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SnSb2Te4 (SST), a ternary van der Waals (vdW) material, has been widely investigated during last decades for potential applications in superconductivity, thermoelectricity, and optoelectronics. Recently, atomically thin SST has been predicted to show abnormal electronic band structure evolutions, high carrier mobility, and strong light–matter interaction. However, controllable synthesis of such SST crystals has been a huge challenge. Herein, atomically thin SST flakes are prepared via a chemical vapor deposition (CVD) method by using SbCl3, SnCl4·5H2O, and Te as the precursors. Multiple structural characterizations reveal that the SST flakes are single crystals with high crystallinity. Due to the narrow bandgap of 0.42 eV, SST‐based photodetectors have a broadband spectrum detection range from visible light through communication bands (480–1550 nm). More importantly, benefiting from a high room‐temperature carrier mobility over 300 cm2 V−1 s−1, the SST photodetectors demonstrate a response/recovery time of tens of tens of microseconds, which exceeds most typical transition metal dichalcogenide (TMDC) flakes. In addition, the photodetector maintains high performance after being exposed to the air for 2 months, suggesting good environmental stability. These excellent performances suggest that the SST flakes are promising for next‐generation optoelectronics. [ABSTRACT FROM AUTHOR]

Using electrochemical CO2 reduction reaction (CO2RR) to synthesize value-added hydrocarbons provides a useful solution for environmental issues and energy crisis. However, this process is impeded by the low activity and selectivity of electrocatalysts toward targeted products. Employing density functional theory computations, the graphdiyne and holey graphyne supported single-atom catalysts (SACs, M/GDY and M/HGY) are demonstrated to be the promising candidates for the CO2RR. By taking full elemental diversity of metal sites across the periodic table, 25 catalysts are found to effectively activate CO2 and inhibit competitive hydrogen evolution, and 8 of them show higher activity for CH4 production than Cu(211). Remarkably, changing supports are found to greatly affect limiting potentials and reaction pathways, even leading to an "inert-active" transition for some metal centers. The resulting SACs, including Mn/GDY, Co/HGY, Ru/GDY, and Os/GDY, can achieve high activity with low limiting potentials of " -0.22 to -0.58 V. Machine learning enables to identify the critical role of the polarized charge and magnetic moment of metal atoms in affecting the activity. The built machine learning model also shows an interpretable capability to predict the activity of the other types of SACs, offering a great promise to quick screening of high-performance SACs. [ABSTRACT FROM AUTHOR]

The potential‐driven semiconductor‐to‐metal transition is investigated in monolayer transition metal dichalcogenides by employing a new proposed method, i.e., the fixed‐potential method (FPM). Under the same voltage, the semiconducting and metallic phases will be charged differently due to their different electronic properties. The potential‐driven phase transition process is simulated by the injection of unequal electrons in the semiconducting and metallic phases. The unequal electron injection is more consistent with the actual experimental process, although equal electron injection also can theoretically induce a phase transition. MoTe2 is chosen as a prototypical example to examine the physical mechanism. When the fixed electrode potential is above the potential of zero‐charge, excess electrons are injected into the metallic 1T' phase instead of the semiconducting 2H phase, stabilizing the 1T' phase. In addition, the potential‐dependent kinetics, in which the charge transfer is fluctuating, suggests that increasing the electrode potential will decrease the kinetic barrier of the 2H→1T' transition process. The calculated relative transition voltage of 2.5 V agrees well with the experimental results, demonstrating the validity of the FPM. This study provides new insight into potential‐driven semiconductor‐to‐metal phase transitions and suggests a new theoretical approach for studies under constant voltage conditions. [ABSTRACT FROM AUTHOR]

To achieve efficient ammonia synthesis via electrochemical nitrogen reduction reaction (NRR), a qualified catalyst should have both high specific activity and large active surface area. However, integrating these two merits into one single material remains a big challenge due to the difficulty in balancing multiple reaction intermediates. Here, it is demonstrated that the boron‐analogues of MXenes, namely "MBenes", could cope with the challenge and achieve the high activity and large reaction region simultaneously toward NRR. Using extensive density functional theory computations and taking 16 MBenes as representatives, it is identified that seven MBenes (CrB, MoB, WB, Mo2B, V3B4, CrMnB2, and CrFeB2) not only have intrinsic basal plane activity for NRR with limiting potentials ranging from −0.22 to −0.82 V, but also possess superior capability of suppressing the competitive hydrogen evolution reaction. Particularly, different from the MXenes whose surface oxidation may block the active sites, once oxidized, these MBenes can catalyze NRR via the self‐activating process, reducing O*/OH* into H2O* under reaction conditions, and favoring the N2 electroreduction. As a result, the exceptional activity and selectivity, high active area (≈1019 m−2), and antioxidation nature render these MBenes as pH‐universal catalysts for NH3 production without introducing any dopants and defects. [ABSTRACT FROM AUTHOR]

