Well-dispersed SnO2 nanocrystals on N-doped carbon nanowires as efficient electrocatalysts for carbon dioxide reduction

The conversion of carbon dioxide into valuable organic compounds is a highly promising approach to address the energy issues and environmental problems(e.g., global warming). Herein, we presents a facile and efficient method to prepare highly dense and well-dispersed SnO2 nanocrystals on 1 D N-doped carbon nanowires as advanced catalysts for the efficient electroreduction of CO2 to formate. The ultrasmall SnO2 coated on the N-doped carbon nanowires(SnO2@N-CNW) has been synthesized via the simple hydrothermal treatment coupled with a pyrolysis process. The unique structure enables to expose the active tin oxide and also provides the facile pathways for rapid transfer of electron and electrolyte along with the highly porous carbon foam composed with interconnected carbon nanowires. Therefore, SnO2@NCNW electrocatalyst exhibits good durability and high selectivity for formate formation with a Faradaic efficiency of ca. 90%. This work demonstrates a simple method to rationally design high-dense tin oxide nanocrystals on the conductive carbon support as advanced catalysts for CO2 electroreduction.

Ionic porous polyamide derived N-doped carbon towards highly selective electroreduction of CO_(2)

Electrochemical CO_(2) reduction reaction(CO_(2) RR) has attracted growing attention in energy storage and sustainable production of fuels and chemicals. N-doped carbon materials are preferred metal-free electrocatalysts, but it remains one challenge to finely engineer the active sites and porosity. Herein, we demonstrated that ionic porous polyamides were a kind of versatile precursors to prepare functional carbon materials in a one-step pyrolysis process. The polyamide precursors allowed the maintenance of abundant N species at high temperatures. The existence of ionic moieties and large specific surface area of the precursors promoted the formation of larger porosity carbon with a large specific surface area and sufficient active graphitic-N species by controlling the pyrolysis temperature. The catalyst was highly selective in the CO_(2) RR to produce CO with a maximum Faraday efficiency above 99%, attributable to the improved mass transfer in a large porosity system. This work shows that ionic polyamides are promising carbon precursors for the fabrication of metal-free electrocatalysts for CO_(2) RR.

Facile Preparation and Visible-light Photocatalysis Enhancement of N-Doped β-TiO_2 Nanobelts

A facile preparation of nitrogen-doped β-TiO2（N-doped β-TiO2） nanobelts and their visible-light photocatalytic activity were reported.The preparation of N-doped β-TiO2 nanobelts consisted of cation-exchange between layered sodium titanate nanobelts and NH 4 ＋ in aqueous solution at room temperature and subsequent calcination in air.Such a calcination treatment is beneficial to the formation of monoclinic N-doped β-TiO2 nanobelts.Various measurement results indicate that not only were the nitrogen atoms doped into the lattice of β-TiO2 nanobelts resulting in a strong visible-light absorption,but also a large number of defects were caused by them in the lattice,increasing the stability of β-TiO2.The photocatalysis enhancement of N-doped β-TiO2 nanobelts for the photodegradation of Rhodamine B was demonstrated.

In situ embedded bismuth nanoparticles among highly porous carbon fibers for efficient carbon dioxide reduction

Electrocatalysis provides an optimal approach for the conversion of carbon dioxide(CO_(2))into high-value chemicals,thereby presenting a promising avenue toward achieve carbon neutrality.However,addressing the selectivity and stability challenges of metal catalysts in electrolytic reduction remains a daunting task.In this study,the electrospinning method is employed to fabricate porous carbon nanofibers loaded with bismuth nanoparticles with the help of in situ pyrolysis.The porous carbon nanofibers as conductive support would facilitate the dispersion of bismuth active sites while inhibiting their aggregation and promoting the mass transfer,thus enhancing their electrocatalytic activity and stability.Additionally,nitrogen doping induces electron delocalization in bismuth atoms through metal-support interactions,thus enabling efficient adsorption of intermediates for improving selectivity based on the theoretical calculation.Consequently,Bi@PCNF-500 exhibits the exceptional selectivity and stability across a wide range of potential windows.Notably,its faradaic efficiency(FE)of formate reaches 92.7%in H-cell and94.9%in flow cell,respectively,with good electrocatalytic stability.The in situ characterization and theoretical calculations elucidate the plausible reaction mechanism to obtain basic rules for designing efficient electrocatalyst.

