Interplay of spin-orbit coupling (SOC) and electron correlation generates a bunch of emergent quantum phases and transitions, especially topological insulators and topological transitions. We find ...that electron correlation will induce extra large SOC in multi-orbital systems under atomic SOC and change ground state topological properties. Using the Hartree–Fock mean field theory, phase diagrams of
p
x
/
p
y
orbital ionic Hubbard model on honeycomb lattice are well studied. In general, correction of strength of SOC
δ λ
∝ (
U
ʹ–
J
). Due to breaking down of rotation symmetry, form of SOC on multi-orbital materials is also changed under correlation. If a non-interacting system is close to fermionic instability, spontaneous generalized SOC can also be found. Using renormalization group, SOC is leading instability close to quadratic band-crossing point. Mean fields at quadratic band-crossing point are also studied.
Electrochemical reduction of carbon dioxide (CO2) to fuels and chemicals provides a promising solution for renewable energy storage and utilization. Among the many possible reaction pathways, CO2 ...conversion to carbon monoxide (CO) is the first step in the synthesis of more complex carbon‐based fuels and feedstocks, and holds great significance for the chemical industry. Herein, recent advances in heterogeneous catalysts for selective CO evolution from electrochemical reduction of CO2 are described. With Au catalysts as a paradigm, principles for catalyst design including size, morphology, and grain boundary densities tuning, surface modifications, as well as metal‐support interaction are comprehensively summarized, which shed light on the development of other transition metal catalysts targeting efficient CO2‐to‐CO conversion. In addition, recently emerged novel materials including transition metal single‐atom catalysts, which present significantly different catalytic behaviors compared to their bulk counterparts and thus open up many unexpected opportunities, are summarized. Furthermore, the technical aspects with respect to large‐scale production of CO are presented, focusing on the full‐cell design and implementation. Finally, short comments related to the future direction of real‐word CO2 electrolysis for CO supply are provided in terms of catalyst optimization and technical breakthrough.
Electrocatalytic CO2 reduction, powered by renewable energy sources, has provided a promising route for delocalized energy storage, chemical production applications, and more importantly, closing the carbon loop. The progress of CO2 electroreduction to CO is reviewed by introducing the recent advances in heterogeneous catalysts and the technical breakthroughs in large‐scale production of CO.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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We argue that the topological charge density wave phase in the quasi-2D Kagome superconductor AV3Sb5 is a chiral flux phase. Considering the symmetry of the Kagome lattice, we show ...that the chiral flux phase has the lowest energy among those states which exhibit 2×2 charge orders observed experimentally. This state breaks the time-reversal symmetry and displays anomalous Hall effect. The explicit pattern of the density of state in real space is calculated. These results are supported by recent experiments and suggest that these materials are new platforms to investigate the interplay between topology, superconductivity and electron–electron correlations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Precise electrochemical synthesis under ambient conditions has provided emerging opportunities for renewable energy utilization. Among many promising systems, the production of hydrogen peroxide ...(H2O2) from the cathodic oxygen reduction reaction (ORR) has attracted considerable interest in past decades due to the increasing market demands and the vital role of ORR in the electrocatalysis field. This work describes recent advances in cathodic materials for H2O2 synthesis from 2e- ORR. By using Pt as a stereotype, the tuning knobs are overviewed, including the intrinsic binding strength of oxygenated species, the intermediate diffusion path and the isolation of Pt–Pt ensembles that enable 2e- ORR pathway from 4e- total reduction. This knowledge is successfully applied to other transition metal systems and leads to the discovery of more efficient alloy catalysts with balanced improvement on both activity and selectivity. In addition, mesostructure engineering and heteroatoms doping strategies on carbon‐based materials, which significantly boost the H2O2 production efficiency as compared to intact carbon sites, are also reviewed. Finally, future directions and challenges of transferring developed catalysts from lab scale tests to pilot plant operations are briefly outlooked.
