The proper structure design and defect engineering are of essential importance to develop advanced electrocatalysts for the oxygen reduction reaction (ORR), which is a critical reaction in both ...fundamental science and industrial applications. Herein, a three‐dimensional carbon electrocatalyst is prepared by in‐situ linking carbon polyhedrons with nanosheets through high‐temperature pyrolysis of metal‐organic frameworks (MOFs) confined in a salt‐sealed reactor. In the transformation to polyhedrons, the organic species partially decompose and form carbon nanosheets due to being confined in the salt reactor. The in ‐situ‐formed carbon nanosheets surround the carbon polyhedrons to form a 3D carbon network. Due to the confinement effect, the transformation of MOFs to carbon networks in the salt reactor is of high yield without significant loss of active carbon species, which would enhance the electron and mass transport for electrocatalysis. More interestingly, the as‐prepared 3D nanosheet‐linked‐polyhedron carbon (NLPC) is defect‐rich with high N‐doping levels and enriched active sites for electrocatalysis. With enhanced mass, electron transport, and enriched active sites, the material shows excellent activity as ORR electrocatalyst which is even comparable with Pt/C. The primary zinc‐air batteries assembled by the NLPC as the cathode also show outstanding performance.
3D carbon electrocatalysts is constructed by in situ linking carbon polyhedrons with nanosheets from metal‐organic frameworks in a salt (NaCl) confined reactor. The 3D macroscopic structure contributes to the enhanced mass diffusion, the nanosheet linking increases the electronic conductivity, and the high N doping and the rich defects provide abundant active sites for oxygen reduction reaction.
Water splitting has been considered as one of the most prospective technologies for enhancing sustainable output of hydrogen and reducing the release of carbon dioxide in the 21st century. Much ...attention has been paid to designing optimal electrocatalysts for water splitting, which includes the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). To date, the most effective water splitting electrocatalysts are still Pt based and Ir or Ru group noble metal materials, which can significantly improve the current density with the presence of a low overpotential. As alternatives to noble metals electrocatalysts, a series of studies have been carried out for cobalt-based electrocatalysts on the strengths of non-noble metal properties over the past years. However, the defect engineering of cobalt-based materials for the water splitting process has not been explained systematically. Herein, we summarize various kinds of defects and their functions based on Co-based materials for OER and HER. The principles of how various defects improved electrocatalytic performance are introduced clearly; then, the vacancies (included anion and cation vacancies) and heteroatomic doping (included nonmetal and metal atomic doping) were introduced systematically. Furthermore, we especially highlight several defect modification electrocatalysts. Finally, difficulties of defects engineering and the future research directions for Co-implicated electrocatalysts are proposed.
The exact role of a defect structure on transition metal compounds for electrocatalytic oxygen evolution reaction (OER), which is a very dynamic process, remains unclear. Studying the ...structure–activity relationship of defective electrocatalysts under operando conditions is crucial for understanding their intrinsic reaction mechanism and dynamic behavior of defect sites. Co3O4 with rich oxygen vacancy (VO) has been reported to efficiently catalyze OER. Herein, we constructed pure spinel Co3O4 and VO-rich Co3O4 as catalyst models to study the defect mechanism and investigate the dynamic behavior of defect sites during the electrocatalytic OER process by various operando characterizations. Operando electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) implied that the VO could facilitate the pre-oxidation of the low-valence Co (Co2+, part of which was induced by the VO to balance the charge) at a relatively lower applied potential. This observation confirmed that the VO could initialize the surface reconstruction of VO–Co3O4 prior to the occurrence of the OER process. The quasi-operando X-ray photoelectron spectroscopy (XPS) and operando X-ray absorption fine structure (XAFS) results further demonstrated the oxygen vacancies were filled with OH• first for VO–Co3O4 and facilitated pre-oxidation of low-valence Co and promoted reconstruction/deprotonation of intermediate Co–OOH•. This work provides insight into the defect mechanism in Co3O4 for OER in a dynamic way by observing the surface dynamic evolution process of defective electrocatalysts and identifying the real active sites during the electrocatalysis process. The current finding would motivate the community to focus more on the dynamic behavior of defect electrocatalysts.
Electrocatalysis is dominated by reaction at the solid–liquid–gas interface; surface properties of electrocatalysts determine the electrochemical behavior. The surface charge of active sites on ...catalysts modulate adsorption and desorption of intermediates. However, there is no direct evidence to bridge surface charge and catalytic activity of active sites. Defects (active sites) were created on a HOPG (highly oriented pyrolytic graphite) surface that broke the intrinsic sp2‐hybridization of graphite by plasma, inducing localization of surface charge onto defective active sites, as shown by scanning ion conductance microscopy (SICM) and Kelvin probe force microscopy (KPFM). An electrochemical test revealed enhanced intrinsic activity by the localized surface charge. DFT calculations confirmed the relationship between surface charge and catalytic activity. This work correlates surface charge and catalytic activity, providing insights into electrocatalytic behavior and guiding the design of advanced electrocatalysts.
