•The preferential adsorption of CO2 over CH4 improves with coal rank.•Pore structure of coal affects the thermodynamics of adsorption of CO2 and CH4.•Adsorbed CO2 has a more ordered configuration ...than CH4 on different rank coals.
In this paper, the pore structures of three different rank coals sampled from China (anthracite, bituminous coal and lignite) were characterized by CO2 and N2 adsorption. The isothermal adsorption curves of CO2 and CH4 on three samples were measured by gravimetric method and fitted by Langmuir model. The preferential selectivity (αCO2/CH4) was calculated using the Langmuir parameters of CO2 and CH4, and the Henry’s coefficient (KH) was obtained with the help of virial equation. More importantly, a comparative analysis of adsorption thermodynamics of CO2 and CH4 on three different rank coals, including surface potential (Ω), Gibbs free energy change (ΔG) and entropy loss (ΔS), was presented according to the adsorption data. It is found that the uptakes of CO2 and CH4 on anthracite are the largest, followed by lignite and bituminous coal in sequence. αCO2/CH4 increases with the increase of coal rank. Low temperature helps injected CO2 to displace pre-adsorbed CH4. The KH values on anthracite are the biggest, while KH values on bituminous coal are the smallest. Ω, ΔG and ΔS of CO2 and CH4 all exhibit a U-shaped function with maturity. Anthracite has the highest Ω, ΔG and ΔS, while bituminous coal has the lowest Ω, ΔG and ΔS. The thermodynamics parameters of Ω, ΔG and ΔS are affected by pore size distributions of three coals. Ω, ΔG and ΔS of CH4 are smaller than those of CO2. CO2 adsorption on coal is more favorable and spontaneous, and adsorbed CO2 molecules form a more efficient packing on coal.
We successfully fabricate a new type of composite photocatalyst through modifying CdS nanorods using a noble-metal-free co-catalyst NC@Mo2N (molybdenum nitride deposited nitrogen-doped carbon ...matrix). The obtained CdS/NC@Mo2N composites show greatly enhanced photocatalytic hydrogen generation abilities. Among all studied samples, CdS/5% NC@Mo2N exhibited the optimal photocatalytic activity, owning a H2-production rate of 7294 μmol h−1 g−1 and showing an apparent quantum yield of 13.7%, which are almost five times higher than for the pure CdS. Moreover, through introducing the co-catalyst NC@Mo2N, the composites become more stable under a long term photocatalytic reaction as compared to pure CdS. The improved photocatalytic capability of the CdS/NC@Mo2N is mainly ascribed to the following two reasons: (1) Mo2N supplies abundant active sites for the water-spitting reaction and lowers the overpotential. (2) The nitrogen-doped carbon matrix promotes charge transfer and greatly enhances the conductivity of the composites.
A new-type composite photocatalyst, CdS nanorods modifyed by a noble-metal-free co-catalyst NC@Mo2N (molybdenum nitrides deposited nitrogen-doped carbon matrix), was prepared for the first time. The synthesized composites showed much enhanced hydrogen evolution activity compared to pure CdS. Display omitted
•CdS nanorods were modified with NC@Mo2N.•The synergistic effect between NC and Mo2N plays an important role in improving the hydrogen evolution.•The synthetized composites showed much enhanced hydrogen evolution activity.
SUMMARY
Crustal anisotropy parameters beneath the Qinling Orogenic Belt (QOB) and its surrounding areas (including the northeastern Tibetan Plateau) are investigated by harmonic fitting the arrival ...times of the P-to-S converted phase from the Moho and an intracrustal discontinuity. The measurements reveal strong and spatially varying crustal anisotropy beneath the study region, with an average splitting time of 0.50 ± 0.17 s. The eastern Kunlun Orogen (EKLO), western part of QOB (WWQL) and Longmenshan block (LMB) present relatively larger crustal anisotropy, and the fast orientations changed gradually from NWW–SEE in EKLO and WWQL to NEE–SWW in LMB. The crustal anisotropy measurements, combined with the results from ambient-noise tomography and gravity inversion, suggest that the middle-lower crustal flow induced by the inhomogeneous crustal thickening during the early stage of plateau growth exists beneath these areas. The fast orientations beneath the eastern part of the QOB are predominantly NNE–SSW, nearly orthogonal to that from local shear wave splitting and teleseismic XKS splitting. The crustal anisotropy measurements suggest a layered deformation beneath the eastern QOB. The upper crust retains the fossil deformation formed during the main orogeny, the middle-to-lower crust is dominated by the N–S oriented subduction, collision and continued convergence between the North China Block, South China Block and Qinling microblocks; the upper mantle is decoupled from the crust and mainly controlled by the mantle flow from the Tibetan Plateau.
