Metal-organic frameworks (MOFs) have recently emerged as a type of uniformly and periodically atom-distributed precursor and efficient self-sacrificial template to fabricate hierarchical porous-carbon-related nanostructured functional materials. For the first time, a Cu-based MOF, i.e., Cu-NPMOF is used, whose linkers contain nitrogen and phosphorus heteroatoms, as a single precursor and template to prepare novel Cu P nanoparticles (NPs) coated by a N,P-codoped carbon shell that is extended to a hierarchical porous carbon matrix with identical uniform N and P doping (termed Cu P@NPPC) as an electrocatalyst. Cu P@NPPC demonstrates outstanding activity for both the hydrogen evolution and oxygen reduction reaction, representing the first example of a Cu P-based bifunctional catalyst for energy-conversion reactions. The high performances are ascribed to the high specific surface area, the synergistic effects of the Cu P NPs with intrinsic activity, the protection of the carbon shell, and the hierarchical porous carbon matrix doped by multiheteroatoms. This strategy of using a diverse MOF as a structural and compositional material to create a new multifunctional composite/hybrid may expand the opportunities to explore highly efficient and robust non-noble-metal catalysts for energy-conversion reactions.
Photodetectors
are one of the most important components for a future
“Internet-of-Things” information society. Compared to
the mainstream semiconductor-based photodetectors, emerging devices
based on two-dimensional (2D) materials and ferroelectrics as well
as their hybrid systems have been extensively studied in recent decades
due to their outstanding performances and related interesting physical,
electrical, and optoelectronic phenomena. In this paper, we review
the photodetection based on 2D materials and ferroelectric hybrid
systems. The fundamentals of 2D and ferroelectric materials as well
as the interaction in the hybrid system will be introduced. Ferroelectricity
modulated optoelectronic properties in the hybrid system will be discussed
in detail. After the basics and figures of merit of photodetectors
are summarized, the 2D-ferroelectrics devices with different structures
including p-n diodes, Schottky diodes, and field-effect
transistors will be reviewed and compared. The polarization of ferroelectrics
offers the possibility of the modulation and enhancement of the photodetection
in the hybrid detectors, which will be discussed in depth. Finally,
the challenges and perspectives of the photodetectors based on 2D
ferroelectrics will be proposed. This Review outlines the important
aspects of the recent development of the hybrid system of 2D and ferroelectric
materials, which could interact with each other and thus lead to photodetectors
with higher performances. Such a Review will be helpful for the research
of emerging physical phenomena and for the design of multifunctional
nanoscale electronic and optoelectronic devices.
Designing a tailor-made MOF to prepare Co9S8 embedded in N, O and S-tridoped carbon nanomaterials, which has a highly efficient electrocatalytic oxygen reaction activity.
The direct synthesis is the most promising alternative method for the production of hydrogen peroxide, and the bottleneck is still unsolved. The breakthrough lies in elusive reaction mechanism issues. In this work, advanced coverage-dependent kinetic modeling is combined with the energetics from firstprinciples calculations to investigate the formation of H 2 O 2 over transition metals. We show that the adsorbate−adsorbate interactions considerably affect the reaction mechanism of synthesis of hydrogen peroxide on Pd(111). Without the coverage effect, O 2 is likely to go through the direct dissociation mechanism, and water is the major product. When the coverage effects are included, the dissociations of O−O and O−OH bonds are significantly inhibited, and on the contrary, the hydrogenations of O 2 and OOH are promoted, leading to the production of H 2 O 2 . We demonstrate that the reaction temperature induces strong variations in the coverage of intermediates, which in turn causes changes in product selectivity. Being consistent with the operando experiment, our kinetic simulations indicate that the H 2 /O 2 partial pressure ratio has great effects on H 2 O 2 selectivity and the reaction rate of H 2 O 2 is lower under hydrogen-rich (oxygen-lean) and oxygen-rich (hydrogen-lean) conditions, which is highly related to the intermediate coverage. The same approach is also applied to other important relevant metals, i.e., Cu(111), Au(111), PdAu, and PdHg alloys, and the trends of activity and selectivity have been obtained.
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