The anode oxygen evolution reaction (OER) is known to largely limit the efficiency of electrolyzers owing to its sluggish kinetics. While crystalline metal oxides are promising as OER catalysts, ...their amorphous phases also show high activities. Efforts to produce amorphous metal oxides have progressed slowly, and how an amorphous structure benefits the catalytic performances remains elusive. Now the first scalable synthesis of amorphous NiFeMo oxide (up to 515 g in one batch) is presented with homogeneous elemental distribution via a facile supersaturated co‐precipitation method. In contrast to its crystalline counterpart, amorphous NiFeMo oxide undergoes a faster surface self‐reconstruction process during OER, forming a metal oxy(hydroxide) active layer with rich oxygen vacancies, leading to superior OER activity (280 mV overpotential at 10 mA cm−2 in 0.1 m KOH). This opens up the potential of fast, facile, and scale‐up production of amorphous metal oxides for high‐performance OER catalysts.
Amorphous NiFeMo oxide (up to 515 g one batch) with homogeneous elemental distribution was synthesized through a facile supersaturated co‐precipitation method. The amorphous NiFeMo oxide undergoes rapid surface self‐reconstruction during OER that forms a metal oxy(hydroxide) active layer with oxygen vacancies, enabling efficient OER catalysis.
Bimetallic metal–organic frameworks are rationally synthesized as templates and employed for porous carbons with retained morphology, high graphitization degree, hierarchical porosity, high surface ...area, CoNx moiety and uniform N/Co dopant by pyrolysis. The optimized carbon with additional phosphorus dopant exhibits excellent electrocatalytic performance for the oxygen reduction reaction, which is much better than the benchmark Pt/C in alkaline media.
It remains highly desired but a great challenge to achieve atomically dispersed metals in high loadings for efficient catalysis. Now porphyrinic metal–organic frameworks (MOFs) have been synthesized ...based on a novel mixed‐ligand strategy to afford high‐content (1.76 wt %) single‐atom (SA) iron‐implanted N‐doped porous carbon (FeSA‐N‐C) via pyrolysis. Thanks to the single‐atom Fe sites, hierarchical pores, oriented mesochannels and high conductivity, the optimized FeSA‐N‐C exhibits excellent oxygen reduction activity and stability, surpassing almost all non‐noble‐metal catalysts and state‐of‐the‐art Pt/C, in both alkaline and more challenging acidic media. More far‐reaching, this MOF‐based mixed‐ligand strategy opens a novel avenue to the precise fabrication of efficient single‐atom catalysts.
Iron islands: Based on a mixed‐ligand strategy, a porphyrinic MOF was pyrolyzed to afford high‐content single‐atom iron‐implanted N‐doped porous carbon (FeSA‐N‐C). Thanks to the FeSA sites, hierarchical pores, oriented mesochannels, and high conductivity, FeSA‐N‐C exhibits excellent oxygen reduction activity and stability, surpassing almost all non‐noble‐metal catalysts and Pt/C, in both alkaline and the more challenging acidic media.
SiOx is proposed as one of the most promising anodes for Li‐ion batteries (LIBs) for its advantageous capacity and stable Li uptake/release electrochemistry, yet its practical application is still a ...big challenge. Here encapsulation of SiOx nanoparticles into conductive graphene bubble film via a facile and scalable self‐assembly in solution is shown. The SiOx nanoparticles are closely wrapped in multilayered graphene to reconstruct a flake‐graphite‐like macrostructure, which promises uniform and agglomeration‐free distribution of SiOx in the carbon while ensures a high mechanical strength and a high tap density of the composite. The composites present unprecedented cycling stability and excellent rate capabilities upon Li storage, rendering an opportunity for its anode use in the next‐generation high‐energy LIBs.
SiOx nanoparticles are closely wrapped in multilayered graphene to reconstruct a macrostructure resembling flake graphite, which promises agglomeration‐free distribution of SiOx in the bulk while ensuring a high mechanical strength and a high tap density of the bubble film. By taking the advantages of the graphene network, the composites present unprecedented cycling stability and excellent rate capabilities upon Li storage.
