Water splitting involves a hydrogen evolution reaction (HER) at the cathode and an oxygen evolution reaction (OER) at the anode, and OER has been considered as the major bottleneck for water splitting due to the sluggish reaction kinetics and high OO bond formation energy barrier caused by its four-electron coupling process. [2][3][4][5] Designing the external-and internal structure of electrocatalysts is fundamental to achieve high catalytic activities at low overpotential and equally important to the electrocatalysts themselves, the reaction efficiency also strongly depends on the mass transfer outside the electrode surface and electron transfer inside the electrode structure. [4][5][6] The mass transfer at the interfaces between the catalyst and electrolyte is responsible for the immediate supplying of electrolytes (and reactants) and associated with rapid release of bubbles generated by the reactions (O 2 gas, for the case of OER). [7] The kinetics of mass transfer as the rate-controlling step, therefore, govern the efficiency of the electrochemical reaction, by taking much larger time constant compared with that of the electron transfer. [8,9] For gas-evolving electrochemical system, bubbles may adhere to the catalyst's surface and block the active sites by forming bubble froth layers. This process
The promotion of magnetic field on catalytic performance has attracted extensive attention. However, little research has been reported on the performance of the oxygen evolution reaction (OER) for the modulating intrinsic magnetism of the catalyst under a magnetic field. Herein, we adjusted the intrinsic magnetism of the Co x Ni1–x Fe2O4-nanosheet by adjusting the ratio of Co and Ni, and researched the relationship between the OER activity and the intrinsic magnetism. The results indicate that the CoFe2O4-nanosheet has the most OER activity increases in the magnetic field due to the optimal intrinsic magnetism. The required overpotential of CoFe2O4-nanosheet@NF to reach a current density of 10 mA cm–2 was reduced by 21 mV under about 100 mT magnetic field compared with no magnetic field, and the degree of improvement of OER activity of different magnetic catalysts in the same magnetic field is positively correlated with the intrinsic magnetism of the catalyst. Therefore, magnetic field assistance provides a new, effective, and general strategy to improve the activity of electrodes for water splitting.
The slow oxygen evolution reaction (OER) limits water splitting, and external fields can help improve it. However, the effect of a single external field on OER is limited and unsatisfactory. Furthermore, the mechanism by which external fields improve OER is unclear, particularly in the presence of multiple fields. Herein, we propose a strategy for enhancing the OER activity of a catalyst using the combined effect of an optical‐magnetic field and study the mechanism of catalytic activity enhancement. Under the optical‐magnetic field, Co3O4 reduces the resistance by increasing the catalyst temperature. Meanwhile, CoFe2O4 further reduces the resistance via the negative magnetoresistance effect, thus decreasing the resistance from 16 Ω to 7.0 Ω. Additionally, CoFe2O4 acts as a spin polarizer, and electron polarization results in a parallel arrangement of oxygen atoms, which increases the kinetics of the OER under the magnetic field. Benefiting from the optical and magnetic response design, Co3O4/CoFe2O4@Ni foam requires an overpotential of 172.4 mV to reach a current density of 10 mA·cm−2 under an optical‐magnetic field, which is significantly higher than those of recently reported state‐of‐the‐art transition‐metal‐based catalysts.This article is protected by copyright. All rights reserved
The sluggish kinetics of oxygen evolution reaction (OER) remains a bottleneck for the electrocatalytic water splitting. In addition to improving the intrinsic activity of electrocatalysts, the electrode structure and external environment also have a significant influence on catalytic performance. Inspired by photosynthesis in plant leaves, a photothermal conversion strategy is proposed via the decoration of photothermal responsive MoS2/FeCoNiS‐nanotube (MoS2/FeCoNiS‐NT) on designed through‐hole porous nickel foam (PNF), defined as MoS2/FeCoNiS‐NT@PNF, to boost OER performance. The PNF facilitated bubble transport in OER by mimicking stomata structure of the leaf, and simultaneously, the MoS2/FeCoNiS‐NT increases light absorption and photothermal conversion by simulating the leaf epidermis. Benefiting from bionic structure and functional design, the MoS2/FeCoNiS‐NT@PNF electrode exhibits highly effective oxygen‐evolving ability and excellent photothermal conversion capacity (surface temperature: 25 °C → 52.3 °C, AM1.5G), which increases the intrinsic activity of electrocatalysts. With the assistance of optimized electrode structure and the photothermal effect, the MoS2/FeCoNiS‐NT@PNF electrode exhibits a low overpotential of 214 mV to achieve 50 mA cm−2. This research reveals that tuning the electrode structure can promote light absorption in the electrolyte in favor of OER performance, which can serve as an inspiration for the development of high‐performance catalytic electrodes.
.Nonlinear photonic crystals can be employed to generate holographic images in nonlinear optical processes. However, due to the limit of binary structure, the process of holographic imaging will lose part of the amplitude information and cause image hollowing, thus the imaging quality is reduced. Generative adversarial network, a deep learning network based on game theory, is used to restore images. The results of restoration show high similarity to the original images, effectively weakening the effect of image hollowing, suppressing the diffraction effect, and restoring grayscale values. This image post-processing approach completes the field of application of nonlinear holographic imaging, which is useful for non-visible source imaging, crosstalk avoidance, optical encryption, and so on.
We propose and investigate a class of aperiodic grating structure which can achieve perfect Talbot effect under certain conditions. The aperiodic grating structure is obtained by the superposition of two or more sine terms. In the case of two sine terms, the Talbot effect can be realized when the period ratio of two terms is arbitrary. While in the case of more than two sine terms, the period ratios of each term must meet certain extra conditions. The theory has been further verified by numerical simulations. It expands the field of Talbot effect and is of potential significance for subsequent research applications such as optical imaging and measurement.
In the second-harmonic generation processes involving Laguerre-Gaussian (LG) beams, the generated second-harmonic wave is generally composed of multiple modes with different radial quantum numbers. To generate single-mode second-harmonic LG beams, a type of improved quasi-phase-matching method is proposed. The Gouy phase shift has been considered in the optical superlattice designing and an adjustment phase item is introduced. By changing the structure parameters, each target mode can be phase-matched selectively, whose purity can reach up to 95%. The single LG mode generated from the optical superlattice can be modulated separately and used as the input signals in the mode division multiplexing system.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.