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.
Display omitted
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.
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.
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.
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.
Display omitted
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.
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.
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.
General Theory of Josephson Diodes Zhang, Yi; Gu, Yuhao; Li, Pengfei ...
Physical review. X,
11/2022, Letnik:
12, Številka:
4
Journal Article
Recenzirano
Odprti dostop
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.
In topological insulators doped with magnetic ions, spin-orbit coupling and ferromagnetism give rise to the quantum anomalous Hall effect. Here, we show that ins-wave superconductors with strong ...spin-orbit coupling, magnetic impurity ions can generate topological vortices in the absence of external magnetic fields. Such vortices, dubbed quantum anomalous vortices, support robust Majorana zero-energy modes when superconductivity is induced in the topological surface states. We demonstrate that the zero-energy bound states observed in Fe(Te,Se) superconductors are possible realizations of the Majorana zero modes in quantum anomalous vortices produced by the interstitial magnetic Fe. The quantum anomalous vortex matter not only advances fundamental understandings of topological defect excitations of Cooper pairing but also provides new and advantageous platforms for manipulating Majorana zero modes in quantum computing.
The scaling up of electrocatalytic CO2 reduction for practical applications is still hindered by a few challenges: low selectivity, small current density to maintain a reasonable selectivity, and the ...cost of the catalytic materials. Here we report a facile synthesis of earth-abundant Ni single-atom catalysts on commercial carbon black, which were further employed in a gas-phase electrocatalytic reactor under ambient conditions. As a result, those single-atomic sites exhibit an extraordinary performance in reducing CO2 to CO, yielding a current density above 100 mA cm−2, with nearly 100% selectivity for CO and around 1% toward the hydrogen evolution side reaction. By further scaling up the electrode into a 10 × 10-cm2 modular cell, the overall current in one unit cell can easily ramp up to more than 8 A while maintaining an exclusive CO evolution with a generation rate of 3.34 L hr−1 per unit cell.
Display omitted
•A facile and scalable synthesis of Ni single-atom catalysts on low-cost carbon blacks•Current densities over 100 mA cm−2 with nearly 100% selectivity for CO2-to-CO conversion•A practical CO generation rate of 3.34 L hr−1 was achieved in a 10 × 10-cm2 unit cell
Electrochemical reduction of CO2 to fuels and chemicals carries extraordinary significance for industry and is highly competitive with water electrolysis and downstream gas-phase CO2 reduction for addressing energy problems. Single-atom materials endowed with maximum atom efficiency, tunable coordination environments, and electronic structures have emerged as highly active catalysts for converting CO2 to CO. However, practical application of single-atom catalysts still seems to be too far away due to their complicated and high-cost materials synthesis, as well as low performance metrics. In this work, Ni single atoms on a low-cost carbon nanoparticle support are developed via a simple and scalable method, with record-high selectivity and activity toward CO production. Moreover, scaling up the electrodes into a modular cell achieves a high overall current while maintaining an exclusive CO evolution.
Earth-abundant Ni single atoms on commercial carbon black were synthesized in large quantities via an economic and scalable protocol, with record-high selectivity and activity toward CO production. Scaling up the electrodes into a 10 × 10-cm2 modular cell achieves a high overall current over 8 A while maintaining a nearly exclusive CO evolution.
PDF
