The electrocatalytic reduction of naturally abundant N
2
to NH
3
is an attractive approach to replace the Haber-Bosch nitrogen-fixation process that causes enormous energy consumption and greenhouse ...gas emissions. However, designing high-performance catalysts toward the electrocatalytic N
2
reduction reaction (eNRR) remains one of the greatest challenges in this area. Herein, high-throughput screening of catalysts for the NRR among a series of transition metal atoms supported on a defective hexagonal boron nitride (h-BN) nanosheet is performed through spin-polarized density functional theory (DFT) computations. Strikingly, among the 18 candidates, the V/Tc atom anchored on a defective h-BN monolayer (V@BN and Tc@BN) showed good NRR activity with relatively low onset potentials. Particularly, V@BN was found to exhibit outstanding catalytic activity for the NRR
via
an enzymatic pathway with an extremely low overpotential of 0.25 V. The value is significantly lower than that on the Ru (0001) stepped surface that has the best NRR catalytic performance among bulk metal catalysts. The novel NRR activity of V@BN is attributed to the enhanced electrical conductivity due to V-doping, the "donation-backdonation" process for N
2
activation, and the highly centralized spin-polarization on the V atom. This work not only provides a quite promising catalyst for the NRR but also provides new insights for the rational design of single-atom NRR catalysts.
A single V atom anchored on h-BN exhibits outstanding catalytic activity for the NRR with a low onset potential of 0.25 V.
Growing demand for clean and renewable energy resources has sparked intensive research on the development of an effective strategy to prepare non-noble metal electrocatalysts for oxygen evolution ...reaction (OER). Herein, we report a new type of N-doped carbon coated CoP particle/carbon nanotube composite (CNT-NC-CoP) has been synthesized by in situ nucleation and growth of ZIF-67 nanoparticles onto carbon nanotubes, which subsequently is treated with carbonization and phosphorization. Unique hierarchical structure endows as-obtained CNT-NC-CoP with high specific surface area, abundant exposed active sites, quick ion diffusion path, and good electrical conductivity, thus exhibiting the highest electrocatalytic capability with the low overpotential of 251 mV at the current density of 10 mA cm−2 and remaining long-term durability (overlapping LSV curve after 10 h). Besides, density functional theory (DFT) calculations reveal that CoOOH/graphene charged surfaces are more effective for facilitating intermediates adsorption and improving the corresponding catalytic activity.
Schematic illustration of the synthesis of N-doped carbon coated CoP particle/carbon nanotube composite, which has been prepared by in situ growth of ZIF-67 nanoparticles onto PDA-coated carbon nanotubes, subsequently being treated with carbonization and phosphorization. Display omitted
The thermoelectric conversion efficiency of a material relies on a dimensionless parameter (ZT = S
σT/κ). It is a great challenge in enhancing the ZT value basically due to that the related transport ...factors of most of the bulk materials are inter-conditioned to each other, making it very difficult to simultaneously optimize these parameters. In this report, the negative correlation between power factor and thermal conductivity of nano-scaled SnS
multilayers is predicted by high-level first-principle computations combined with Boltzmann transport theory. By diminishing the thickness of SnS
nanosheet to about 3 L, the S and σ along a direction simultaneously increase whereas κ decreases, achieving a high ZT value of 1.87 at 800 K. The microscopic mechanisms for this unusual negative correlation in nano-scaled two dimensional (2D) material are elucidated and attributed to the quantum confinement effect. The results may open a way to explore the high ZT thermoelectric nano-devices for the practical thermoelectric applications.
Nonlinear optical (NLO) materials have received unprecedented attention owing to their capability of frequency conversion in the photoelectric fields. Yet, how to acquire a crystal with a ...noncentrosymmetric (NCS) structure is still a grand challenge for the NLO material. Herein, a new quaternary NCS oxychalcogenide, SrGeOSe2, was successfully designed and synthesized using the known centrosymmetric SrGeO3 as a maternal structure through a generic partial isovalent anion substitution (PIAS) strategy. SrGeOSe2 belongs to the NCS space group P212121 (no.19) and features a one-dimensional (1D) chain made by heteroligand GeO2Se2 asymmetric building units. Such a new compound exhibits desirable comprehensive performance, which suggests a promising IR-NLO material: type-I phase-matching feature, strong powder second-harmonic generation intensity (d ij = 1.3 × commercial AgGaS2), and giant powder laser-induced damage threshold (36 × commercial AgGaS2). Furthermore, the systematic theoretical investigations have been performed for the deep understanding of the correlation between the NCS structure and the NLO property. More importantly, this work pioneers a new molecular engineering strategy for NCS compounds that could be extended to other NLO materials.
