Electrochemical nitrogen reduction reaction (NRR) under ambient conditions provides an avenue to produce carbon‐free hydrogen carriers. However, the selectivity and activity of NRR are still hindered ...by the sluggish reaction kinetics. Nitrogen Vacancies on transition metal nitrides are considered as one of the most ideal active sites for NRR by virtue of their unique vacancy properties such as appropriate adsorption energy to dinitrogen molecule. However, their catalytic performance is usually limited by the unstable feature. Herein, a new 2D layered W2N3 nanosheet is prepared and the nitrogen vacancies are demonstrated to be active for electrochemical NRR with a steady ammonia production rate of 11.66 ± 0.98 µg h−1 mgcata−1 (3.80 ± 0.32 × 10−11 mol cm−2 s−1) and Faradaic efficiency of 11.67 ± 0.93% at −0.2 V versus reversible hydrogen electrode for 12 cycles (24 h). A series of ex situ synchrotron‐based characterizations prove that the nitrogen vacancies on 2D W2N3 are stable by virtue of the high valence state of tungsten atoms and 2D confinement effect. Density function theory calculations suggest that nitrogen vacancies on W2N3 can provide an electron‐deficient environment which not only facilitates nitrogen adsorption, but also lowers the thermodynamic limiting potential of NRR.
Nitrogen vacancies on 2D layered W2N3 reveal stable and efficient nitrogen reduction performance. The activity and selectivity of the unique active sites are confirmed by mutually corroborating electrochemical experiments and theoretical computation. The nitrogen vacancies on W2N3 have an electron deficient environment for the acceptance of the lone‐pair electrons of N2, which can facilitate dinitrogen molecule adsorption and activation.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Rechargeable aqueous zinc‐ion batteries (ZIBs) are promising energy‐storage devices owing to their low cost and high safety. However, their energy‐storage mechanisms are complex and not well ...established. Recent energy‐storage mechanisms of ZIBs usually depend on cationic redox processes. Anionic redox processes have not been observed owing to the limitations of cathodes and electrolytes. Herein, we describe highly reversible aqueous ZIBs based on layered VOPO4 cathodes and a water‐in‐salt electrolyte. Such batteries display reversible oxygen redox chemistry in a high‐voltage region. The oxygen redox process not only provides about 27 % additional capacity, but also increases the average operating voltage to around 1.56 V, thus increasing the energy density by approximately 36 %. Furthermore, the oxygen redox process promotes the reversible crystal‐structure evolution of VOPO4 during charge/discharge processes, thus resulting in enhanced rate capability and cycling performance.
Rezinking zinc batteries: Aqueous zinc‐ion batteries based on VOPO4 cathodes and a water‐in‐salt electrolyte displayed highly reversible oxygen redox chemistry at high voltages (see graph). The oxygen redox process not only led to increased capacity and a higher average operating voltage of the Zn/VOPO4 batteries, but also improved rate capability and cycling performance.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Single atoms catalysts’ (SACs) applications in the energy storage field are hindered by their insufficient stability and poor recyclability due to their oxidation and agglomeration. To address this ...challenge, herein, a Co‐CMS composite material is synthesized by confining Co SACs into the highly ordered pores of the carbon molecular sieve (CMS). Related theoretical and experimental methods prove that the microporous trapping and hydroxyl doping of CMS are favorable for synergistically stabilizing the precursor and contributing to the subsequent conversion of single atoms with strong interactions between Co, O, and N. The unique 3D spiral pore structure of CMS facilitates the mass transfer of reactants and the highly dispersed Co single atoms confined in CMS increase the active sites. These properties are ideal for oxygen reduction reaction catalysts. Benefiting from the above‐mentioned superiority, the Co‐CMS cathode exhibits superior performance in a rechargeable Zn–air battery with a lower charge–discharge voltage gap of 0.77 V and a power density of 219 mW cm−2. The applications of Co‐CMS catalysts are also extended to other metal–air batteries in this work, which further highlights the advantages of carbon molecular sieves in stabilizing SACs materials.
