Latest ArticlesEfficient and stable electrocatalyst for oxygen evolution reaction (OER) in acidic environment is vital for polymer electrolyte membrane water electrolysis (PEMWE). In this work, we have devised the formation of heterostructured RuO2/MnO2 with nanoflower structure for acidic OER catalysis. Compared to commercial RuO2, the overpotential at 50 mA/cm2 is decreased by 36 mV, corresponding to a 3.7-fold better mass activity. The boosted acidic OER performance is attributed to the heterostructure inducing more electrons are filled in eg orbital of Ru atom triggering a better deprotonation of bridge oxygen atom in Ru-Obri-Mn structure evidenced by pH-independent cyclic voltammetry test. Moreover, RuO2/MnO2 sustains its acidic OER activity within 20 h, longer than commercial RuO2. The membrane electrode assembly (MEA) test suggests than only 2.18 V is required to achieve a current density of 5 A/cm2. The theoretical calculation reveals that the eg filling of Ru atom is increased from 2.18 to 2.39 after MnO2 incorporation, reducing the energy for the formation of *OOH moiety.
Charge-neutral method (CNM) is extensively used in investigating the performance of catalysts and the mechanism of N2 electrochemical reduction (NRR). However, disparities remain between the predicted potentials required for NRR by the CNM methods and those observed experimentally, as the CNM method neglects the charge effect from the electrode potential. To address this issue, we employed the constant electrode potential (CEP) method to screen atomic transition metal-N-graphene (M1/N-graphene) as NRR electrocatalysts and systematically investigated the underlying catalytic mechanism. Among eight types of M1/N-graphene (M1 = Mo, W, Fe, Re, Ni, Co, V, Cr), W1/N-graphene emerges as the most promising NRR electrocatalyst with a limiting potential as low as −0.13 V. Additionally, the W1/N-graphene system consistently maintains a positive charge during the reaction due to its Fermi level being higher than that of the electrode. These results better match with the actual circumstances compared to those calculated by conventional CNM method. Thus, our work not only develops a promising electrocatalyst for NRR but also deepens the understanding of the intrinsic electrocatalytic mechanism.
Surface-confined metal-organic frameworks have emerged as versatile structures with a broad spectrum of applications such as nanoelectronics, catalysis, sensing, and molecular storage, owing to their unique structural and electronic properties. However, the exploration and optimization of molecular networks typically involve resource-intensive trial-and-error experiments. The complexity comes from factors like metal nodes, organic ligands, substrates, and the preparation conditions. To address this challenge, high-throughput methodologies have been used in materials exploration. In this work, we explored a high-throughput method for preparing sub-monolayer metals with continuous coverage spread on metal surfaces. By employing a physical mask during metal deposition under ultra-high vacuum conditions, we achieved sample libraries with copper (Cu) and silver (Ag) adatoms on the metal substrates, and constructed surface-supported metal-organic frameworks with varying metal-to-molecule stoichiometric ratios. This approach facilitates the exploration of surface-confined metal-organic frameworks, particularly in terms of varying metal-to-ligand stoichiometric ratios, offering an efficient pathway to unlock the potential of these intricate two-dimensional networks.
CO2 electrolysis into formate is a promising technology with the potential to simultaneously alleviate energy shortages and global warming. However, the limited stability of the catalysts during long-term electrolysis hinders their widespread implementation. Herein, we show that a core-shell bimetallic BiAg catalyst with a multifaceted Janus structure at its core can achieve a stability of up to 300 h with a formate faradaic efficiency (FEformate) over 90% at −0.75 V vs. RHE (reversible hydrogen electrode) in an H-type cell. Our investigations reveal the important role of the Janus structure on the transfer of electrons, favoring their delocalization across the catalyst and enhancing their mobility. We propose that the compressive strain inclined to grain boundaries within this structure would lower the energy barrier for electrons transfer and promotes the cooperation between Ag and Bi. Indeed, Ag initiates the activation of CO2 through a series of cascade reactions and is subsequently hydrogenated on Bi. Additionally, our study suggests that Ag plays a crucial role in stabilizing the catalyst structure after long-term electrolysis. This work highlights a new strategy for tandem CO2 electrolysis, providing novel insights for the design of formate formation catalysts.
In order to protect the environment and economize energy, a nitrogen-fixing photocatalyst, VMCeact, is investigated in this work. This catalyst is prepared from a natural mineral, vermiculite, and modified by Ce-based metal-organic framework, Ce-UiO-66. Vermiculite was treated with formic acid; thus, Ce-UiO-66 particles grew in-situ on vermiculite; then, Ce-UiO-66 particles were activated by ultraviolet irradiation. The vermiculite absorbed visible light with a narrow band gap, and transferred photogenerated electrons to the active sites on Ce-UiO-66. Moreover, the lamella structure of vermiculite protected Ce-UiO-66 during photocatalytic process. Therefore, with only 45.92 wt% of Ce-UiO-66, the nitrogen fixation performance of VMCeact was 2.29 times that of pure activated Ce-UiO-66 particles under 455 nm light irradiation (apparent quantum efficiency of 4.49%), and retained at least 96.05% performance after 7 × 24 h of photocatalytic reaction. This cost-reduced, efficient and stable photocatalyst has the opportunity to facilitate environmentally friendly ammonia production.
