Highly active iron-nitrogen-boron-carbon bifunctional electrocatalytic platform for hydrogen peroxide sensing and oxygen reduction

Mechanistic insight into confined Fenton system in the MXene layer (MXene-Fe@PES) for enhanced aquatic contaminant removal

The confinement strategy was considered as an effective method for enhanced aquatic contaminant removal in catalytic systems, and the two-dimensional (2D) material displayed sufficient capacities for contaminant attenuation as compared to other materials due to the unique interlayer structures. However, information on the construction of confined catalytic systems using 2D materials is still lacked. Here, a novel 2D catalytic system in which Fe atoms were illustrated into MXene layers and polyether sulfone (PES) substrate (named MXene-Fe@PES) was established to explore its degradation potential toward typical aquatic contaminants e.g., phenol. Compared to the control (Fe@PES), higher electron densities and migration rates, but lower coordination numbers of Fe atoms were achieved in the MXene-Fe@PES system. This new system with 14.5 Å channels (model phenol: 1.472 s-1) exhibited an ultrafast degradation rate, which was 60∼1200 times higher than the common homogeneous and heterogeneous Fenton-like systems. Further analysis showed that enhanced reactive oxygen species generation, electron density of Fe site, H2O2 decomposition, electron interactions between Fe and H2O2, and O-O bond cleavage in H2O2 accounted for the improved contaminant removal. Moreover, the degradation pathway of phenol was changed from the kinetically favorable ring-opening pathway in Fe@PES system to the thermodynamically favorable oligomerization pathway in MXene-Fe@PES system. Application in actual water samples, including river waters, lake waters, and treated-wastewater effluents showed that the removal efficiencies were maintained at 69∼97%, indicating high potential for water decontamination. Correlation analysis showed that phenol removal in actual waters was negatively correlated with the abundances and molecular weights of dissolved organic matters as well as the phosphorus concentrations. This study provides not only a paradigm for the delicate design of high-efficient confined Fenton reaction system, but also a theoretical reference for the construction and selection of catalytic systems in environment restoration of actual waters.

Methyl esters synthesis from Luffa cylindrica seeds oil using green copper oxide nanoparticle catalyst in membrane reactor

This study investigates the potential role of Juglans sp. root extract-mediated copper oxide nanoparticles of Luffa cylindrica seed oil (LCSO) into methyl esters. The synthesized green nanoparticle was characterized by Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), and Scanning electron microscopy (SEM) spectroscopies to find out the crystalline size (40 nm), surface morphology (rod shape), particle size (80-85 nm), and chemical composition (Cu = 80.25% & O = 19.75%), accordingly. The optimized protocol for the transesterification reaction was adjusted as oil to methanol molar ratio (1:7), copper oxide nano-catalyst concentration (0.2 wt %), and temperature (90 °C) corresponding to the maximum methyl esters yield of 95%. The synthesized methyl esters were characterized by GC-MS, 1H NMR, 13C NMR, and FT-IR studies to know and identify the chemical composition of newly synthesized Lufa biodiesel. The fuel properties of Luffa cylindrica seed oil biofuel were checked and compared with the American Biodiesel standards (ASTM) (D6751-10). Finally, it is commendable to use biodiesel made from wild, uncultivated, and non-edible Lufa cylindrica to promote and adopt a cleaner and sustainable energy method. The acceptance and implementation of the green energy method may result in favourable environmental effects, which in turn may lead to better societal and economic development.

Designing Oxide Catalysts for Oxygen Electrocatalysis: Insights from Mechanism to Application

The electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are fundamental processes in a range of energy conversion devices such as fuel cells and metal-air batteries. ORR and OER both have significant activation barriers, which severely limit the overall performance of energy conversion devices that utilize ORR/OER. Meanwhile, ORR is another very important electrochemical reaction involving oxygen that has been widely investigated. ORR occurs in aqueous solutions via two pathways: the direct 4-electron reduction or 2-electron reduction pathways from O2 to water (H2O) or from O2 to hydrogen peroxide (H2O2). Noble metal electrocatalysts are often used to catalyze OER and ORR, despite the fact that noble metal electrocatalysts have certain intrinsic limitations, such as low storage. Thus, it is urgent to develop more active and stable low-cost electrocatalysts, especially for severe environments (e.g., acidic media). Theoretically, an ideal oxygen electrocatalyst should provide adequate binding to oxygen species. Transition metals not belonging to the platinum group metal-based oxides are a low-cost substance that could give a d orbital for oxygen species binding. As a result, transition metal oxides are regarded as a substitute for typical precious metal oxygen electrocatalysts. However, the development of oxide catalysts for oxygen reduction and oxygen evolution reactions still faces significant challenges, e.g., catalytic activity, stability, cost, and reaction mechanism. We discuss the fundamental principles underlying the design of oxide catalysts, including the influence of crystal structure, and electronic structure on their performance. We also discuss the challenges associated with developing oxide catalysts and the potential strategies to overcome these challenges.

