RESUMEN
The polymorphism of phosphorus-based materials has garnered much research interest, and the variable chemical bonding structures give rise to a variety of micro and nanostructures. Among the different types of materials containing phosphorus, elemental phosphorus materials (EPMs) constitute the foundation for the synthesis of related compounds. EPMs are experiencing a renaissance in the post-graphene era, thanks to recent advancements in the scaling-down of black phosphorus, amorphous red phosphorus, violet phosphorus, and fibrous phosphorus and consequently, diverse classes of low-dimensional sheets, ribbons, and dots of EPMs with intriguing properties have been produced. The nanostructured EPMs featuring tunable bandgaps, moderate carrier mobility, and excellent optical absorption have shown great potential in energy conversion, energy storage, and environmental remediation. It is thus important to have a good understanding of the differences and interrelationships among diverse EPMs, their intrinsic physical and chemical properties, the synthesis of specific structures, and the selection of suitable nanostructures of EPMs for particular applications. In this comprehensive review, we aim to provide an in-depth analysis and discussion of the fundamental physicochemical properties, synthesis, and applications of EPMs in the areas of energy conversion, energy storage, and environmental remediation. Our evaluations are based on recent literature on well-established phosphorus allotropes and theoretical predictions of new EPMs. The objective of this review is to enhance our comprehension of the characteristics of EPMs, keep abreast of recent advances, and provide guidance for future research of EPMs in the fields of chemistry and materials science.
RESUMEN
The wettability of molten carbonate on carbon determines the electrochemical performances of high-temperature direct carbon fuel cells (DCFCs). However, a universal method to measure the high-temperature wettability of molten carbonate is absent and the wetting kinetics is not well understood. Herein, we develop a dispensed drop (DD) method to measure the wetting kinetics of molten carbonate (Li2CO3-Na2CO3-K2CO3, 43.5:31.5:25.0, molar ratio) on the carbon substrate at 450-750 °C under controlled atmospheres (100%Ar, 100%CO2, and 1%O2-99%N2). The measured contact angles under different conditions reveal that increasing the O2- concentration in the gas-liquid-solid (GLS) interface decreases the contact angle. In addition, elevating the temperature, introducing O2 in the gas atmosphere, or pretreating the carbon substrate can enhance the wetting kinetics of molten carbonates. The molten carbonate completely wets the carbon substrate in 150 min in Ar gas atmosphere and in 30 min in 1%O2-99%N2 gas atmosphere at 600 °C. Further, it takes only 30 min to completely wet the pretreated carbon substrate in Ar atmosphere at 600 °C. Overall, this paper offers the DD method to study the wettability of molten carbonate on the carbon substrate, which is helpful to understand the underlying wetting mechanism and engineer the electrode design for DCFCs.
RESUMEN
The multi-anion molybdenum-based nanohybrids, N-doped ß-Mo2C/MoP/MoOx (denoted as MoCPO), serving as a highly efficient catalyst for hydrogen evolution reaction (HER), are fabricated via a simple and scalable electrosynthesis in molten NaCl-KCl, which integrates pyrolysis/electroreduction/compounding into a one-pot strategy using polyphosphazenes (PPAs) and earth-abundant molybdenite (mainly MoS2) as precursors. The deliberately selected PPA and molten electrolyte ensure the unique lamellar nanostructures and the blending of multiple anions of C, N, P, and O in the obtained catalyst, specifically, triggering the in situ formation of the structural oxygen vacancies (VO) in MoCPO. The nature of the hybrids can be regulated by adjusting the synthesis condition. The optimized hybrid displays a low overpotential of 99.2 mV at 10 mA cm-2 for HER in 0.5 M H2SO4 and stays active over a broad pH range. The theoretical calculations reveal that VO in the hybrids serves as favorable active sites, thus contributing to the superior HER activity. Moreover, MoCPO is also effective for overall water splitting as a bifunctional catalyst.
RESUMEN
Converting CO2 into value-added chemical fuels and functional materials by CO2 reduction reaction (CO2RR) is conducive to achieving a carbon-neutral energy cycle. However, it is still challenging to efficiently navigate CO2RR toward desirable products. Herein, we report a facile strategy to extend product species in borate-containing molten electrolyte at a positively shifted cathodic potential with a high current density (e.g. 100 mA/cm2), which can selectively electro-transform CO2 into desired products (either CO or solid carbon nanofibers, respectively reaching a high selectivity of â¼90%). The borates can act as a controller of electrolyte alkalinity to buffer the concentration of sequentially generated O2- during CO2RR, positively shifting the reduction potential of the captured CO2 and concurrently extending the product species. The sustainable buffering effect is available under CO2 atmosphere. Compared with borate-free electrolyte, the CO2 conversion efficiency is over three times higher, while the electrolysis energy consumption is decreased by over 40%.