Thermoelectrics interconvert heat to electricity and are of great interest in waste heat recovery, solid-state cooling and so on. Here we assessed the potential of SnS2 and SnSe2 as thermoelectric ...materials at the temperature gradient from 300 to 800 K. Reflecting the crystal structure, the transport coefficients are highly anisotropic between a and c directions, in particular for the electrical conductivity. The preferred direction for both materials is the a direction in TE application. Most strikingly, when 800 K is reached, SnS2 can show a peak power factor (PF) of 15.50 μW cm(-1) K(-2) along the a direction, while a relatively low value (11.72 μW cm(-1) K(-2)) is obtained in the same direction of SnSe2. These values are comparable to those observed in thermoelectrics such as SnSe and SnS. At 300 K, the minimum lattice thermal conductivity (κmin) along the a direction is estimated to be about 0.67 and 0.55 W m(-1) K(-1) for SnS2 and SnSe2, respectively, even lower than the measured lattice thermal conductivity of Bi2Te3 (1.28 W m(-1) K(-1) at 300 K). The reasonable PF and κmin suggest that both SnS2 and SnSe2 are potential thermoelectric materials. Indeed, the estimated peak ZT can approach 0.88 for SnSe2 and a higher value of 0.96 for SnS2 along the a direction at a carrier concentration of 1.94 × 10(19) (SnSe2) vs. 2.87 × 10(19) cm(-3) (SnS2). The best ZT values in SnX2 (X = S, Se) are comparable to that in Bi2Te3 (0.8), a typical thermoelectric material. We hope that this theoretical investigation will provide useful information for further experimental and theoretical studies on optimizing the thermoelectric properties of SnX2 materials.
By varying the stoichiometric ratio of Eu super(3+), Tb super(3+) and Gd super(3+) ions in a lanthanide metal-organic framework, a mixed-Ln MOF, Eu sub(0.0040)Tb sub(0.0460)Gd sub(0.9500)(BTB)(DMSO) ...sub(2).H sub(2)O, has been designed to display white-light emission. In addition, the switch between blue, white, and yellow for this material has been achieved by controlling the energy transfer process.
Inspired by the recent practical application of two-dimensional (2D) nanomaterials as gas sensors, catalysts, and materials for waste gas disposal, herein, the adsorption behaviors of environmental ...gas molecules, including NO, CO, O2, CO2, NO2, H2O, H2S, and NH3, on the 2D pristine and defective MoSi2N4 (MSN) monolayers were systematically investigated using spin-polarized density functional theory (DFT) calculations. Our results reveal that all the gas molecules are physically adsorbed on the MSN surface with small charge transfer, but the electronic structures of NO, NO2, and O2 are obviously modified due to the in-gap states. The introduction of N vacancy on the MSN surface enhances the interaction between gas molecules and the substrate, especially for NO2 and O2. Interestingly, the adsorption type of NO and CO evolves from physisorption to chemisorption, which may be utilized in NO and CO catalytic reaction. Furthermore, the moderate adsorption strength and obvious changes in electronic properties of H2O and H2S on the defective MSN make them have promising prospects in highly sensitive and reusable gas sensors. This work offers several promising gas sensors based on the MSN monolayer and also provides a theoretical reference of other related 2D materials in the field of gas sensors, catalysts, and toxic gas disposal.
Carbonaceous materials are promising anode candidates for potassium‐ion batteries (PIBs) given its high conductivity, stable property, and abundant resource, while its practical implementation is ...still hampered by its limited capacity and inferior rate behavior. Herein, we report a superior carbonaceous anode through a combined strategy of carbon hybridization and heteroatom doping. In this composite, hollow carbon spindles (HCS) were anchored on the surface of graphene (G) followed with sulfur doping treatment, aiming to integrate the high conductivity of graphene, the good structure stability of HCS, and the S doping‐induced ample active sites. As a PIB anode, the S‐G@HCS composite can display high capacity (301 mA h g−1 at 0.1 A g−1 after 500 cycles) and long‐term cyclability up to 1800 cycles at 2 A g−1. Impressively, it can deliver an outstanding rate capacity of 215 mA h g−1 at 10 A g−1, which is superior to most carbon anodes as‐reported so far for PIBs. Experimental and theoretical analysis manifests that the construction of graphene/amorphous carbon interface as well as S doping enables the regulation of electronic structure and ion adsorption/transportation properties of carbonaceous material, thus accounting for the high capacity and superior rate capability of S‐G@HCS composite.
A combined carbon hybridization and sulfur doping strategy is developed for boosting the performance of carbonaceous materials. Benefiting from the synergistic effect of graphene/amorphous carbon heterointerface and S doping on the enhancement of electrical conductivity and ion transport/adsorption ability, as‐prepared S‐G@HCS exhibits high capacity and excellent rate performance (215 mA h g−1 at 10 A g−1), outperforming most reported carbon anodes.
The enhancements in thermoelectric (TE) performances of p-type skutterudites are usually limited due to the relatively low Seebeck coefficients owing to the higher carrier concentration and more ...impurity phases induced by inherent structural instability of a Fe-based skutterudite. As shown in this study, alloying engineering of Ni doping at Fe sites in a p-type CeFe3.8Co0.2Sb12 skutterudite can not only reduce the impurity phases with high thermal conductivity but also regulate the carrier concentration, and thus significantly increase the Seebeck coefficient. The thermal conductivity was largely suppressed due to the enhanced point defect phonon scattering and decreased hole concentration. As a result, a TE figure of merit ZT of the CeFe3.5Ni0.3Co0.2Sb12 sample reached 0.8, which is approximately 50% higher than that of a Ni-free sample. Appropriate Ni doping can maintain a high ZT at a high temperature by controlling the reduction in a band gap. Therefore, a high average ZT close to 0.8 at 650–800 K for CeFe3.5Ni0.3Co0.2Sb12 was obtained, which was comparable to or even higher than those of the reported Ce-filled Fe-based skutterudites due to the synergistic optimization of electrical and thermal performances. This study provides a strategy to synergistically optimize electrical–thermal performances of the p-type skutterudites by alloying engineering.
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