Photocatalytic nonoxidative coupling of methane to ethylene over carbon-doped ZnO/Au catalysts

A photocatalytic nonoxidative coupling of methane to multi-carbon compounds remains a huge challenge due to its high dissociation energy of C–H bonds and sluggish charge carrier dynamics.Au-modified carbon-doped ZnO(C-ZnO/Au)photocatalyst is constructed by an interfacial modification-assisted self-assembly approach for efficient photocatalytic nonoxidative coupling of methane to ethylene and hydrogen(2CH_4=C_2H_4+2H_2).Benefitting from the presence of C-ZnO/Au interfaces,the catalyst not only weakens the excitonic confinement to improve the photogenerated charge carrier separation,but also enhances the stability of lattice oxygen to suppress C_2H_4 overoxidation.Moreover,this hybrid catalyst also accelerates the generation of Zn~+–O~–pairs to activate C–H bonds,stabilizes the important reaction intermediate(*OCH_3)to achieve the C–C coupling,and promotes the generation of low-valence Zn to accelerate the dehydrogenation of the*OC_2H_5 into C_2H_4.Therefore,a stable photocatalytic methane conversion performance can be achieved over C-ZnO/Au heterojunctions with a stoichiometric generation of the oxidation product(C_2H_4,45.85μmol g~(-1)h~(-1))and reduction product(H_2,88.07μmol g~(-1)h~(-1)).This work provides deep insights into the elemental doping and oxide/Au interfaces for the enhanced photocatalytic activity and product selectivity under mild conditions in the absence of extra oxidants.

Structure and composition study of carbon-doped titanium oxide film combined with first principles

Carbon-doped titanium oxide(C/Ti-O)films were prepared on Si(100)wafer,stainless steel(type 304)and glass by reactive magnetron sputtering(RMS)using CO2 gas as carbon and oxygen source under room temperature(RT).X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)were used to analyze structure and composition of the as-prepared C/Ti-O film.It could be observed from XRD that the as-prepared C/Ti-O film contained TiO crystal phase structure.Ti2p XPS spectrum of the as-prepared C/Ti-O film showed that the valences of titanium were made up of Ti^(2+),Ti^(3+)and Ti^(4+).C1s XPS spectrum revealed that carbon was doped into titanium oxide based on the existence of the typical Ti-C bond.The optical absorption curve by ultraviolet-visible(UV-Vis)spectrophotometer showed that the C/Ti-O film appeared the remarkable red shift of absorption edge,which contributed to C substitution in O sites in amorphous TiO_(2).Photocatalysis test using methyl orange(MO)as indicator confirmed that the as-prepared C/Ti-O film had photocatalytic activity.Combined with the results of the tests and first-principles calculations,a potential photocatalysis mechanism was proposed.

Carbon-doped surface unsaturated sulfur enriched CoS2@rGO aerogel pseudocapacitive anode and biomass-derived porous carbon cathode for advanced lithium-ion capacitors

As a hybrid energy storage device of lithium-ion batteries and supercapacitors,lithium-ion capacitors have the potential to meet the demanding needs of energy storage equipment with both high power and energy density.In this work,to solve the obstacle to the application of lithium-ion capacitors,that is,the balancing problem of the electrodes kinetic and capacity,two electrodes are designed and adequately matched.For the anode,we introduced in situ carbon-doped and surface-enriched unsaturated sulfur into the graphene conductive network to prepare transition metal sulfides,which enhances the performance with a faster lithium-ion diffusion and dominant pseudocapacitive energy storage.Therefore,the lithium-ion capacitors anode material delivers a remarkable capacity of 810 mAh·g^(−1) after 500 cycles at 1 A·g^(−1).On the other hand,the biomass-derived porous carbon as the cathode also displays a superior capacity of 114.2 mAh·g^(−1) at 0.1 A·g^(−1).Benefitting from the appropriate balance of kinetic and capacity between two electrodes,the lithium-ion capacitors exhibits superior electrochemical performance.The assembled lithium-ion capacitors demonstrate a high energy density of 132.9 Wh·kg^(−1) at the power density of 265 W·kg^(−1),and 50.0 Wh·kg^(−1) even at 26.5 kW·kg^(−1).After 10000 cycles at 1 A·g^(−1),lithium-ion capacitors still demonstrate the high energy density retention of 81.5%.