Electrocatalytic oxygen reduction into hydrogen peroxide, powered by renewable energy sources with green inputs of air and water, is a promising route for decentralized H2O2 generation and its onsite application. A focus review of designing principles and recent progress on cathodic materials for enhanced O2 reduction to H2O2 is provided.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The oxygen-evolution reaction (OER) is a key process in water-splitting systems, fuel cells, and metal–air batteries, but the development of highly active and robust OER catalyst by simple methods is ...a great challenge. Here, we report an in situ dynamic surface self-reconstruction that can dramatically improve the catalytic activity of electrocatalysts. A fluoride (F–)-incorporating NiFe hydroxide (NiFe-OH-F) nanosheet array was initially grown on Ni foam by a one-step hydrothermal method, which requires a 243 mV over-potential (η) to achieve a 10 mA cm–2 current density with a Tafel slope of 42.9 mV dec–1 in alkaline media. After the surface self-reconstruction induced by fluoride leaching under OER conditions, the surface of NiFe-OH-F was converted into highly mesoporous and amorphous NiFe oxide hierarchical structure, and the OER activity at η = 220 mV increases over 58-fold. The corresponding η at 10 mA cm–2 decreases to 176 mV with an extreme low Tafel slope of 22.6 mV dec–1; this performance is superior to that of the state-of-the-art OER electrocatalysts.
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The development of advanced catalysts for efficient electrochemical energy conversion technologies to alleviate the reliance on fossil fuels has attracted considerable interest in the last decades. ...Insight into the roles of reactive sites in nanomaterials is significant for understanding and implementing the design principles of nanocatalysts. Recently, the essential role of defects, including vacancies, reconstructed defects, and doped non-metal (or metal)-defect-based motifs, have been widely demonstrated to promote the diverse electrochemical processes (e.g., O2 or CO2 reduction reactions and H2 or O2 evolution reactions). Nevertheless, the in-depth exploration of the underlying defect electrocatalytic mechanism is still in its infancy. This review summarizes the state-of-the-art defect engineering strategies for designing highly efficient electrochemical nanocatalysts with special emphasis on the correlation between defect structures and electrocatalytic properties. Finally, some perspectives on the challenges and future research directions in this promising area are presented.
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Electrocatalytic energy conversion technologies have been widely considered a clean and sustainable way to alleviate the reliance on fossil fuels. The development of efficient and affordable electrocatalysts plays a key aspect in energy conversion processes by lowering the reaction kinetic barriers and thus boosting the efficiency and selectivity of diverse electrochemical reactions (e.g., oxygen and hydrogen evolution reactions and oxygen and carbon dioxide reduction reactions). Recently, defect engineering has emerged as a new strategy for tailoring the electronic structures and interface coordination; however, the role of “defect”-related sites in as-designed electrocatalysts has not yet been fully understood. In this review, we will shed light on the recent advances in tailoring nanomaterials from the aspects of constructing defect-based motifs as active sites for versatile electrochemical energy conversions as well as their underlying mechanism on structure-property correlations.
Recently, the essential role of defects, including vacancies, reconstructed defects, and doped non-metal/metal-defect-based motifs, has been widely demonstrated to promote the diverse electrochemical processes (e.g., O2/CO2 reduction reactions and H2/O2 evolution reactions). This review summarizes the state-of-the-art defect engineering strategies for designing highly efficient electrochemical nanocatalysts with special emphasis on the correlation between defect structures and electrocatalytic properties. Finally, some perspectives on the challenges and future research directions in this promising area are presented.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Fluorine, as the most electronegative element, can replace the oxygen ligands of functional groups under given conditions. These fluoride groups are more or less different from the pure oxide groups ...in composition, symmetry, polarizability, transmittancy,
etc.
The rational use of these differences is expected to improve the probability of noncentrosymmetric structures and the comprehensive performance of second-harmonic-generation (SHG) materials. In this feature article, we introduce the recent developments in fluoride selenite and tellurite SHG materials together with highlighting our contributions, including Se(
iv
) and Te(
iv
) compounds with (i) d
0
transition metal oxyfluoride octahedron, (ii) IIIA metal oxyfluoride octahedron, (iii) fluoride lone pair cation polyhedron, and (iv) other fluoride polyhedron. The future perspectives of fluoride selenite and tellurite SHG materials are also discussed.