A new strategy for using the confinement effect of hierarchical carbon molecular sieves (CMS) to stabilize single atoms is deeply studied. This strategy enables the fabrication of a satisfactory oxygen reduction reaction catalyst. The synergistic effect of the micropore capture effect and the hydroxyl group of CMS produce excellent results. The Co‐CMS catalyst displays promising applications in the field of metal–air batteries.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Jasmonic acid (JA) is an endogenous growth-regulating substance, initially identified as a stress-related hormone in higher plants. Similarly, the exogenous application of JA also has a regulatory ...effect on plants. Abiotic stress often causes large-scale plant damage. In this review, we focus on the JA signaling pathways in response to abiotic stresses, including cold, drought, salinity, heavy metals, and light. On the other hand, JA does not play an independent regulatory role, but works in a complex signal network with other phytohormone signaling pathways. In this review, we will discuss transcription factors and genes involved in the regulation of the JA signaling pathway in response to abiotic stress. In this process, the JAZ-MYC module plays a central role in the JA signaling pathway through integration of regulatory transcription factors and related genes. Simultaneously, JA has synergistic and antagonistic effects with abscisic acid (ABA), ethylene (ET), salicylic acid (SA), and other plant hormones in the process of resisting environmental stress.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In this paper, a new ensemble forecasting model for short-term load forecasting (STLF) is proposed based on extreme learning machine (ELM). Four important improvements are used to support the ELM for ...increased forecasting performance. First, a novel wavelet-based ensemble scheme is carried out to generate the individual ELM-based forecasters. Second, a hybrid learning algorithm blending ELM and the Levenberg-Marquardt method is proposed to improve the learning accuracy of neural networks. Third, a feature selection method based on the conditional mutual information is developed to select a compact set of input variables for the forecasting model. Fourth, to realize an accurate ensemble forecast, partial least squares regression is utilized as a combining approach to aggregate the individual forecasts. Numerical testing shows that proposed method can obtain better forecasting results in comparison with other standard and state-of-the-art methods.
Visible‐light‐driven conversion of CO2 into chemical fuels is an intriguing approach to address the energy and environmental challenges. In principle, light harvesting and catalytic reactions can be ...both optimized by combining the merits of homogeneous and heterogeneous photocatalysts; however, the efficiency of charge transfer between light absorbers and catalytic sites is often too low to limit the overall photocatalytic performance. In this communication, it is reported that the single‐atom Co sites coordinated on the partially oxidized graphene nanosheets can serve as a highly active and durable heterogeneous catalyst for CO2 conversion, wherein the graphene bridges homogeneous light absorbers with single‐atom catalytic sites for the efficient transfer of photoexcited electrons. As a result, the turnover number for CO production reaches a high value of 678 with an unprecedented turnover frequency of 3.77 min−1, superior to those obtained with the state‐of‐the‐art heterogeneous photocatalysts. This work provides fresh insights into the design of catalytic sites toward photocatalytic CO2 conversion from the angle of single‐atom catalysis and highlights the role of charge kinetics in bridging the gap between heterogeneous and homogeneous photocatalysts.
Single‐atom Co sites coordinated on partially oxidized graphene nanosheets can serve as a highly active and durable heterogeneous catalyst for CO2 conversion, wherein the graphene bridges homogeneous light absorbers with single‐atom catalytic sites for the efficient transfer of photoexcited electrons. This design enables a turnover frequency of 3.77 min−1, superior to those obtained with conventional heterogeneous photocatalysts.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Abstract
The design of efficient and stable photocatalysts for robust CO
2
reduction without sacrifice reagent or extra photosensitizer is still challenging. Herein, a single-atom catalyst of ...isolated single atom cobalt incorporated into Bi
3
O
4
Br atomic layers is successfully prepared. The cobalt single atoms in the Bi
3
O
4
Br favors the charge transition, carrier separation, CO
2
adsorption and activation. It can lower the CO
2
activation energy barrier through stabilizing the COOH* intermediates and tune the rate-limiting step from the formation of adsorbed intermediate COOH* to be CO* desorption. Taking advantage of cobalt single atoms and two-dimensional ultrathin Bi
3
O
4
Br atomic layers, the optimized catalyst can perform light-driven CO
2
reduction with a selective CO formation rate of 107.1 µmol g
−1
h
−1
, roughly 4 and 32 times higher than that of atomic layer Bi
3
O
4
Br and bulk Bi
3
O
4
Br, respectively.