Recently, Kovalenko and co-workers and Li and co-workers developed CsPbX3 (X = Cl, Br, I) inorganic perovskite quantum dots (IPQDs), which exhibited ultrahigh photoluminescence (PL) quantum yields (QYs), low-threshold lasing, and multicolor electroluminescence. However, the usual synthesis needs high temperature, inert gas protection, and localized injection operation, which are severely against applications. Moreover, the so unexpectedly high QYs are very confusing. Here, for the first time, the IPQDs' room-temperature (RT) synthesis, superior PL, underlying origins and potentials in lighting and displays are reported. The synthesis is designed according to supersaturated recrystallization (SR), which is operated at RT, within few seconds, free from inert gas and injection operation. Although formed at RT, IPQDs' PLs have QYs of 80%, 95%, 70%, and FWHMs of 35, 20, and 18 nm for red, green, and blue emissions. As to the origins, the observed 40 meV exciton binding energy, halogen self-passivation effect, and CsPbX3@X quantum-well band alignment are proposed to guarantee the excitons generation and high-rate radiative recombination at RT. Moreover, such superior optical merits endow them with promising potentials in lighting and displays, which are primarily demonstrated by the white light-emitting diodes with tunable color temperature and wide color gamut. [ABSTRACT FROM AUTHOR]

A high-performance Schottky sensor boosted by interface modulation is fabricated for the detection of trace nitro-explosives vapors. The interface modulation strategy results in a silicon nanowires (SiNWs) array/TiO2/reduced graphene oxide (rGO) sensor with sensitive and selective response toward nitro-explosives vapors. The response of the SiNWs array/TiO2/rGO sensor toward nitro-explosives vapors, such as 9 ppb 2,4,6-trinitrotoluene, 4.9 ppt hexogen, and 0.25 ppq octagon, is boosted by 2.4, 7.5, and 5 times with the insertion of TiO2. Superior selectivity is shown even compared with interfering gases of 10 ppm. Such good sensing performance can be attributed to the good sensing performance of the Schottky heterojunction-based sensor, the Schottky barrier height modulation with the insertion of TiO2, SiNWs array structure enhanced diffusion, and TiO2 nanoparticles enhanced adsorption. This is believed to be the first Schottky heterojunction-based sensor for nitro-explosives vapors detection. This work would open a new way to develop highly sensitive and selective sensors. [ABSTRACT FROM AUTHOR]

Simultaneously improving activity and stability is a crucial yet challenge in the development of metallic single‐atom‐based catalysts. In current work, a novel approach is introduced to address this issue by combining post‐adsorption and secondary pyrolysis techniques to create a synergistic catalytic system, in which the single atoms (SAs) Fe sites played in the NC matrix (Fe─NC) are coupled with high‐entropy atomic clusters (HEACs). Theoretical calculations reveal that the incorporation of HEACs lead to a rehybridization of the 3d orbital configuration of Fe‐N4, which helps to balance the adsorption/desorption energy of oxygenated intermediates. In situ spectroscopy further reveals that the rate‐limiting step of OH* desorption on HEAC/Fe─NC in oxygen reduction reaction (ORR) is more facile compared to atomic Fe─NC, implying a higher ORR activity. Moreover, the synergistic effect of diffusion activation barriers and configuration entropy contributes to the structural stability of HEAC/Fe─NC, resulting in remarkable durability. Consequently, this unique catalyst exhibits half‐wave potentials of 0.927 and 0.828 V in an aqueous solution of KOH (0.1 m) and HClO4 (0.1 m), respectively, along with excellent durability. The findings propose a novel strategy for modulating the electronic structure of metallic SAs catalysts and enhancing their stability through strong interactions between SAs and HEACs. [ABSTRACT FROM AUTHOR]

Current–voltage hysteresis of perovskite solar cells (PSCs) has raised the concern of accurate performance measurement in practice. Although various theories have been proposed to elucidate this phenomenon, the origin of hysteresis is still an open question. Herein, the use of guanidinium cation (Gu+)‐dopant is demonstrated to tailor the crystal structure of mixed‐cation formamidinium‐cesium lead triiodide (FA0.83Cs0.17PbI3) perovskite, resulting in an improved energy conversion efficiency and tunable current–voltage hysteresis characteristic in planar solar cells. Particularly, when the concentration of Gu‐dopant for the perovskite film increases, the normal hysteresis initially observed in the pristine PSC is first suppressed with 2%‐Gu‐dopant, then changed to inverted hysteresis with a higher Gu‐dopant. The hysteresis tunability behavior is attributed to the interplay of charge/ion accumulation and recombination at interfaces in the PSC. Furthermore, compared to the cell without Gu+‐dopant, the optimal content of 2% Gu+‐dopant also increases the device efficiency by 14%, reaching over 17% under one sun illumination. A new method to control current–voltage hysteresis of planar structured FA0.83Cs0.17PbI3 perovskite solar cells (PSCs) is presented while enhancing device efficiency through tailoring the crystal structure of the perovskite compound with a guanidinium cation (Gu+)‐dopant. New insights into the correlation of the dynamics of device hysteresis with the interfacial charge recombination and accumulation in the PSCs are revealed. [ABSTRACT FROM AUTHOR]