Abstract
Nonnoble metal catalysts are low-cost alternatives to Pt for the oxygen reduction reactions (ORRs), which have been studied for various applications in electrocatalytic systems. Among them, ...transition metal complexes, characterized by a redox-active single-metal-atom with biomimetic ligands, such as pyrolyzed cobalt–nitrogen–carbon (Co–N
x
/C), have attracted considerable attention. Therefore, we reported the ORR mechanism of pyrolyzed Vitamin B12 using operando X-ray absorption spectroscopy coupled with electrochemical impedance spectroscopy, which enables operando monitoring of the oxygen binding site on the metal center. Our results revealed the preferential adsorption of oxygen at the Co
2+
center, with end-on coordination forming a Co
2+
-oxo species. Furthermore, the charge transfer mechanism between the catalyst and reactant enables further Co–O species formation. These experimental findings, corroborated with first-principle calculations, provide insight into metal active-site geometry and structural evolution during ORR, which could be used for developing material design strategies for high-performance electrocatalysts for fuel cell applications.
Single‐atom catalysts (SACs) have shown great potential in the electrochemical oxygen reduction reaction (ORR) toward hydrogen peroxide (H2O2) production. However, current studies are mainly focused ...on 3d transition‐metal SACs, and very little attention has been paid to 5d SACs. Here, a new kind of W SAC anchored on a porous O, N‐doped carbon nanosheet (W1/NO‐C) is designed and prepared via a simple coordination polymer‐pyrolysis method. A unique local structure of W SAC, terdentate W1N1O2 with the coordination of two O atoms and one N atom, is identified by the combination of aberration‐corrected scanning transmission electron microscopy, X‐ray photoelectron spectroscopy and X‐ray absorption fine structure spectroscopy. Remarkably, the as‐prepared W1/NO‐C catalyzes the ORR via a 2e– pathway with high onset potential, high H2O2 selectivity in the wide potential range, and excellent operation durability in 0.1 m KOH solution, superior to most of state‐of‐the‐art H2O2 electrocatalysts ever reported. Theoretical calculations reveal that the C atoms adjacent to O in the W1N1O2‐C moiety are the most active sites for the 2e– ORR to H2O2 with the optimal binding energy of the HOO* intermediate. This work opens up a new opportunity for the development of high‐performance W‐based catalysts for electrochemical H2O2 production.
A new kind of tungsten single atom catalyst anchored on a porous O, N‐doped carbon nanosheet (W1/NO‐C) is reported as an exceptional 2e– ORR electrocatalyst for H2O2 electrosynthesis, which originates from a unique terdentate W1N1O2 structure with the coordination of two O atoms and one N atom as demonstrated by the combined experimental analysis and theoretical calculations.
A simple, green, novel, time-efficient, and potentially cost-effective water activation method was employed to enhance the electrochemical activity of graphite felt (GF) electrodes for vanadium redox ...flow batteries (VRFBs). The GF electrode prepared with a water vapor injection time of 5 min at 700 °C exhibits the highest electrochemical activity for the VO2+/VO2+ couple among all the tested electrodes. This is attributed to the small, controlled amount of water vapor that was introduced producing high contents of oxygen-containing functional groups, such as OH groups, on the surface of the GF fibers, which are known to be electrochemically active sites for vanadium redox reactions. Charge–discharge tests further confirm that only 5 min of GF water activation is required to improve the efficiency of the VRFB cell. The average coulombic efficiency, voltage efficiency, and energy efficiency are 95.06%, 87.42%, and 83.10%, respectively, at a current density of 50 mA cm-2. These voltage and energy efficiencies are determined to be considerably higher than those of VRFB cells assembled using heat-treated GF electrodes without water activation and pristine GF electrodes.
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•The effect of water activation on the electrochemical activity of GF is investigated.•A high content of oxygen-containing groups improves the performance of VRFB.•Improved wettability due to increased surface-active oxygen functional groups.•WA-GF-5 min improves battery energy efficiency from 69.84% to 78.12% at 80 mA cm-2.•WA-GF-5 min acts as more powerful positive electrode for the VO2+/VO2+ redox couple.