Multifunctional interstitial-carbon-doped FeCoNiCu high entropy alloys with excellent electromagnetic-wave absorption performance

Electromagnetic-wave absorbing(EMA)materials that have efficient absorption performances,great me-chanical properties and chemical stability are rare and yet essential for communication security and pro-tection.Herein,flaky interstitial-carbon-doped FeCoNiCu high entropy alloys(HEAs)as novel EMA ma-terials were successfully prepared by high-energy ball-milling method.Interstitial-carbon doping as a modulating approach impacted the phase forming,morphology and electromagnetic properties of Fe-CoNiCu HEAs.Impedance matching was significantly optimized via tuning interstitial carbon contents.The carbon-doped FeCoNiCu HEAs with appropriate carbon contents delivered superior EMA performance compared with other HEAs EMA materials.Strong reflection loss as low as-61.1 dB in the Ku band,broad effective absorption bandwidth of 5.1 GHz was achieved for FeCoNiCuC_(0.04).Moreover,the carbon-doped FeCoNiCu HEAs exhibited excellent mechanical hardness and chemical stability.This work not only suggests that interstitial-carbon doping is an available approach to tuning electromagnetic properties of HEAs,but also presents carbon-doped FeCoNiCu HEAs as promising EMA materials for civilian and mili-tary due to the efficient absorption,broad bandwidth,great durability and stability.

A first-principles study of reaction mechanism over carbon decorated oxygen-deficient TiO_(2) supported Pd catalyst in direct synthesis of H_(2)O_(2)

The choice of support is one of the most significant components in the direct synthesis of H_(2)O_(2).Aiming to improvement of activity and selectivity of H_(2)O_(2) on Pd/TiO_(2) surface,we systematically investigated the important elementary steps on Pd/TiO_(2)-Vo@C,Pd/TiO_(2)-Vo,Pd/TiO_(2)-2 Vo,Pd/TiO_(2),and Pd/C using the first-principles calculations.The Bader charge analysis and charge density difference of O_(2) adsorption elucidate the relationship between the electronic distribution and chemisorption energy.The effective barrier analysis further enables to quantitatively estimate the reactivity of H_(2)O_(2) and H2O.We demonstrate unambiguously that the selectivity of H2O formation is boosted as the oxygen vacancy concentration raised.Moreover,the introduction of C into a TiO_(2) with appropriate oxygen vacancies can slightly reduce the effective barrier for H_(2)O_(2) formation and increase the effective barrier for H2O formation leading to a higher activity and selectivity of H_(2)O_(2) formation.Our finding suggests that carbon-doped oxygen vacancy TiO_(2) supported Pd is potential alternative catalyst compared with the Pd/TiO_(2).

Boron nitride for enhanced oxidative dehydrogenation of ethylbenzene

It is demonstrated experimentally and confirmed theoretically that highly defective boron nitride showed outstanding performance for oxidative dehydrogenation of ethylbenzene.The catalyst is derived from carbon-doped hexagonal boron nitride nanosheets synthesized via a two-step reaction when participating the oxidative dehydrogenation reaction.The first step yields a polymeric precursor with the atomic positions of B,C,N relatively constrained,which is conducive for the formation of carbon atomic clusters uniformly dispersed throughout the BN framework.During the oxidative dehydrogenation of ethylbenzene to styrene,the nanoscale carbon clusters are removed and highly defective boron nitride(D-BN)is obtained,exposing boron-rich zigzag edges of BN that act as the catalytic sites.The catalytic performance of D-BN is therefore remarkably better than un-doped h-BN.Our results indicate that dispersed C-doping in h-BN is highly effective in terms of defect formation and resultant enhanced activity in oxidative dehydrogenation reactions.

Photocatalytic Activity of Anodized Titanium Sheets under Ultra-Violet and Visible Light Irradiation

A commercially pure titanium sheet precipitated TiC in the surface layer was fabricated by anodic oxidation in NH4NO3 solution and heat treatment in air. The fabricated sheet showed relatively high photocatalytic activity in 0.1 M KI solution, which was close to the activity level of the P-25 particle made by Degussa Corporation. It exhibited photocatalytic activity in antifungal and antivirus tests under black light irradiation. The better photocatalytic activity under black light irradiation is considered to be related to the formation of anatase and rutile type titanium dioxides and rough surface. It also showed photocatalytic activity under visible light irradiation, which is considered to be attributable to carbon and nitrogen doping in titanium dioxide.