Search

High-entropy materials, for both complexity in structure and superiority in performance, have been widely confirmed to be one possible kind of advanced electrocatalyst. Significant efforts have been dedicated to modeling the atomic-level details of high-entropy catalysts to improve the viability for bottom-up design of advanced electrocatalysts. In this review, first, we survey developments in various modeling methods that are based on density functional theory. We review progress in density functional theory simulations for emulating different high-entropy electrocatalysts. Then, we review the advancements in simulations of high-entropy materials for electrocatalytic applications. Finally, we present prospects in this field. Abbreviations: HEMs: high-entropy materials; CCMs: compositionally complex materials; DFT: density functional theory; LDA: local density approximation; GGA: generalized gradient approximation; VASP: Vienna Ab initio simulation package; ECP: effective core potential; PAW: projector-augmented wave potential; VCA: virtual crystal approximation; CPA: coherent potential approximation; SQS: special quasi-random structures; SSOS: small set of ordered structures; SLAE: similar local atomic environment; HEAs: high-entropy alloys; FCC: face-centered cubic; BCC: body-centered cubic; HCP: hexagonal close-packed; ORR: oxygen reduction reaction; OER: oxide evolution reaction; HER: hydrogen evolution reaction; RDS: rate-limiting step; AEM: adsorbate evolution mechanism; LOM: lattice oxygen oxidation mechanism; HEOs: high-entropy oxides; OVs: oxygen vacancies; PDOS: projected densities of states; ADR: ammonia decomposition reaction; NRR: nitrogen reduction reaction; CO2RR: CO2 reduction reaction; TMDC: transition metal dichalcogenide; TM: transition metal; AOR: alcohol oxidation reaction; GOR: glycerol oxidation reaction; UOR: urea oxidation reaction; HEI: high-entropy intermetallic. This paper reviews recent developments in the field of atomistic simulations of high-entropy electrocatalysts, one of emerging state-of-the-art catalytic materials. [ABSTRACT FROM AUTHOR]

33928950 5 Wang K., He J., Zhang M., Wang H., Zhang G. Magnon-phonon interaction in antiferromagnetic two-dimensional MXenes. 26722716 3 Webster L., Liang L., Yan J.-A. Distinct spin-lattice and spin-phonon interactions in monolayer magnetic CrI3. In contrast to acoustic phonons, optical phonon modes can be used to evaluate interlayer coupling, spin-orbit coupling, magneto-optic coupling, and the number of atomic layers through Raman spectroscopy measurement. [Extracted from the article]

Graphical abstract Highlights • The most stable structures of the vertical heterostructures of MX 2 /BP (M =Mo, W; X =S, Se) are obtained. • Van der Waals interaction are found in these heterostructures. • Type-II band alignment are addressed in MoSe 2 /BP and WSe 2 /BP which can separate the photogenerated-charge. • All these heterostructures have excellent ability of optical absorption in the near-infrared and visible regions. Abstract Van der Waals (vdW) heterostructure can improve the performance of the 2D materials and provide more applications. Based on density functional theory (DFT) calculations, the properties of vertical heterostructures formed by transition metal dichalcogenides (TMDs) MX 2 (M = Mo, W; X = S, Se) and boron nitride (BP) were addressed. In particular, the vdW interaction exist in all these heterostructures instead of covalent bonding. The MoSe 2 /BP and WSe 2 /BP vdW heterostructures possess direct bandgap characterized by type-II band alignment and powerful built-in electric field across the interface, which can effectively separate the photogenerated-charge. Meanwhile, the MoS 2 /BP and WS 2 /BP vdW heterostructures also have the direct bandgap and intrinsic type-I band alignment. Furthermore, all heterostructures exhibit excellent optical absorption in the visible and near-infrared regions. Our investigation shows an effective method to design new vdW heterostructures based on TMDs and explores their applications for photocatalytic, photovoltaic, and optical devices. [ABSTRACT FROM AUTHOR]