Highly oriented pyrolytic graphite (HOPG) was employed as a model to analyze the promotion of surface charge for electrocatalytic reactions. Via plasma irradiation, numerous defects are generated, which would induce charge re‐distribution on the surface of HOPG. A direct relationship between surface charge and the electrocatalytic activity is proposed.
Permian-Triassic boundary (PTB) volcanic ash beds are widely distributed in South China and were proposed to have a connection with the PTB mass extinction and the assemblage of Pangea. However, ...their source and tectonic affinity have been highly debated. We present zircon U-Pb ages, trace-element and Hf isotopic data on three new-found PTB volcanic ash beds in the western Hubei area, South China. Laser ablation inductively coupled plasma mass spectrometry U-Pb dating of zircons yields ages of 252.2±3.6 Ma, 251.6±4.9 Ma and 250.4±2.4 Ma for these three volcanic ash beds. Zircons of age c. 240-270 Ma zircons have negative εHf(t) values (-18.17 to -3.91) and Mesoproterozoic-Palaeoproterozoic two-stage Hf model ages (THf2) (1.33-2.23 Ga). Integrated with other PTB ash beds in South China, zircon trace-element signatures and Hf isotopes indicate that they were likely sourced from intermediate to felsic volcanic centres along the Simao-Indochina convergent continental margin. The Qinling convergent continental margin might be another possible source but needs further investigation. Our data support the model that strong convergent margin volcanism took place around South China during late Permian-Early Triassic time, especially in the Simao-Indochina active continental margin and possibly the Qinling active continental margin. These volcanisms overlap temporally with the PTB biocrisis triggered by the Siberian Large Igneous Province. In addition, our data argue that the South China Craton and the Simao-Indochina block had not been amalgamated with the main body of Pangea by late Permian-Early Triassic time.
Electrocatalytic water splitting is a crucial area in sustainable energy development, and the development of highly efficient bifunctional catalysts that exhibit activity toward both hydrogen ...evolution reaction (HER) and oxygen evolution reaction (OER) is of paramount importance. Co3O4 is a promising candidate catalyst, owing to the variable valence of Co, which can be exploited to enhance the bifunctional catalytic activity of HER and OER through rational adjustments of the electronic structure of Co atoms. In this study, we employed a plasma-etching strategy in combination with an in situ filling of heteroatoms to etch the surface of Co3O4, creating abundant oxygen vacancies, while simultaneously filling them with nitrogen and sulfur heteroatoms. The resulting N/S-VO-Co3O4 exhibited favorable bifunctional activity for alkaline electrocatalytic water splitting, with significantly enhanced HER and OER catalytic activity compared to pristine Co3O4. In an alkaline overall water-splitting simulated electrolytic cell, N/S-VO-Co3O4 || N/S-VO-Co3O4 showed excellent overall water splitting catalytic activity, comparable to noble metal benchmark catalysts Pt/C || IrO2, and demonstrated superior long-term catalytic stability. Additionally, the combination of in situ Raman spectroscopy with other ex situ characterizations provided further insight into the reasons behind the enhanced catalyst performance achieved through the in situ incorporation of N and S heteroatoms. This study presents a facile strategy for fabricating highly efficient cobalt-based spinel electrocatalysts incorporated with double heteroatoms for alkaline electrocatalytic monolithic water splitting.
Cobalt oxides as efficient oxygen evolution reaction (OER) electrocatalysts have received much attention because of their rich reserves and cheap cost. There are two common cobalt oxides, Co3O4 ...(spinel phase, stable but poor intrinsic activity) and CoO (rocksalt phase, active but easily be oxidatized). Constructing Co3O4/CoO heterophase can inherit both characteristic features of each component and form a heterophase interface facilitating charge transfer, which is believed to be an effective strategy in designing excellent electrocatalysts. Herein, an atomic arrangement engineering strategy is applied to improve electrocatalytic activity of Co3O4 for the OER. With the presence of oxygen vacancies, cobalt atoms at tetrahedral sites in Co3O4 can more easily diffuse into interstitial octahedral sites to form CoO phase structure as revealed by periodic density functional theory computations. The Co3O4/CoO spinel/rocksalt heterophase can be in situ fabricated at the atomic scale in plane. The overpotential to reach 10 mA cm−2 of Co3O4/CoO is 1.532 V, which is 92 mV smaller than that of Co3O4. Theoretical calculations confirm that the excellent electrochemical activity is corresponding to a decline in average p‐state energy of adsorbed‐O on the Co3O4/CoO heterophase interface. The reaction Gibbs energy barrier has been significantly decreased with the construction of the heterophase interface.
