Atomically thin two-dimensional (2D) van der Waals materials have exhibited many exotic layer-dependent physical properties including electronic structure, magnetic order, etc. Here, we report a striking even-odd layer dependent oscillation...
2D ferroelectrics with robust polar order in the atomic‐scale thickness at room temperature are needed to miniaturize ferroelectric devices and tackle challenges imposed by traditional ferroelectrics. These materials usually have polar point group structure regarding as a prerequisite of ferroelectricity. Yet, to introduce polar structure into otherwise nonpolar 2D materials for producing ferroelectricity remains a challenge. Here, by combining first‐principles calculations and experimental studies, it is reported that the native Ga vacancy‐defects located in the asymmetrical sites in cubic defective semiconductor α‑Ga2Se3 can induce polar structure. Meanwhile, the induced polarization can be switched in a moderate energy barrier. The switched polarization is observed in 2D α‑Ga2Se3 nanoflakes of ≈4 nm with a high switching temperature up to 450 K. Such polarization switching could arise from the displacement of Ga vacancy between neighboring asymmetrical sites by applying an electric field. This work removes the point group limit for ferroelectricity, expanding the range of 2D ferroelectrics into the native defective semiconductors.
In this manuscript, N-doped porous
carbonaceous CO2 sorbents
were synthesized using biomass waste hazelnut shell as the raw materials,
melamine as the nitridation agent, and KOH as the porogen. The resultant
materials were carefully characterized by different techniques, and
the results show that these samples possess a high amount of N content
and highly developed porous structure. As a result, high CO2 adsorption capacities were found for this series of sorbents, up
to 4.23 and 6.34 mmol/g at 1 bar and 25 and 0 °C, respectively.
Comprehensive investigation indicates that, in addition to the well-known
narrow microporosity and N content, the pore size distribution of
the adsorbent also plays an important role in dictating the CO2 uptake under ambient conditions. Thus, it is proposed that
the joint effect of the above three factors dictates the CO2 adsorption capacity of these sorbents. Moreover, these sorbents
exhibit many other exceptional CO2 adsorption properties,
such as stable recyclability, fast adsorption kinetics, suitable heat
of adsorption, high CO2/N2 selectivity, and
good dynamic CO2 capture capacity. The wide availability
and low cost of raw materials together with a straightforward synthesis
procedure and excellent performance disclose the high potential of
hazelnut-shell-derived carbons in CO2 capture.
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