The exploitation of photocatalysts that harvest solar spectrum as broad as possible remains a high‐priority target yet grand challenge. In this work, for the first time, metal–organic framework (MOF) ...composites are rationally fabricated to achieve broadband spectral response from UV to near‐infrared (NIR) region. In the core–shell structured upconversion nanoparticles (UCNPs)‐Pt@MOF/Au composites, the MOF is responsive to UV and a bit visible light, the plasmonic Au nanoparticles (NPs) accept visible light, whereas the UCNPs absorb NIR light to emit UV and visible light that are harvested by the MOF and Au once again. Moreover, the MOF not only facilitates the generation of “bare and clean” Au NPs on its surface and realizes the spatial separation for the Au and Pt NPs, but also provides necessary access for catalytic substrates/products to Pt active sites. As a result, the optimized composite exhibits excellent photocatalytic hydrogen production activity (280 µmol g−1 h−1) under simulated solar light, and the involved mechanism of photocatalytic H2 production under UV, visible, and NIR irradiation is elucidated. Reportedly, this is an extremely rare study on photocatalytic H2 production by light harvesting in all UV, visible, and NIR regions.
Novel broadband spectrum‐responsive metal–organic framework (MOF) composites, upconversion nanoparticles‐Pt@MOF/Au, are fabricated based on plasmonic and upconversion effects. Strikingly, the composites exhibit considerable photocatalytic hydrogen production activities under UV, visible, or even near‐infrared light irradiation, which represents the first work reporting hydrogen production photocatalysts with considerable activity toward all these three regions of light irradiation.
Abstract
Single-atom catalysts (SACs) have sparked broad interest recently while the low metal loading poses a big challenge for further applications. Herein, a dual protection strategy has been ...developed to give high-content SACs by nanocasting SiO
2
into porphyrinic metal–organic frameworks (MOFs). The pyrolysis of SiO
2
@MOF composite affords single-atom Fe implanted N-doped porous carbon (Fe
SA
–N–C) with high Fe loading (3.46 wt%). The spatial isolation of Fe atoms centered in porphyrin linkers of MOF sets the first protective barrier to inhibit the Fe agglomeration during pyrolysis. The SiO
2
in MOF provides additional protection by creating thermally stable FeN
4
/SiO
2
interfaces. Thanks to the high-density Fe
SA
sites, Fe
SA
–N–C demonstrates excellent oxygen reduction performance in both alkaline and acidic medias. Meanwhile, Fe
SA
–N–C also exhibits encouraging performance in proton exchange membrane fuel cell, demonstrating great potential for practical application. More far-reaching, this work grants a general synthetic methodology toward high-content SACs (such as Fe
SA
, Co
SA
, Ni
SA
).
Peroxisomes account for ~35% of total H2O2 generation in mammalian tissues. Peroxisomal ACOX1 (acyl‐CoA oxidase 1) is the first and rate‐limiting enzyme in fatty acid β‐oxidation and a major producer ...of H2O2. ACOX1 dysfunction is linked to peroxisomal disorders and hepatocarcinogenesis. Here, we show that the deacetylase sirtuin 5 (SIRT5) is present in peroxisomes and that ACOX1 is a physiological substrate of SIRT5. Mechanistically, SIRT5‐mediated desuccinylation inhibits ACOX1 activity by suppressing its active dimer formation in both cultured cells and mouse livers. Deletion of SIRT5 increases H2O2 production and oxidative DNA damage, which can be alleviated by ACOX1 knockdown. We show that SIRT5 downregulation is associated with increased succinylation and activity of ACOX1 and oxidative DNA damage response in hepatocellular carcinoma (HCC). Our study reveals a novel role of SIRT5 in inhibiting peroxisome‐induced oxidative stress, in liver protection, and in suppressing HCC development.
Synopsis
This study reveals a role for SIRT5 in regulating peroxisomal H2O2 and ROS homeostasis and indicates its potential function in liver protection and hepatocellular carcinoma suppression.
SIRT5 is localized in peroxisomes where it controls H2O2 metabolism.
SIRT5‐mediated desuccinylation inhibits ACOX1 activity by suppressing its active dimer formation.
