Metal organic frameworks (MOFs), an emerging class of nanoporous crystalline materials, have become increasingly attractive for solar energy applications. In this work, we report a newly designed mixed-node MOF catalyst, Co x Fe1–x -MOF-74 (0 < x ≤ 1), which acts as a highly efficient electrocatalyst for oxygen evolution reaction (OER) in alkaline solution with remarkably low overpotential (280 mV at a current density of 10 mA/cm2), small Tafel slope (56 mV/dec), and high faradic efficiency (91%) and can deliver a current density of 20 mA/cm2 at 1.58 V for overall water splitting. Moreover, using the combination of multiple spectroscopic methods, including X-ray absorption, electron spin resonance, and X-ray photoelectron spectroscopy, etc., we unraveled the mechanistic origin of the enhanced catalytic performance of Co x Fe1–x -MOF-74 compared to its single-metal counterparts. We show the mixed-node MOF can provide more open metal sites and an enhanced electron-rich environment, which facilitates efficient charge transfer and results in significantly enhanced OER activity.
Electrochemical activation is an effective and simple method to obtain in-situ surface modification of MOF materials away from thermal decomposition. However, the impact of the rate and related phase transformation on OER intrinsic activity during the electrochemical activation process is often overlooked. Herein, we synthesized a kind of Co-MOF with a unique crystal structure in which the center metals were coordinated with the oxygen and nitrogen atoms from two water molecules and organic linkers. The bond strength between the center metals and the coordinated water molecules can be modulated by introducing Fe into Co-MOF, causing the expedited electrochemical activation. First-principles calculations suggest the electronic state of cobalt in CoFe-MOF can be modified to alter the free energy of adsorbed intermediates. Therefore, the obtained electrocatalyst possesses the optimal OER intrinsic activity, showing a low overpotential of 265 mV at 10 mA cm–2, a small Tafel slope of 44 mV dec–1, and a long-term electrochemical durability with a period of 40 h. The findings are expected to help understand the fundamental principles of electrochemical activation.
Caveolin-1 (Cav-1) is known to participate in many diseases, but its roles in alcoholic liver injury remain unknown. In the present study, we aimed to explore the roles of Cav-1 in protecting hepatocytes from ethanol-mediated nitrosative injury. We hypothesized that Cav-1 could attenuate ethanol-mediated nitrosative stress and liver damage through regulating epidermal growth factor receptor/signal transducer and activator of transcription 3/inducible nitric oxide synthase (EGFR/STAT3/iNOS)-signaling cascades. Ethanol-fed mice had time-and dose-dependent increases of Cav-1 in serum and liver with peak increase at 12 hours. Compared to wild-type mice, Cav-1 deficiency mice revealed higher expression of iNOS, higher levels of nitrate/nitrite and peroxynitrite, and had more serious liver damage, accompanied with higher levels of cleaved caspase-3 and apoptotic cell death in liver, and higher levels of alanine aminotransferase and aspartate aminotransferase in serum. Furthermore, the results revealed that the ethanolmediated Cav-1 increase was in an extracellular signal-regulated kinase-dependent manner, and Cav-1 protected hepatocytes from ethanol-mediated apoptosis by inhibiting iNOS activity and regulating EGFR-and STAT3-signaling cascades. In agreement with these findings, clinical trials in human subjects revealed that serum Cav-1 level was time dependently elevated and peak concentration was observed 12 hours after binge drinking. Alcohol-induced liver lesions were negatively correlated with Cav-1 level, but positively correlated with nitrate/nitrite level, in serum of binge drinkers. Conclusions: Cav-1 could be a cellular defense protein against alcoholic hepatic injury through inhibiting reactive nitrogen species and regulating EGFR/STAT3/iNOS-signaling cascades. (HEPATOLOGY 2014;60:687-699) B inge drinking is defined as episodic excessive drinking of alcoholic beverages over a short period of time. 1 "Binge" commonly means consuming five or more standard drinks (male), or four or more drinks (female), on one occasion. Binge drinking becomes a major public health issue causing fatty liver, hypertension, neuronal damage, and so on. 2,3 Many binge drinkers are susceptible to suffer from advanced alcoholic liver diseases (ALD), including steatohepatitis, hepatic fibrosis, and cirrhosis. 3,4 Given that alcoholic liver injury has become a common health care problem, exploring underlying Abbreviations: 1400W, N-(3-(aminomethyl)benzyl)acetamidine; ADH-1, alcohol dehydrogenases class 1; ALD, alcoholic liver diseases; ALDH2, aldehyde dehydrogenase class 2; ALT, alanine aminotransferase; AST, aspartate aminotransferase; BAC, blood-alcohol concentration; Bcl-2, B-cell lymphoma 2; b.w., body weight; CAT, catalase; Cav-1, caveolin-1; EC, endothelial cell; EGFR, epidermal growth factor receptor; eNOS, endothelial nitric oxide synthase; ERK, extracellular signalregulated kinase; GSH, glutathione; GSSG, glutathione disulfide; iNOS: inducible nitric oxide synthase; KO, knockout; mRNA, messenger RNA; NO, nitric oxide; 3-NT,...
A series of hierarchical porous SnO 2 microspheres (SnO 2 -Ms) with same sizes of nanoparticles were fabricated through increasing the reaction time of the one-step hydrothermal method. Especially, these SnO 2 -Ms also have the different specific surface areas and pores sizes. When they are applied in sintering type thick film gas sensors, through comparing the gas-sensing property of the as-prepared SnO 2 -Ms, it can clearly demonstrate that the surface chemical reaction (SCR) control of the sensing properties of sensors is gradually replaced by the gas diffusion control with the operation temperature (T o ) increasing. For the first time, this dually control is discovered through contrast experiment. According to the testing results, the sensing mechanism of sensors can be explained by many factors, such as the reaction rate constant of the SCR, the Knudsen diffusion coefficient of the target gas, the T o , the specific surface area, the pore size and the change of the H 2 O, etc. A pore canal model and a hollow sphere model are introduced, which can effectively explain the sensing mechanism of gas sensors. This discovery can make up for the inadequacy of the surface-control and the diffusion-control theory, and expound their interrelation. This discovery also provides a novel strategy for studying the sensing mechanism of sensors, which is expected to open up exciting opportunities for improving the sensing properties of the gas-sensing materials and studying some gas-solid catalytic phenomena.
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