Three-stage integration system with solid oxide fuel cell, alkali metal thermal electric converter and organic Rankine cycle for synergistic power generation

During operation, solid oxide fuel cell releases quite a great part of hydrogen energy into waste heat, leading to energy waste and even functional component degradation. In this study, solid oxide fuel cell, alkali metal thermal electric converter and organic Rankine cycle are synergistically integrated as a three-stage integration system to gradually and efficiently utilize the waste heat. Accounting a variety of thermodynamic-electrochemical losses within the system, mathematical expressions of power output, energy efficiency, exergy destruction rate, and exergy efficiency for the integration system are deduced. The basic performance features and competitiveness of the integration system are revealed. The maximum power output density of the proposed system allows to be 12407.0 W m−2, which is approximately improved by 103.8 % compared to that of the stand-alone solid oxide fuel cell (6087.4 W m−2). Parametric studies demonstrate that an increase in operation temperature, operation pressure or radiation loss geometric factor enhances the integration system performance, while an increase in β″-alumina solid electrolyte thickness, proportional coefficient or pinch temperature ratio degrades the integration system performance. The results obtained can provide some theoretical support for designing or running such an actual three-stage integration system for efficient power generation

Enhancing Hydrogen Peroxide Synthesis through Coordination Engineering of Single-Atom Catalysts in the Oxygen Reduction Reaction: A Review

Hydrogen peroxide (H2O2) is an important chemical with a diverse array of applications. However, the existing scenario of centralized high-concentration production is in contrast with the demand for low-concentration decentralized production. In this context, the on-site green and efficient two-electron oxygen reduction reaction (ORR) for H2O2 production has developed into a promising synthetic approach. The development of low-cost, highly active, and durable advanced catalysts is the core requirement for realizing this approach. In recent years, single-atom catalysts (SACs) have become a research hotspot owing to their maximum atom utilization efficiency, tunable electronic structure, and exceptional catalytic performance. The coordination engineering of SACs is one of the key strategies to unlock their full potential for electrocatalytic H2O2 synthesis and holds significant research value. Despite considerable efforts, precisely controlling the electronic structure of active sites in SACs remains challenging. Therefore, this review summarizes the latest progress in coordination engineering strategies for SACs, aiming to elucidate the relevance between structure and performance. Our goal is to provide valuable guidance and insights to aid in the design and development of high-performance SACs for electrocatalytic H2O2 synthesis

Effects of Physical Forcing on Summertime Hypoxia and Oxygen Dynamics in the Pearl River Estuary

A validated hydrodynamic-biogeochemical model was applied to investigate the effects of physical forcing (i.e., river discharge, winds, and tides) on the summertime dissolved oxygen (DO) dynamics and hypoxia (DO < 3 mg L−1) in the Pearl River estuary (PRE), based on a suite of model sensitivity experiments. Compared with the base model run in 2006 (a wet year), the simulated hypoxic area in the moderate year (with 75% of river discharge of the base run) and the dry year scenario (with 50% of river discharge of the base run) was reduced by ~30% and ~60%, respectively. This is because under the lower river discharge levels, less particulate organic matter was delivered to the estuary that subsequently alleviated the oxygen demand at the water–sediment interface, and in the meantime, the water stratification strength was decreased, which facilitated the vertical diffusion of DO. Regarding the effect of winds, the highly varying and intermittent strong winds had a significant impact on the replenishment of bottom DO by disrupting water stratification and thus inhibiting the development of hypoxia. Sensitivity experiments showed that the hypoxic area and volume were both remarkably increased in the low wind scenario (with a bottom hypoxic zone extending from the Modaomen sub-estuary to the western shoal in Lingdingyang Bay), whereas hypoxia was almost absent in the strong wind scenario. The DO budget indicated that winds altered the bottom DO mostly by affecting the DO flux due to vertical diffusion and horizontal advection, and had a limited influence on the DO consumption processes. Moreover, the DO concentration exhibited remarkable fluctuations over the spring-neap tidal cycles due to the significant differences in vertical diffusion. The results of a tide-sensitivity experiment indicated that without tide forcing, most of the shallow areas (average water depth < 5 m) in the PRE experienced severe and persistent hypoxia. The tides mainly enhanced mixing in the shallow areas, which led to higher vertical diffusion and enhanced replenishment of bottom DO

A revised phylogeny of holarctic treefrogs (Genus Hyla) based on nuclear and mitochondrial DNA sequences

The treefrog genus Hyla (Anura: Hylidae) consists of at least 31 species found in North America, Central America, Europe, and Asia and is the only genus of hylids that occurs outside the New World. Despite intensive work on the phylogeny of the genus in the past few years, several problems still exist regarding relationships within Hyla. These problems include the unusual placements of H. gratiosa and H. walkeri in some recent studies and the relatively limited taxon sampling of Asian species. In the present study, we revisit the phylogeny of Hyla to address some of these problems. First, we tested the unexpected placements of H. gratiosa and H. walkeri by sampling additional individuals of these species. Our results show that the unusual placements of H. gratiosa and H. walkeri in previous studies were most likely due to a mislabelled tissue sample and a misidentified specimen, respectively. Second, we included two species of Asian Hyla not included in previous phylogenies. Our study provides additional evidence for two separate colonizations of Hyla from the New World into Asia, and suggests an unusual biogeographic pattern in the Asian Hyla clades

Sintering Process and Effects on LST and LST-GDC Particles Simulated by Molecular Dynamics Modeling Method

During development of substitute anode materials suitable for solid oxide fuel cell (SOFC), understanding of sintering mechanisms and effects is significant for synthesized porous structures and performance. A molecular dynamics (MD) model is developed and applied in this study for the SOFC anode sintered materials to reveal the sintering condition effects. It is predicted that, for the case of two nanoparticles of electron-conducting La-doped SrTiO3 (LST), the higher the sintering temperature, the faster the aggregation of nanoparticles and the higher the sintering degree. An increase in the nanoparticle size could delay the sintering, process but does not affect the final sintering degree. The MD model is further applied for the case of the multi-nanoparticles containing LST and ion-conducting electrolyte materials of gadolinium-doped ceria (GDC), i.e., the LST-GDC particles. The sintering conditions and effects on the LST-GDC particles are evaluated, in terms of the mean square displacement (MSD) and various structural parameters. Two important thermal properties are also calculated that agree well with the experimental values. The findings obtained from this study are useful to identify the optimized sintering parameters for development of the SOFC electrode materials

Surface-growing organophosphorus layer on layered double hydroxides enables boosted and durable electrochemical freshwater/seawater oxidation

Developing high-efficiency and cost-effective electrocatalysts for oxygen evolution reaction (OER) is crucial for hydrogen production from electrolysis. Herein, a facile and universal strategy for fabricating organophosphorus (OP) layer encapsulated layered double hydroxide (LDH) is proposed for robust freshwater/seawater oxidation. This approach is based on a self-growing strategy using phytic acid (PA) to realize superb OER activity due to the electron transfer from metal ions in LDH to the phosphate groups in the OP layer. The phosphate group enriched OP layer can also efficiently avoid chloride corrosion via “physical blocking” and “electrostatic repelling”, enabling the OP-NiCo-LDH catalyst to show durable seawater oxidation catalysis performance. It requires an overpotential of 330 mV to deliver a 500 mA cm-2 seawater oxidation with excellent durability for 500 h. Moreover, only 1.59 V is required to achieve a 500 mA cm-2 overall seawater splitting for OP-NiCo-LDH||NiMoN cell. The refore, this work provides a strategy to design robust OER catalysts for industrial water/seawater electrolysis