SIRT5 downregulation increases ACOX1 activity and oxidative DNA damage response in HCC.
This study reveals a role for SIRT5 in regulating peroxisomal H2O2 and ROS homeostasis and indicates its potential function in liver protection and hepatocellular carcinoma suppression.
Superelastic carbon aerogels have been widely explored by graphitic carbons and soft carbons. These soft aerogels usually have delicate microstructures with good fatigue resistance but ultralow ...strength. Hard carbon aerogels show great advantages in mechanical strength and structural stability due to the sp3‐C‐induced turbostratic “house‐of‐cards” structure. However, it is still a challenge to fabricate superelastic hard carbon‐based aerogels. Through rational nanofibrous structural design, the traditional rigid phenolic resin can be converted into superelastic hard carbon aerogels. The hard carbon nanofibers and abundant welded junctions endow the hard carbon aerogels with robust and stable mechanical performance, including superelasticity, high strength, extremely fast recovery speed (860 mm s−1), low energy‐loss coefficient (<0.16), long cycle lifespan, and heat/cold‐endurance. These emerging hard carbon nanofiber aerogels hold a great promise in the application of piezoresistive stress sensors with high stability and wide detection range (50 kPa), as well as stretchable or bendable conductors.
A family of hard carbon aerogels with nanofibrous structure templated by various nanofibers is fabricated, displaying robust and stable mechanical performances, including high strength, extremely fast recovery speed (860 mm s−1), and ultralow energy loss coefficient (<0.16). After being compressed for 104 cycles (50% strain), they show only ≈2% plastic deformation and retain ≈93% stress.
Energy efficient buildings require materials with a low thermal conductivity and a high fire resistance. Traditional organic insulation materials are limited by their poor fire resistance and ...inorganic insulation materials are either brittle or display a high thermal conductivity. Herein we report a mechanically resilient organic/inorganic composite aerogel with a thermal conductivity significantly lower than expanded polystyrene and excellent fire resistance. Co‐polymerization and nanoscale phase separation of the phenol‐formaldehyde‐resin (PFR) and silica generate a binary network with domain sizes below 20 nm. The PFR/SiO2 aerogel can resist a high‐temperature flame without disintegration and prevents the temperature on the non‐exposed side from increasing above the temperature critical for the collapse of reinforced concrete structures.
Fire not starter: Taking advantage of a co‐polymerization strategy an organic–inorganic binary network hybrid aerogel with a nanoscale homogeneity can be prepared. The phenol‐formaldehyde‐resin/SiO2 aerogel is mechanically resilient and has a thermal conductivity significantly lower than expanded polystyrene and excellent fire resistance.
The general synthesis and control of the coordination environment of single‐atom catalysts (SACs) remains a great challenge. Herein, a general host–guest cooperative protection strategy has been ...developed to construct SACs by introducing polypyrrole (PPy) into a bimetallic metal–organic framework. As an example, the introduction of Mg2+ in MgNi‐MOF‐74 extends the distance between adjacent Ni atoms; the PPy guests serve as N source to stabilize the isolated Ni atoms during pyrolysis. As a result, a series of single‐atom Ni catalysts (named NiSA‐Nx‐C) with different N coordination numbers have been fabricated by controlling the pyrolysis temperature. Significantly, the NiSA‐N2‐C catalyst, with the lowest N coordination number, achieves high CO Faradaic efficiency (98 %) and turnover frequency (1622 h−1), far superior to those of NiSA‐N3‐C and NiSA‐N4‐C, in electrocatalytic CO2 reduction. Theoretical calculations reveal that the low N coordination number of single‐atom Ni sites in NiSA‐N2‐C is favorable to the formation of COOH* intermediate and thus accounts for its superior activity.
A host–guest cooperative protection strategy has been developed for constructing single‐atom catalysts (SACs), extending the range of available precursors from nitrogenous to non‐nitrogenous MOFs. The obtained Ni‐SACs (NiSA‐Nx‐C; x=2, 3, 4) at different pyrolysis temperatures feature varying nitrogen coordination numbers. The best of these catalysts, NiSA‐N2‐C, shows superior activity and selectivity in CO2 electroreduction.
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