Inclusion of the most electronegative fluorine can regulate the distortion direction and magnitude of the structure, bandgap, and second-harmonic-generation (SHG) efficiency of materials effectively.
Motivated by the recently observed insulating states in twisted bilayer graphene, we study the nature of the correlated insulating phases of the twisted bilayer graphene at commensurate filling ...fractions. We use the continuum model and project the Coulomb interaction onto the flat bands to study the ground states by using a Hartree-Fock approximation. In the absence of the hexagonal boron nitride substrate, the ground states are the intervalley coherence states at charge neutrality (filling ν = 0 , or four electrons per moiré cell) and at ν = − 1 / 4 and − 1 / 2 (three and two electrons per cell, respectively) and the C2T symmetry-broken state at ν = − 3 / 4 (one electron per cell). The hexagonal boron nitride substrate drives the ground states at all ν into C2T symmetry broken-states. Our results provide good reference points for further study of the rich correlated physics in the twisted bilayer graphene.
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Facile interconversion between CO2 and formate/formic acid (FA) is of broad interest in energy storage and conversion and neutral carbon emission. Historically, electrochemical CO2 reduction reaction ...to formate on Pd surfaces was limited to a narrow potential range positive of −0.25 V (vs RHE). Herein, a boron-doped Pd catalyst (Pd–B/C), with a high CO tolerance to facilitate dehydrogenation of FA/formate to CO2, is initially explored for electrochemical CO2 reduction over the potential range of −0.2 V to −1.0 V (vs RHE), with reference to Pd/C. The experimental results demonstrate that the faradaic efficiency for formate (ηHCOO– ) reaches ca. 70% over 2 h of electrolysis in CO2-saturated 0.1 M KHCO3 at −0.5 V (vs RHE) on Pd–B/C, that is ca. 12 times as high as that on homemade or commercial Pd/C, leading to a formate concentration of ca. 234 mM mg–1 Pd, or ca. 18 times as high as that on Pd/C, without optimization of the catalyst layer and the electrolyte. Furthermore, the competitive selectivity ηHCOO–/ηCO on Pd–B/C is always significantly higher than that on Pd/C despite a decreases of ηHCOO– and an increases of the CO faradaic efficiency (ηCO) at potentials negative of −0.5 V. The density functional theory (DFT) calculations on energetic aspects of CO2 reduction reaction on modeled Pd(111) surfaces with and without H-adsorbate reveal that the B-doping in the Pd subsurface favors the formation of the adsorbed HCOO*, an intermediate for the FA pathway, more than that of *COOH, an intermediate for the CO pathway. The present study confers Pd–B/C a unique dual functional catalyst for the HCOOH ↔ CO2 interconversion.
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10.
General Theory of Josephson Diodes Zhang, Yi; Gu, Yuhao; Li, Pengfei ...
Physical review. X,
11/2022, Volume:
12, Issue:
4
Journal Article
Peer reviewed
Open access
Motivated by recent progress in the superconductivity nonreciprocal phenomena, we study the general theory of Josephson diodes. The central ingredient for Josephson diodes is the asymmetric proximity ...process inside the tunneling barrier. From the symmetry breaking point of view, there are two types of Josephson diodes: inversion breaking and time-reversal breaking. For the inversion breaking case, applying voltage bias could effectively tune the proximity process like the voltage-dependent Rashba coupling or electric polarization giving rise to I_{c}(V)≠I_{c}(-V) and I_{r+}≠I_{r-}. For the time-reversal breaking case, the current flow could adjust the internal time-reversal breaking field like magnetism or time-reversal breaking electron-electron pairing, which leads to I_{c+}≠I_{c-}. All these results provide a complete understanding and the general principles of realizing Josephson diodes, especially the recently found NbSe_{2}/Nb_{3}Br_{8}/NbSe_{2} Josephson diodes.
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