The Biomass of Pig-Blood-Derived Carbon as a Novel Electrode Material for Hydrogen Peroxide Electrochemical Sensing

In the work, a pig-blood-derived mesoporous carbon (BC) was prepared as a novel Fe-N-C material for the electrochemical sensor to detect hydrogen peroxide. Because of the unique nanostructure of Fe-BCs with rough surface structure, hierarchical pores, and high graphitization degree, the Fe-BCs, as a kind of advanced electrode material, exhibited remarkable performance in electrocatalysis. The sensor based on Fe-BCs exhibited an extra-long range from c and a detection limit of 0.046 μM (S/N = 3). The synthesis of low-cost, advanced carbon-based electrode materials from environmentally friendly pig blood for electrochemical sensor construction is a promising approach.

Investigation on the evolution of hydrothermal biochar

The objective of this study was to visualize trends and current research status of hydrothermal biochar research through a bibliometric analysis by using CiteSpace software. The original article data were collected from the Web of Science core database published between 2009 and 2020. A visual analysis network of national co-authored, institutional co-authored and author co-authored articles was created, countries, institutions and authors were classified accordingly. By visualizing the cited literature and journal co-citation networks, the main subject distribution and core journals were identified respectively. By visualizing journal co-citations, the main research content was identified. Further the cluster analysis revealed the key research directions of knowledge structure. Keyword co-occurrence analysis and key occurrence analysis demonstrate current research hotspots and new research frontiers. Through the above analysis, the cooperation and contributions of hydrothermal biochar research at different levels, from researchers to institutions to countries to macro levels, were explored, the disciplinary areas of knowledge and major knowledge sources of hydrothermal biochar were discovered, and the development lineage, current status, hotspots and trends of hydrothermal biochar were clarified. The results obtained from the study can provide a reference for scholars to gain a deeper understanding of hydrothermal biochar.

Rational design of mixed ionic-electronic conducting membranes for oxygen transport

The mixed ionic-electronic conducting (MIEC) oxides have generated significant research efforts in the scientific community during the last 40 years. Since then, many MIEC compounds, most of which are based on perovskite oxides, have been synthesized and characterized. These compounds, when heated to high temperatures, form solid ceramic membranes with high oxygen ionic and electrical conductivity. The driving force for oxygen ion transport is the ionic transfer of oxygen from the air as a result of the differential partial pressure of oxygen across the membrane. Electronic and ionic transport in a range of MIEC materials has been studied using the defect theory, particularly when dopants are introduced to the compound of interest. As a result, many types of ionic oxygen transport limits exist, each with a distinct phase shift depending on the temperature and partial pressure of oxygen in use. In combination with theoretical principles, this work attempts to evaluate the research community's major and meaningful achievements in this subject throughout the preceding four decades.

Heavy metals pollution characteristics and risk assessment in sediments and waters: The case of Tianjin, China

Potential health and ecological risks due to heavy metal pollution in surface waters and sediments were evaluated based on a health risk assessment model and a potential ecological risk index method. Combined with the reclamation progress of Tianjin Nangang Industrial Zone, in China, a survey was carried out in the area dealing with heavy metals concentrations in surface waters and sediments, covering from 2008 to 2018. Specifically, concentrations were determined for As, Cd, Hg, Cu, Pb, and Zn. The results show that As、Cd、Hg、Cu 、Pb、Zn average concentrations in surface water were 0.99 μg/L∼1.27 μg/L, 0.13 μg/L∼0.63 μg/L, 0.03 μg/L∼0.13 μg/L, 1.5 μg/L∼4.65 μg/L, 1.25 μg/L∼4.7 μg/L, 13.5 μg/L∼20.99 μg/L and which average concentrations in sediment were 5.12 mg/kg∼12.34 mg/kg, 0.12 mg/kg∼0.18 mg/kg, 0.04 mg/kg ∼0.087 mg/kg, 13.45 mg/kg∼31.92 mg/kg, 13.2 mg/kg ∼21.26 mg/kg, 21.58 mg/kg ∼77.21 mg/kg, respectively. The background values of the Hailuan River basin near the study area were taken as the reference and compared with the national sediment quality standards a tell us the quality of the sediments in Tianjin Nangang coastal area being good. As regards the characteristics of pollution, heavy metals showed a high concentration in 2008 and then decreased significantly, which related to the dredging of large amounts of contaminated surface sediment during port construction. According to the phase equilibrium partition coefficient (Kp) and temporal and spatial distribution characteristics of heavy metals, sediments can be seen as an obvious sink for lead, with this element being mainly affected by exogenous input in coastal seawater. Zn, As, Cd, and Hg contents in surface water were greatly affected by the endogenous release from sediments. The results of the environmental risk assessment showed that the main environmental health risk of Tianjin coastal waters was carcinogenic, and specifically due to As. The potential heavy metals ecological risk assessment results of surface sediments were mild for the affected areas.