Visible light-induced N-doped TiO_2 nanoparticles for the degradation of microcystin-LR

N-doped nano-crystalline TiO2 powders have been synthesized by the sol-gel method.The shape and crystal structure of the resulting N-doped TiO2 were investigated by X-ray Photoelectron Spectroscopy (XPS),X-ray spectroscopy (XRD),Transmission Electron Microscopy (TEM) and UV-vis reflection spectrum.The results showed that doping TiO2 with nitrogen can lower its band gap and apparently shift its optical response to the visible region.Under the visible light (λ】 420 nm) irradiation,the MC-LR was degraded by the synthesized N-TiO2 nano-material.The variation of MC-LR amount and its intermediates were detected by high performance liquid chromatography (HPLC) and LC-MS,respectively.The mineralization of MC-LR was determined by total organic carbon (TOC) analysis.Simultaneously,transient oxidative species generated during photocatalysis were tracked by electron spin resonance (ESR) and Peroxidase method.All these results indicated that visible-light excited N-TiO2 can activate molecular oxygen and thereby achieve degradation of MC-LR completely within 14 h.The removal of 59% of TOC was achieved after 20 h irradiation.The major oxidative species in the system were hydroxyl radical (·OH) and H2O2.13 Kinds of intermediates were primarily identified in the process.Based on these results,a reasonable conclusion was drawn for the degradation of MC-LR wherein its four positions are easy to be attacked by the photo-generated OH radical followed by the hydrolyzation of peptides.

Co-CoO_x supported onto TiO_(2) coated with carbon as a catalyst for efficient and stable hydrogen generation from ammonia borane

Ammonia borane(AB) can be catalytically hydrolyzed to provide hydrogen at room temperature due to its high potentaial for hydrogen storage. Non-precious metal heterogeneous catalysts have broad application in the field of energy catalysis. In this article, catalysts precursor is obtained from Co-Ti-resorcinol-formaldehyde resin by sol–gel method. Co/TiO_(2)@N-C(CTC) catalyst is prepared by calcining the precursor under high temperature conditions in nitrogen atmosphere. Co-CoO_x/TiO_(2)@N-C(COTC) is generated by the controllable oxidation reaction of CTC. The catalyst can effectively promote the release of hydrogen during the hydrolytic dehydrogenation of AB. High hydrogen generation at a specific rate of 5905 m L min^(-1) g_(Co)^(-1) is achieved at room temperature. The catalyst retains its 85% initial catalytic activity even for its fifth time use in AB hydrolysis. The synergistic effect among Co, Co_(3)O_(4) and TiO_(2) promotes the rate limiting step with dissociation and activation of water molecules by reducing its activation energy. The applied method in this study promotes the development of non-precious metals in catalysis for utilization in clean energy sources.

Thermal and Structural Analyses of PMMA/TiO₂Nanoparticles Composites

In the present work, composites of poly (methyl methacrylate)/titanium oxide nanoparticles (100/0, 97.5/2.5, 95/5, 92.5/7.5, 90/10 and 0/100 wt/wt%)were prepared to be used as bioequivalent materials according to their importance broad practical and medical applications. Thermal properties as well as X-ray diffraction analyses were employed to characterize the structure properties of such composite. The obtained results showed variations in the glass transition temperature (Tg), the melting temperature (Tm), shape and area of thermal peaks which were attributed to the different degrees of crystallinity and the existence of interactions between PMMA and TiO2 nanoparticle molecules. The XRD patterns showed sharpening of peaks at different concentrations of nano-TiO2 powder with PMMA. This indicated changes in the crystallinity/amorphosity ratio, and also suggested that the miscibility between the amorphous components of homo- polymers PMMA and nano-TiO2 powder is possible.The results showed that nano-TiO2 powder mix with PMMA can improve the thermal stability of the homo-polymer under investigation, lead- ing to interesting technological applications.

Construction of MnO2 Nanowire for a High-Performance Lithium Ion Supercapacitor

Developing lithium ion capacitors possessing both brilliant energy and power density is still significant for numerous re-searchers.In this paper,we synthesized MnO2 nanowires via a simple hydrothermal process.The nanostructure MnO2 can expose more electrochemical sites and thus optimize the kinetics of Li+.Moreover,we used MnO2 nanowires(MnO2 NWs)as anode and a N-doped porous carbon(NPC)as cathode to assemble lithium ion capacitors(MnO2 NWs//NPC LIC).Compared to the traditional supercapacitor with aqueous electrolyte,the MnO2 NWs//NPC LIC exhibits a wider voltage of 0-4.2 V,which is helpful to enhance its energy and power density.Furthermore,MnO2 NWs//NPC LIC can deliver an excellent capacity of 150 mAh g-1 with an excellent energy density of 82.7 Wh kg-1 and power density of 1.05 kW kg-1.Meanwhile,a good cyclic stability of LICs with a 20%retention after 1000 times charge and discharge process proves its practical potential,indicating a good promising for the application in storage devices.