Current reported smartphone spectrometers are only used to monitor or measure one sample at a time. For the first time, we demonstrate a multichannel smartphone spectrometer (MSS) as an optical ...biosensor that can simultaneously optical sense multiple samples. In this work, we developed a novel method to achieve the multichannel optical spectral sensing with nanometer resolution on a smartphone. A 3D printed cradle held the smartphone integrated with optical components. This optical sensor performed accurate and reliable spectral measurements by optical intensity changes at specific wavelength or optical spectral shifts. A custom smartphone multi-view App was developed to control the optical sensing parameters and to align each sample to the corresponding channel. The captured images were converted to the transmission spectra in the visible wavelength range from 400nm to 700nm with the high resolution of 0.2521nm per pixel. We validated the performance of this MSS via measuring the concentrations of protein and immunoassaying a type of human cancer biomarker. Compared to the standard laboratory instrument, the results sufficiently showed that this MSS can achieve the comparative analysis detection limits, accuracy and sensitivity. We envision that this multichannel smartphone optical biosensor will be useful in high-throughput point-of-care diagnostics with its minimizing size, light weight, low cost and data transmission function.
•A multichannel smartphone spectrometer for high-throughput POC is demonstrated.•A customized prism array fabricated by using hybrid manufacturing process is used.•High accuracy detection of protein and a cancer biomarker is presented.•The sensitivity is comparable to that of the laboratory instrument.•The total cost of this multichannel optical biosensor is less than $ 150 USD.
Identifying real active sites and understanding the mechanism of oxygen evolution reaction (OER) are still a big challenge today for developing efficient electrochemical catalysts in renewable energy ...technologies. Here, using a combined in situ/operando experiments and theory, the catalytic mechanism of the ordered OER active Co and Ir ions in Sr2CoIrO6−δ is studied, which exhibits an unprecedented low overpotential 210 mV to achieve 10 mA cm–2, ranking the highest performance among perovskite‐based solid‐state catalysts. Operando X‐ray absorption spectroscopies as a function of applied voltage indicates that Ir4+ ion is gradually converted into extremely high‐valence Ir5+/6+, while the part of Co3+ ion is transferred into Co4+ under OER process. Density functional theory calculations explicitly reveal the order Co‐O‐Ir network as an origin of ultrahigh OER activity. The work opens a promising path to overcome the sluggish kinetics of OER bottleneck for water splitting via proper arrangements of the multi‐active sites in catalyst.
Operando experimental observation of a gradual oxidation state transition from Ir4+ to Ir5+ and further to Ir6+ and theoretical simulation expatiates the origin of ultrafast electrocatalytic water oxidation of the Sr2CoIrO6−δ catalyst with Co‐O‐Ir ordered arrangement.
The combination of conventional transition‐metal‐catalyzed coupling (2 e− process) and photoredox catalysis (1 e− process) has emerged as a powerful approach to catalyze difficult cross‐coupling ...reactions under mild reaction conditions. Reported is a palladium carbodicarbene (CDC) complex that mediates both a Suzuki–Miyaura coupling and photoredox catalysis for C−N bond formation upon visible‐light irradiation. These two catalytic pathways can be combined to promote both conventional transition‐metal‐catalyzed coupling and photoredox catalysis to mediate C−H arylation under ambient conditions with a single catalyst in an efficient one‐pot process.
A one, two combo: The combination of conventional transition‐metal‐catalyzed coupling (2 e− process) and photoredox catalysis (1 e− process) has emerged as a powerful approach to catalyze difficult cross‐coupling reactions under mild reaction conditions. Reported is the use of a single palladium carbodicarbene (CDC) complex that mediates both a Suzuki–Miyaura coupling and photoredox catalysis for C−N bond formation upon visible‐light irradiation.
Background
The transoral approach and the bilateral axillo-breast approach (BABA) are remote access approaches for endoscopic thyroidectomy. Both follow a symmetric design and use CO
2
insufflation ...to maintain the working space. The outcome differences between the techniques are rarely compared in the literature.