A Co3O4/CoO heterophase interface at the atomic scale is elaborately constructed by incorporating oxygen vacancies. Theoretical calculation proves that with the existence of oxygen vacancies, the energy barrier for Co atom diffusion from tetrahedron sites to neighboring interstitial octahedron sites is dramatically decreased indicating more favorable formation of CoO. With the formation of the Co3O4/CoO heterophase interface, oxygen evolution reaction activity is enhanced effectively.
Severe global climate change is proposed to be the major cause of the Permian-Triassic boundary (PTB) mass extinction, while details about the response process are still in debate. In this study, we ...present geochemical and pyrite morphological data from an Upper Permian-Lower Triassic shale succession in the Western Hubei Trough, northern South China. The stratigraphic evolutions of paleoclimate, paleoredox condition and paleosalinity are analysed. Our data support that regional tectonics, collision of the South China Craton and the North China Craton, may have played a major role in hydrographic and redox evolution of the Western Hubei Trough, suggesting anoxia may not be a worldwide cause of marine PTB biocrisis. On the other hand, an extensive comparison between marine and terrestrial successions supports that global warming in the Late Permian may have induced enhanced supply of freshwater to the ocean and the flooding of seawater across the boundary between marine and fresh to brackish waters due to sea-level rise, leading to dilution of seawater, while global cooling in the Permian-Triassic transition may have induced reduced supply of freshwater to the ocean, leading to increase of seawater paleosalinity. On the land, both global and regional climate changes may have controlled the freshwater supply to water bodies, leading to fluctuation of watermass paleosalinity. Our data support that anomalous changes of watermass paleosalinity triggered by paleoclimate changes may have played a role in the PTB biocrisis.
•Regional tectonics controlled the redox evolution of the Western Hubei Trough.•Anoxia may not be a worldwide cause of marine PTB biocrisis.•Climate-induced watermass salinity changes may play a role in the PTB biocrisis.
The development of efficient electrocatalysts for hydrogen evolution reactions is an extremely important area for the development of green and clean energy. In this work, a precursor material was ...successfully prepared via electrodeposition of two doping elements to construct a co-doped cobalt hydroxide electrocatalyst (Ru-Co(OH)
-Se). This approach was demonstrated to be an effective way to improve the performance of the hydrogen evolution reaction (HER). The experimental results show that the material exhibited a smaller impedance value and a larger electrochemically active surface area. In the HER process, the overpotential was only 109 mV at a current density of 10 mA/cm
. In addition, the doping of selenium and ruthenium effectively prevented the corrosion of the catalysts, with the (Ru-Co(OH)
-Se) material showing no significant reduction in the catalytic performance after 50 h. This synergistic approach through elemental co-doping demonstrated good results in the HER process.
The limited efficacy of chemotherapy and immunotherapy for pancreatic cancer is thought to be largely influenced by the surrounding cancer microenvironment. The hypoxic microenvironment caused by ...insufficient local blood supply is very important. However, the method to assess the level of hypoxia in the microenvironment of pancreatic cancer (PC) remains unclear.
In our research, we downloaded transcriptomic and clinicopathological data from the Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO). A prognostic model was developed using univariate and multivariate Cox regression. The ConsensuClusterPlus R package was used to consistently cluster PC samples through unsupervised clustering. Gene set variation analysis (GSVA) was performed to identify the different functional phenotypes. The CIBERSORT evaluated the infiltration status of immune cells. qRT-PCR was performed to detect the expression of genes in PC cells and tissues.
A preliminary risk model was developed to reflect the hypoxic environment of pancreatic cancer. We found that a high hypoxia risk score indicated poor long-term survival and the presence of an immunosuppressive microenvironment. In addition, based on prognostic hypoxia-related genes, 177 PC samples were divided into two subtypes. Compared with cluster 2, cluster 1 was defined as the "hypoxic subgroup". The infiltration of CD8 T cells, activated memory CD4 T cells, naive B cells, memory B cells, plasma cells, and neutrophils were lower in cluster 1, suggesting that there was significant immunosuppression in cluster 1. Beyond that, we constructed a ceRNA regulatory network composed of differentially expressed lncRNA, miRNA, and mRNA. LSAMPAS1/ hsa-miR-129-5p/S100A2 has been identified as a key ceRNA network that regulates the hypoxic environment and the prognosis of PC. Notably, in our study, qRT-PCR revealed the relative expression of LSAMP-AS1 and S100A2 was significantly upregulated in PC cells and tissue.
The hypoxia-related prognostic risk model and core ceRNA network established in our study will provide a new perspective for exploring the carcinogenic mechanism and potential therapeutic targets of pancreatic cancer.
