photoelectrodes revealed that, the enhanced PEC performances could be attributed to the improved charge carrier separation/transport behaviors and the promoted water oxidation kinetics when the photoelectrodes were loaded with CoO_x.     

A facile synthesis of nano-layer structured g-C3N4 with efficient organic degradation and hydrogen evolution using a MDN energetic material as the starting precursor

The construction of a high-performance g-C₃N₄ photocatalyst through a facile and green synthesis method remains a great challenge for H₂ production and organic pollutants degradation. In this work, we developed a nano-layer structured g-C₃N₄ (NL-CN) photocatalyst with a 230 m²/g surface area via the thermal polymerization method using melaminium dinitrate (MDN), which is one of the more energetic materials, as the precursor. The energy coming from the drastic decomposition of nitrate anions in MDN caused the thick layers of bulk CN to be exfoliated to produce many much-thinner nano-layers when at 500 °C for 2 h, which obviously elevated the surface area of the g-C₃N₄. The resultant NL-CN displays a superior visible-light H₂-generation and rhodamine B (RhB) photodegradation efficiency (λ > 420 nm) compared to those of bulk g-C₃N₄ (CN) prepared through heating melamine because of the nano-layered structures, which lead to higher specific surface areas, a rapid charge transfer efficiency and a higher redox potential. These results demonstrate that the utilization of MDN as a starting material provides a new opportunity for the facile and green synthesis of high-efficiency nanostructured g-C₃N₄ photocatalysts with lower energy consumption and environmental pollution levels.     

Ordered mesoporous Ni/Silica-carbon as an efficient and stable catalyst for CO2 reforming of methane

Ordered mesoporous silica-carbon (MSC) were used as supports of Ni based catalysts for dry reforming of methane (DRM) reaction. The effects of preparation method and precipitant on the catalysts are investigated. The physical and chemical properties are discussed based on the H₂-TPR, FTIR, XRD, TEM, H₂-TPD and N₂ adsorption/desorption characterization. It is found that the preparation method and choice of precipitants affect the catalysts significantly in terms of the properties and catalytic performance in DRM reaction. In detail, the catalysts prepared by the precipitation method show more highly dispersed Ni particles and further better catalytic activity than the impregnated catalyst. That is attributed to the forming Ni₃Si₂O₅(OH)₄ nanoflakes in the catalyst precursors with the existence of alkaline precipitants. And this Ni₃Si₂O₅(OH)₄ species bind the support more tightly than NiO in the impregnated Ni/MSC catalyst. Moreover, the choice of precipitants also influences the form of Ni₃Si₂O₅(OH)₄ species in the catalysts. Specially, the strong electrolytic capacity of NaOH gives the most Ni₃Si₂O₅(OH)₄ nanoflakes formed in Ni-MSC-1 catalyst, which results in the most highly Ni dispersity and further highest catalytic activity. Besides, the strong interaction between the Ni₃Si₂O₅(OH)₄ species and support are also advantageous to the resist sintering and formation of carbon deposition, that is related to the good catalytic stability of catalysts.     

Bioaugmentation with Thermoanaerobacterium thermosaccharolyticum W16 to enhance thermophilic hydrogen production using corn stover hydrolysate

In the present work, with corn stover hydrolysate as the substrate, an efficient hydrogen-producing thermophile, Thermoanaerobacterium thermosaccharolyticum W16, was added to three kinds of seed sludge (rotten corn stover (RCS), cow dung compost (CDC), and sludge from anaerobic digestion (SAD)) to investigate the effect of bioaugmentation on thermophilic hydrogen production. Batch test results indicate that the bioaugmentation with a small amount of the strain T. thermosaccharolyticum W16 (5% of total microbes) increased the hydrogen yield to varying degrees (RCS: from 8.78 to 9.90 mmol H₂/g utilized sugar; CDC: from 8.18 to 8.42 mmol H₂/g utilized sugar; SAD: from 8.55 to 9.17 mmol H₂/g utilized sugar). The bioaugmentation process also influenced the soluble metabolites composition towards more acetate and less butyrate production for RCS, and more acetate and less ethanol accumulation for SAD. Microbial community analysis indicates that Thermoanaerobacterium spp. and Clostridium spp. dominated microbial community in all situations and might be mainly responsible for thermophilic hydrogen generation. For RCS and SAD, the bioaugmentation obviously increased the relative abundance of the strain T. thermosaccharolyticum W16 in microbial community, which might be the main reason for the improvement of hydrogen production in these cases.