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Due to the environmental deterioration caused by modern industrialization, the key focus of researchers worldwide is diverted toward clean and sustainable energy sources, such as fuel cells and metal-air batteries, where the oxygen reduction reaction (ORR) at the cathode plays a central role. Unfortunately, the sluggish kinetics at the cathode of the ORR, in which the platinum-based (Pt-based) catalyst plays a critical role, is the principal impediment to commercialization. Pt and Pt-based, cutting-edge ORR electrocatalysts suffer from high cost, low methanol tolerance, and poor stability. Researchers have made tremendous efforts towards substitution of Pt-based catalysts, and significant achievements were accomplished in the form of alternatives such as metal oxides, nitrides, chalcogenides, carbides, metal-free nanocarbon, and metal-nitrogen/carbon (M-N/C) nanocomposites. Among these innumerable substitutes of Pt-based catalysts, M-N/C shows great potential because of their high stability, high methanol tolerance, and admirable ORR activities. In this review, we have summarized the principles and factors determining the rate of ORR, which are related to different surface planes of the crystal, surface area, and electronic structure tunability, where the morphology, multiple heteroatom-doping, and controlled particle size play a vital role. Furthermore, we have also discussed the synthetic protocol of different ORR materials such as Pt-based, metal chalcogenides, metal oxides, and M-N/C nanocomposites and the challenges related to these materials. Hopefully, this review will provide a status update as well as new directions to the scientific community engaged in designing novel catalytic materials for energy and environmental applications.

Lithium–selenium (Li–Se) batteries suffer from the problems of polyselenides dissolution and volume expansion of active materials during the charge/discharge process. Moreover, the heavy atomic mass of selenium atoms limits the capacitive property of a Li–Se battery. Porous materials as the host for selenium particles reported by previous research studies are often disordered in pore structure and nonuniform in pore size. Herein, we report that a three-dimensional (3D) nitrogen-doped carbon photonic crystal (NCPC) with an ordered, interconnected structure was synthesized via a simple method to be the host of active materials. In addition, we prepared a Se-rich Se1–xSxby introducing a small amount of sulfur into a selenium ring to reduce the molecular mass but still keep the high electronic conductivity. As cathodes for a Li–Se battery, amorphous Se-rich Se1–xSx@NCPC composites exhibited high electrochemical performance with a specific capacity of 692 mA h g–1at 0.1 Ag1–, an excellent rate capability of 526 mA h g–1at 3 Ag1–, and an outstanding cycling property with an ultralow decay rate of 0.0132% per cycle at 0.6 Ag1–over 1000 cycles. Moreover, the pouch cell of Se1–xSx@NCPC composites also showed a good property with an energy of 253 Wh kg–1at 0.1 Ag1–and an outstanding rate energy of 192 Wh kg–1at 1.5 Ag1–, manifesting great potential in practical application.

With the advancement in nanotechnology, we are experiencing transformation in world order with deep insemination of nanoproducts from basic necessities to advanced electronics, health care products and medicines. Therefore, nanoproducts, however, can have negative side effects and must be strictly monitored to avoid negative outcomes. Future toxicity and safety challenges regarding nanomaterial incorporation into consumer products, including rapid addition of nanomaterials with diverse functionalities and attributes, highlight the limitations of traditional safety evaluation tools. Currently, artificial intelligence and machine learning algorithms are envisioned for enhancing and improving the nano-bio-interaction simulation and modeling, and they extend to the post-marketing surveillance of nanomaterials in the real world. Thus, hyphenation of machine learning with biology and nanomaterials could provide exclusive insights into the perturbations of delicate biological functions after integration with nanomaterials. In this review, we discuss the potential of combining integrative omics with machine learning in profiling nanomaterial safety and risk assessment and provide guidance for regulatory authorities as well.

The remediation of wastewater containing Pb2+has attracted much attention due to the harm of Pb2+to the environment and human health. A promising adsorbent, functionalized montmorillonite modified with a ligand diethylenetriamine (DETA) was prepared under mild reaction conditions. The modified montmorillonite (DETA-MMT) and nature montmorillonite (Na-MMT) were then characterized with the help of XRD, FTIR, TG/DTG, and BET. It was revealed that the modifier DETA was successfully inserted into interlayers of montmorillonite, as demonstrated by the characterizations. Batch adsorption experiments of Pb2+onto Na-MMT and DETA-MMT in solutions were studied as a function of various parameters, such as pH, contact time, initial concentration, and temperature. The maximum adsorption capacity of DETA-MMT was 61.1 mg g–1, which had more than doubled compared with that of Na-MMT. The adsorption thermodynamics of Pb2+by DETA-MMT was studied, and it showed a endothermic process. The adsorption kinetics of two samples both fit well with the pseudo-second-order model. The adsorption isotherms of Na-MMT and DETA-MMT can be well described by the Langmuir isotherm and Freundlich isotherm, respectively. Furthermore, the adsorbed Pb2+onto DETA-MMT can hardly be dissolved under weak acidic condition (pH >4) according to the desorption experiments of simulated acid rain and Tessier’s sequential extraction procedure.

For the first time we have successfully constructed semi conductive copper–biphenylamines framework hybrid photocatalysts to degrade organic pollutants. Cu complexes sensitized photocatalysts of g-C3N4, i.e.CN-Cu(BN), CN-Cu(PD) and CN-Cu(BA), have been successfully tested for photocatalytic degradation of organic pollutants under visible light illumination, and a significant enhancement in catalytic activity was observed for CN-Cu(BA) in comparison to pristine g-C3N4. The modified material creates a charge separation with the electrons populating the higher CB and the holes the lower VB, thus enhancing the redox reaction power of the charge carriers. CN-Cu (BA) can easily degrade 99% of RhB in 1.5 hours and 60% of phenol in 2 hours. While the degradation efficiency of CN-Cu(BN), CN-Cu(PD) and g-C3N4is lower than that of CN-Cu(BA). The kobsfor CN-Cu(BN) is 0.01985 min−1, 5.2 times higher than that of g-C3N4, and that of CN-Cu(BA) is 0.0292 min−1which is 7.55 times greater than that of pristine g-C3N4. These degradation outcomes are favourable for developing a modified catalyst in bulk amount and its application. The strong holes can directly degrade RhB and phenol. Promoting the injection of electrons from g-C3N4into the copper unit as well as strengthening the electronic interactions between the two units enhanced its activity.

Constructing a stable non-dendritic lithium metal anode is the key to the development of high-energy batteries in the future. Herein, we fabricated nitrogen-doped carbon photonic crystals in situ in the macropores of carbon papers as a porous skeleton and confined hosts for metallic lithium. The large specific surface area of the carbon photonic crystal reduces the current density of the electrode. The three-dimensional ordered microstructure promotes uniform charge distribution and uniform lithium deposition and inhibits the volume expansion of metallic lithium. The as-prepared lithium metal anode exhibits prominent electrochemical performance with a small hysteresis of less than 95 mV beyond 180 cycles at an extremely high current density of 15 mA cm–2. When the as-prepared lithium metal anode is coupled with the sulfur cathode, the obtained full cell displays enhanced capacitive properties and cycle life. Compared with the bare Li anode, the full cell exhibits more than 300 cycles of cell life and a 70 mA h g–1higher discharge capacity.