Abstract Four vertical heterostructures based on two-dimensional transition-metal dichalcogenides (TMDs) – MoS 2 /GeC, MoSe 2 /GeC, WS 2 /GeC, and WSe 2 /GeC, were studied by density functional theory calculations to investigate their structure, electronic characteristics, principle of photogenerated electron–hole separation, and optical-absorption capability. The optimized heterostructures were formed by van der Waals (vdW) forces and without covalent bonding. Their most stable geometric configurations and band structures display type-II band alignment, which allows them to spontaneously separate photogenerated electrons and holes. The charge difference and built-in electric field across the interface of these vdW heterostructures also contribute to preventing the photogenerated electron–hole recombination. Finally, the high optical absorption of the four TMD-based vdW heterostructures in the visible and near-infrared regions indicates their suitability for photocatalytic, photovoltaic, and optical devices. Highlights • The most stable structures of the vertical heterostructures of TMDs/GeC are obtained. • Van der Waals interaction are found in these heterostructures. • Type-II band alignment are addressed in all the vdW heterostructures which can separate the photogenerated-charge. • All the structures are suitable for photocatalytic, photovoltaic, and optical devices. • All the structures show high optical absorption in the visible and NIR ranges. [ABSTRACT FROM AUTHOR]

The present study is focused on the nature of the structure-properties relationships of 2,5-diaryl fulleropyrrolidine derivatives. 2,5-diaryl fulleropyrrolidines modified by electron donor groups, and doped endohedrally with alkali metal ions (M@1-D , D = –CH 3 , –OCH 3 , –NH 2 ; M = Li+, Na+, K+) are designed and investigated. Surprisingly, the K@1-NH 2 shows remarkable NLO response. [Display omitted] • The 2,5-Diaryl fulleropyrrolidine derivatives are designed and investigated. • M@1-D shows remarkable NLO response compared to 1-D and M@1. • The K+@1-NH 2 possesses the largest β tot value of 4.58 × 103 a.u.. • Uv–vis absorption spectrum explains tendency of the β tot value. The present study is focused on the nature of the structure-properties relationships of the 2,5-diaryl fulleropyrrolidine (1) derivatives by the density functional theory (DFT). 1 derivatives are designed and investigated, which are modified by electron donor groups and doped with alkali metal ions (1-D , M@1 and M@1-D , D = –CH 3 , –OCH 3 , –NH 2 ; M = Li+, Na+, K+). Surprisingly, M@1-D compounds show a remarkable NLO response compared to 1-D and M@1. The K+@1-NH 2 possesses the largest β tot value of 4.58 × 103 a.u.. Furthermore, the Uv–vis absorption spectrum by the time-dependent (TD-DFT) method is carried out to study tendency of the NLO responses for 1-D , M@1 and M@1-D. Calculated maximum absorption wavelength of K+@1-NH 2 is significantly red-shifted compared to 1-NH 2 and K+@1. The current work presents that 2,5-diaryl fulleropyrrolidine modified by introducing electron donor groups and doping alkali metal ions is a good candidate for well-performance NLO nanomaterial. [ABSTRACT FROM AUTHOR]

Efficient electrocatalysts based on earth-abundant elements are urgently required for promoting the efficiency of electrochemical water splitting. In this work, heterostructures of CoNi 2 S 4 /Ni 3 S 2 on nickel foam (CoNi 2 S 4 /Ni 3 S 2 @NF) are synthesized by a facile one-step hydrothermal method as promising bifunctional electrocatalysts. To achieve an electrocatalytic current density of 10 mA cm−2 in 1 M KOH solution, the CoNi 2 S 4 /Ni 3 S 2 @NF electrode requires overpotential as low as 171 mV and 243 mV for HER and OER, respectively. Furthermore, the overall water splitting device with CoNi 2 S 4 /Ni 3 S 2 @NF electrode as both cathode and anode requires 1.65 V to offer current density of 10 mA cm−2. Density functional theory calculations reveal that the strong coupling interactions between CoNi 2 S 4 and Ni 3 S 2 synergistically optimized the electronic structure, thus enhancing the electrochemical water splitting performances. Surfaces oxidation of CoNi 2 S 4 /Ni 3 S 2 @NF electrode is considered to hinder the electrochemical activities for OER. The present work not only provides a promising bifunctional electrocatalyst for water splitting but also expands the applications of CoNi 2 S 4 based materials. • CoNi 2 S 4 /Ni 3 S 2 catalyst was prepared via a facile hydrothermal method. • Electrocatalytic performances of CoNi 2 S 4 /Ni 3 S 2 @NF toward water splitting were investigated for the first time. • DFT calculations revealed the coupling interactions between CoNi 2 S 4 and Ni 3 S 2 can optimize the electronic structure. [ABSTRACT FROM AUTHOR]