The alkaline hydrogen evolution reaction (HER) is a crucial process for sustainable hydrogen production, yet it requires efficient and stable electrocatalysts to overcome the high activation energy barrier. The article discusses a novel strategy for enhancing the performance of Ni-Fe layered double hydroxide (Ni-Fe LDH) in the alkaline HER by modifying it with a frustrated Lewis acid-base pair (FLP) constructed through vacancy engineering. The study found that the modified Ni-Fe LDH exhibited improved alkaline HER performance. Density functional theory (DFT) calculations demonstrate that the introduction of FLP can activate water and protons more efficiently than monometallic sites, thus reducing the alkaline HER energy barrier and overpotential. In HER under alkaline conditions, the Volmer step involves an additional hydrolysis dissociation compared to acidic conditions, which is one of the factors contributing to the slow reaction kinetics. This paper demonstrates that FLPs can alter the rate-determining step in alkaline HER from the Volmer step to a step with a lower energy barrier, more suitable for hydrogen desorption. The work provides new insights into the role of FLPs in regulating the mechanism and kinetics of HER and opens a new direction for the design and optimization of LDH-based and other electrocatalysts.
Plants play a crucial role in maintaining ecological balance and biodiversity. However, plant health is easily affected by environmental stresses. Hence, the rapid and precise monitoring of plant health is crucial for global food security and ecological balance. Currently, traditional detection strategies for monitoring plant health mainly rely on expensive equipment and complex operational procedures, which limit their widespread application. Fortunately, near-infrared (NIR) fluorescence and surface-enhanced Raman scattering (SERS) techniques have been recently highlighted in plants. NIR fluorescence imaging holds the advantages of being non-invasive, high-resolution and real-time, which is suitable for rapid screening in large-scale scenarios. While SERS enables highly sensitive and specific detection of trace chemical substances within plant tissues. Therefore, the complementarity of NIR fluorescence and SERS modalities can provide more comprehensive and accurate information for plant disease diagnosis and growth status monitoring. This article summarizes these two modalities in plant applications, and discusses the advantages of multimodal NIR fluorescence/SERS for a better understanding of a plant's response to stress, thereby improving the accuracy and sensitivity of detection.
Aqueous zinc-based energy storage devices (ZESDs) have garnered considerable interest because of their high specific capacity, abundant zinc reserves, excellent safety, and environmental friendliness. In recent years, various types of boron, nitrogen co-doped carbon (BNC) materials have been developed to improve electrochemical performance of ZESDs. To promote the advancement of these technologies, we herein give a comprehensive review of the progress in BNC materials for ZESDs. The different synthetic methods employed in the preparation of BNC materials, including direct carbonization, template method, chemical vapor deposition, hydrothermal method, etc., are summarized. These methods play a vital role in tailoring the structure, composition, and properties of BNC materials to optimize their performance in energy storage applications. Furthermore, some key achievements of BNC materials in zinc-air batteries and zinc-ion hybrid supercapacitors are elaborated. Lastly, future challenges and development directions of BNC materials in ZESDs are prospected. This comprehensive review could serve as a valuable resource in the energy storage field, providing insights into the potential of BNC materials in zinc-based energy storage technologies.
Iron-porphyrin metal-organic frameworks (MOFs) have emerged as a remarkable class of semiconductors with adjustable photoelectrical properties and peroxidase-mimicking activities, yet their full potential remains largely unexplored. The organic photoelectrochemical transistor (OPECT) has been proven to be a prominent platform for diverse applications. Herein, iron-porphyrin MOFs, as bifunctional photo-gating module and horseradish peroxidase-mimicking nanozyme, is explored for novel OPECT bioanalysis. Exemplified by alpha-fetoprotein (AFP)-dependent sandwich immunorecognition and therein glucose oxidase (GOx)-generated H2O2 to etch CdS quantum dots on the surface of iron-porphyrin MOFs, this OPECT bioanalysis achieved high-performance AFP detection with a low detection limit of 24 fg/mL. This work featured a bifunctional iron-porphyrin MOFs gated OPECT, which is envisioned to inspire more interest in developing the diverse MOFs-nanozymes toward novel optoelectronics and beyond.
Photocatalytic NO removal is regarded as an attractive strategy to reduce NO pollution in the air, but the lack of efficient and stable catalysts impedes its applications. Herein, we report on developing Ti3C2 supported on N-defective g-C3N5 nanosheets (CNX/TC) as an efficient photocatalyst toward NO removal. It is noteworthy that TC changed from crystal structure to amorphous structure during the photocatalytic process. Due to the existence of N vacancies and amorphous structure, the designed CNX/TC composites possess abundant unsaturated sites for adsorption and activation of O2 and NO, thus facilitating the removal of NO and inhibiting the generation of NO2. The as-prepared CNX/TC-2% shows the best activity for NO removal and inhibits toxic NO2 generation. The removal rate of NO is up to 48%, which is about 2 and 4 times higher than those of pure CNX and CN, respectively. In addition, the in situ diffused reflection Fourier transform infrared spectroscopy was used to investigate the NO transfer pathway during the photocatalytic process. This work might provide new insights into the catalytic role of N-defect and amorphous, inspiring the rational design of catalysts in the field of photocatalytic NO removal.
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