Methods
All patients who underwent endoscopic transoral (
n
= 72) and BABA (
n
= 63) thyroidectomy between October 2018 and August 2020 by a single surgeon were retrospectively reviewed. The following peri-operative data were collected and compared: operative time, blood loss, postoperative drainage amount, hospital stay, pain score, number of retrieved lymph nodes, and complications.
Results
Patients in the transoral group were younger (44.7 vs. 49.3 years,
p
= 0.022) and had smaller tumors (2.4 vs. 2.8 cm,
p
= 0.020) than those in the BABA group. The operative times were significantly longer in the transoral group than in the BABA group (lobectomy, 194.1 vs. 177.0 min,
p
= 0.026; total thyroidectomy, 246.0 vs. 214.3 min,
p
= 0.042). Nevertheless, the time difference became insignificant after completing the initial 20 cases of transoral thyroidectomy. The drainage fluid collected after the surgery was serosanguinous, and a lower drainage volume was observed in the transoral group than that in the BABA group (64.9 vs. 78.5 ml,
p
= 0.017). However, there was no significant difference regarding the blood loss, hospital stay, postoperative pain score, and lymph nodes retrieved. The rate of postoperative complications, such as hypoparathyroidism and vocal cord palsy was comparable between the two groups.
Conclusions
Transoral approach and BABA are comparable with regard to surgical outcomes. Selected patients may choose either technique based on their preferences.
As a key parameter impacting functional and structural heterogeneity, protein glycosylation is a critical quality attribute for antibody biotherapeutic manufacturing. The glycan patterns on ...recombinant antibodies, particularly on the conserved fragment crystallizable (Fc) region, can have significant effects on an antibody's functional activities including clearance rate, antibody‐dependent cellular cytotoxicity (ADCC), complement‐dependent cytotoxicity (CDC), and anti‐inflammatory activity. In this review, we examined specific glycan attachments (fucosylation, sialylation, galactosylation, high‐mannose, and bisecting glycans) and their importance to antibody properties. Next, we summarized the recent and current achievements on controlling antibody glycoforms in Chinese hamster ovary (CHO) and other mammalian cells through multiple strategies including genetic engineering, protein engineering, media modification, and other emerging technologies. Further, the impact of one carbohydrate modification on other glycan structures is also described. Finally, approaches to generate desirable homogenous glycan profiles on antibodies are also detailed. By applying multiple complementary intracellular and extracellular strategies, biotechnologists are well on their ways to precisely tuning antibody glycoforms emerging from bioreactors in the coming decades.
Recent mammalian cell antibody glycoengineering strategies, which play a critical role on effector functions, are reviewed. Defucosylation increases antibody‐dependent cellular cytotoxicity (ADCC), α‐2,6‐sialylation promotes anti‐inflammatory activity, and high‐mannose glycans cause faster serum clearance. Pros and cons of glycoengineering approaches are described including genetic engineering, media modification, and protein engineering. The combination of multiple intracellular and extracellular strategies can be used to optimize glycan structures that cannot be achieved by a single approach and advance a more favorable glycoprotein therapeutic drug.
Abstract
Designing efficient catalyst for the oxygen evolution reaction (OER) is of importance for energy conversion devices. The anionic redox allows formation of O-O bonds and offers higher OER ...activity than the conventional metal sites. Here, we successfully prepare LiNiO
2
with a dominant 3
d
8
L
configuration (
L
is a hole at O 2
p
) under high oxygen pressure, and achieve a double ligand holes 3
d
8
L
2
under OER since one electron removal occurs at O 2
p
orbitals for Ni
III
oxides. LiNiO
2
exhibits super-efficient OER activity among LiMO
2
,
R
MO
3
(M = transition metal,
R
= rare earth) and other unary 3d catalysts. Multiple in situ/operando spectroscopies reveal Ni
III
→Ni
IV
transition together with Li-removal during OER. Our theory indicates that Ni
IV
(3
d
8
L
2
) leads to direct O-O coupling between lattice oxygen and *O intermediates accelerating the OER activity. These findings highlight a new way to design the lattice oxygen redox with enough ligand holes created in OER process.
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