The magnetic and electronic behaviors of metal atoms adsorbed MoSi 2 N 4 monolayer have been systematically researched by density functional theory. The results reveal that the most stable sites of MoSi 2 N 4 monolayer adsorbed by various metal are diverse. The band structures of the Li–MoSi 2 N 4 system exhibit the nonmagnetic metal behavior, while the Pd–MoSi 2 N 4 , Pt–MoSi 2 N 4 , and Zn–MoSi 2 N 4 systems indicate nonmagnetic semiconductors. Meanwhile, K–MoSi 2 N 4 and Na–MoSi 2 N 4 systems emerge magnetic metal character, and the Ag–MoSi 2 N 4 , Au–MoSi 2 N 4 , Bi–MoSi 2 N 4 , Fe–MoSi 2 N 4 , Mn–MoSi 2 N 4 , Pb–MoSi 2 N 4 , and V–MoSi 2 N 4 systems appear magnetic semiconductor features, while the magnetic moments are 1.00 μ B , 1.00 μ B , 1.00 μ B , 3.00 μ B , 5.87 μ B , 4.26 μ B, 0.37 μ B , 0.52 μ B , 1.94 μ B , 2.86 μ B , 3.85 μ B , and 4.84 μ B , respectively. Furthermore, the charge transfer arises between the metal atoms and MoSi 2 N 4. Importantly, the work function of MoSi 2 N 4 system decreases greatly after metal adsorption, in particular, the work function of Li–MoSi 2 N 4 is lower 74.95% than that of pristine MoSi 2 N 4. Therefore, it indicates that metal atoms adsorbed MoSi 2 N 4 systems can be used to manufacture spintronic and vacuum electron emission nanodevices. [Display omitted] • The Pd–MoSi 2 N 4 , Pt–MoSi 2 N 4 , and Zn–MoSi 2 N 4 systems indicate nonmagnetic semiconductors. • The Ag–MoSi 2 N 4 , Au–MoSi 2 N 4 , Bi–MoSi 2 N 4 , Fe–MoSi 2 N 4 , Mn–MoSi 2 N 4 , Pb–MoSi 2 N 4 , and V–MoSi 2 N 4 systems appear magnetic semiconductor features. • The work function of MoSi 2 N 4 system decreases greatly after metal adsorption, in particular, the work function of Li–MoSi 2 N 4 is lower 74.95% than that of pristine MoSi 2 N 4. [ABSTRACT FROM AUTHOR]

• An innovative route was proposed to prepare cheap Cl-rich porous biochar for effective mercury capture. • The bio-chars possessed high chlorine-containing active sites on the surface of hierarchical pores. • The reaction mechanism was identified to follow a typical chemisorption process. Mercury emission from coal-fired flue gas has threatened the natural environment. It is an urgent demand for developing more effective and cheap sorbents to substitute the high-cost commercial activated carbon for removing elemental mercury. In this work, an innovative route is proposed to prepare hierarchical porous biochar via one-step co-pyrolysis of waste rice straw and polyvinyl chloride with CaCO 3 as a template. The optimum material (RPC-313) delivers over 90% capture performance for Hg0 at 120 °C under 225000 h−1 of GHSV. Characterization results show that the high efficiency of this sorbent is attributed to the synergistic effect of high chlorine-containing active sites (2.02%) and the developed hierarchically pores (large specific surface area of 554.9 m2/g and pore volume of 0.6397 m3/g). It also indicates that during the preparation process, the H–Cl generated from PVC react with C C groups on the surface of bio-chars to form the C–Cl groups. The employed CaCO 3 as a template creates a hierarchical structure for the sorbent. Moreover, the mercury reaction mechanism is identified as a chemisorption process which can be divided into two parts: adsorption and oxidation. An excellent mesoporous ratio (70%) accelerates mercury diffusion inside the CaCO 3 -activated adsorbent. And the C–Cl groups are directly beneficial for the adsorption of Hg0 according to DFT calculation. Furthermore, the C–Cl bonds and active oxygen species on the micropores surface of adsorbent act as reaction sites for oxidizing the adsorbed Hg0 into HgCl 2 and HgO, respectively. The HgCl is considered as an intermediate in the reaction pathway. [ABSTRACT FROM AUTHOR]