Great attention has been focused on the design of electrocatalysts to enable electrochemical water splitting-a technology that allows energy derived from renewable resources to be stored in readily ...accessible and non-polluting chemical fuels. Herein we report a bifunctional nanotube-array electrode for water splitting in alkaline electrolyte. The electrode requires the overpotentials of 58 mV and 184 mV for hydrogen and oxygen evolution reactions respectively, meanwhile maintaining remarkable long-term durability. The prominent performance is due to the systematic optimization of chemical composition and geometric structure principally-that is, abundant electrocatalytic active sites, excellent conductivity of metallic 1T' MoS
, synergistic effects among iron, cobalt, nickel ions, and the superaerophobicity of electrode surface for fast mass transfer. The electrode is also demonstrated to function as anode and cathode, simultaneously, delivering 10 mA cm
at a cell voltage of 1.429 V. Our results demonstrate substantial improvement in the design of high-efficiency electrodes for water electrolysis.
Lithium metal is considered a “Holy Grail” of anode materials for high‐energy‐density batteries. However, both dendritic lithium deposition and infinity dimension change during long‐term cycling have ...extremely restricted its practical applications for energy storage devices. Here, a thermal infusion strategy for prestoring lithium into a stable nickel foam host is demonstrated and a composite anode is achieved. In comparison with the bare lithium, the composite anode exhibits stable voltage profiles (200 mV at 5.0 mA cm−2) with a small hysteresis beyond 100 cycles in carbonate‐based electrolyte, as well as high rate capability, significantly reduced interfacial resistance, and small polarization in a full‐cell battery with Li4Ti5O12 or LiFePO4 as counter electrode. More importantly, in addition to the fact that lithium is successfully confined in the metallic nickel foam host, uniform lithium plating/stripping is achieved with a low dimension change (merely ≈3.1%) and effective inhibition of dendrite formation. The mechanism for uniform lithium stripping/plating behavior is explained based on a surface energy model.
A Li–Ni composite anode is achieved via a thermal infusion strategy. It exhibits stable voltage profiles (90 mV at 1.0 mA cm−2) with small hysteresis beyond 100 cycles, as well as low dimension change and effective dendrite inhibition after 100 cycles in a symmetric cell.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Single atoms immobilized on metal–organic frameworks (MOFs) with unique nanostructures have drawn tremendous attention in the application of catalysis but remain a great challenge. Various single ...noble‐metal atoms have now been successfully anchored on the well‐defined anchoring sites of the zirconium porphyrin MOF hollow nanotubes, which are probed by aberration‐corrected scanning transmission electron microscopy and synchrotron‐radiation‐based X‐ray absorption fine‐structure spectroscopy. Owing to the hollow structure and excellent photoelectrochemical performance, the HNTM‐Ir/Pt exhibits outstanding catalytic activity in the visible‐light photocatalytic H2 evolution via water splitting. The single atom immobilized on MOFs with hollow structures are expected to pave the way to expand the potential applications of MOFs.
Single noble metal atoms can be successfully immobilized on the well‐defined anchoring sites of zirconium–porphyrin MOF hollow nanotubes. Owing to the hollow structure and excellent photoelectrochemical performance, HNTM‐Ir/Pt exhibits outstanding catalytic activity in the visible‐light photocatalytic H2 evolution via water splitting.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
PDF