Pt/Pd Decorate MOFs Derived Co-N-C Materials as High-Performance Catalysts for Oxygen Reduction Reaction

We report here, a strategy to prepare Pt/Pd nanoparticles decorated with Co-N-C materials, where Co-N-C was obtained via pyrolysis of ZIF-67 directly. As-prepared Pt/Pd/Co-N-C catalysts showed excellent ORR performance, offered with a higher limit current density (6.6 mA cm−2) and similar half-wave potential positive (E1/2 = 0.84 V) compared with commercial Pt/C. In addition to an ORR activity, it also exhibits robust durability. The current density of Pt/Pd/Co-N-C decreased by only 9% after adding methanol, and a 10% current density loss was obtained after continuous testing at 36,000 s.

Perovskite oxide for emerging photo(electro)catalysis in energy and environment

Using solar energy to catalyse photo-driven processes to address the energy crisis and environmental pollution plays a role in the path to a sustainable society. Many oxide-based materials, especially perovskite oxides, have been widely investigated as catalysts for photocatalysis in energy and environment because of the low-cost and earth-abundant and good performance. At this stage, there is a need to present a scientific-based evaluation of the technologies developed so far and identify the most sustainable technologies and the existing limitations and opportunities for their commercialisation. This work comprehensively investigated the outcomes using various scientometric indices on perovskite oxide-based photo(electro)catalysts for water splitting, nitrogen fixation, carbon dioxide conversion, organic pollutant degradation, current trends and advances in the field. According to the results achieved, efforts in both energy and environment based on perovskite oxides have been initiated in the 1990s and accelerated since the 2010s. China and the United States were identified as the most contributing countries. Based on the results achieved in this study, the main milestones and current trends in the development of this field have been identified. The aim of this research is to provide useful guidelines for the further investigation of perovskite oxide-based catalysts for photoelectrocatalysis and photocatalysis both in energy and environment on the applications such as water splitting, nitrogen fixation, carbon dioxide conversion, and wastewater treatment.

Biomass-derived N,S co-doped 3D multichannel carbon supported Au@Pd@Pt catalysts for oxygen reduction

A beancurd-derived mesoporous carbon (NSC) was prepared by an environmentally friendly procedure, and then it was investigated as Au@Pd@Pt core-shell catalysts support (Au@Pd@Pt-NSC) for oxygen reduction reaction (ORR). The Au@Pd@Pt-NSC (E_1/2 = 0.91 V) has a marginally negative ORR half-wave potential compared with other materials, in particular Pt/C (E_1/2 = 0.87 V) and Au@Pd@Pt-C (E_1/2 = 0.81 V). The specific and mass activities of the Au@Pd@Pt-NSC were 5 and 13 times higher than the commercial a Pt/C catalyst. After 20000 cycles of rapid durability test, the Au@Pd@Pt-NSC sample showed a loss of just 4.9% compared with the initial ECSA area, which can be attributed to the favorable interaction between Au@Pd@Pt and NSC. These results can be considered of environmental relevance and high potential applicability.

New research on water, waste and energy management, with special focus on antibiotics and priority pollutants

The Editors of the Virtual Special Issue (VSI) "New Research on Water, Waste and Energy Management, with Special Focus on Antibiotics and Priority Pollutants" (VSI WWEM-20) here present details corresponding to papers that have been accepted, as well as further comments on the matter. It should be noted that the VSI should be associated to a Conference that had been initially programmed to be held in Rome during the summer of 2020, Unfortunately, it was postponed due to the COVID-19 pandemic. That conference was one of those within the series called "International Congress on Water, Waste and Energy Management". Although the Conference was postponed, the Call for Papers for the VSI was maintained by this journal. As a result, a set of very interesting papers were accepted after a careful peer-review process. We hope that it will be complemented with additional VSIs associated to future conferences corresponding to the series, increasing the knowledge on the topic.