Photocatalytic hydrogen evolution is a promising technology in solving the global energy and environment issues. Therefore, it is urgent to develop highly efficient, nonprecious metal and stable ...photocatalysts. In this work, we synthesized a highly efficient Ni2P-CdS/g-C3N4 composite based on the concept of combining heterojunction engineering with co-catalyst modification. When employed as a photocatalyst for water splitting, the obtained best composite (5% Ni2P-CdS/g-C3N4) displayed dramatically enhanced hydrogen evolution activity at the rate of 44 450 μmol h-1 g-1, which was about 27 times higher than that of pure CdS (1668 μmol h-1 g-1). The apparent quantum yield at 420 nm reaches 46.3%. The excellent photocatalytic activity and stability can be ascribed to the synergistic effect of the intimate contact between CdS and g-C3N4 and the surface co-catalyst modification. Specifically, the g-C3N4 coated on the CdS nanorods can effectively promote the electron-hole pair separation spatially and Ni2P can lower the overpotential of H+ reduction.
•The crustal thickness and Poisson’s ratio models are proposed from H–k stacking.•The basement of Simao block belongs to the Gangwana plate.•A 3D shear-wave velocity structure model is constructed ...though joint inversion.•A migration model is proposed for middle-to-lower crustal materials in the study region.
Researches on the southeastern Tibetan Plateau provide important insights into the tectonic evolution of the Tibetan Plateau. In this study, we have constructed a high-resolution 3D shear-wave velocity model through joint inversion of receiver functions and surface wave dispersion data. The crustal thickness and Poisson’s ratio models are first determined by H–k stacking of receiver functions. The crustal thickness changes from 30km in the south to 62km in the north, presenting strong lateral variations. The fundamental mode of Rayleigh wave dispersion data spanning periods from 8 to 65s were then jointly used to constraint the absolute shear-wave velocity. The shear-wave velocity structure shows lateral variations. There are low velocity zones distributed in the crust and upper mantle. Two continuously distributed low velocity zones are clearly presented in the middle-to-lower crust, which extend from north toward southeast and southwest, respectively, joining together in southern Yunnan. In this study, we deduced the migration model of soft materials in middle-to-lower crust in southeastern Tibetan Plateau, which explains that the resistance from Sichuan Basin separates the flowing materials from Tibetan Plateau into southeast and northwest branches. They flow along the west margin of Sichuan Basin and then extrude out from northeastern and southeastern Tibetan Plateau respectively. The southeast branch is blocked and cannot flow in the entire crust. It is limited in a certain range of depths and channels. The two low velocity zones in this study possibly present two flow channels of the middle-to-lower crustal materials extruded from the Tibetan Plateau.
•Lithospheric model in the central and northeastern Tibetan is proposed by joint inversion.•Widely spread mid-crustal partial melts are observed in the central and northeastern Tibetan.•Crustal ...channel flow model may contribute largely to the Tibetan deformation.
A crustal and uppermost mantle shear-wave velocity model beneath the central and northeastern Tibetan Plateau is obtained from the joint analysis of Rayleigh wave phase dispersions and teleseismic P-wave receiver functions at 188 broadband seismic stations deployed in this region. This newly presented model reveals wide-spread low velocity zones in the middle crust, and these zones are mainly confined to the region south of the Kunlun Fault. The velocities in the low velocity zones are extremely low (<∼3.3 km/s), suggesting the presence of actively melting or previously melted materials in the crust, and further implying the possibly large contributions of the crustal channel flow model to the deformation in the Tibetan Plateau. Additionally, a continuous low velocity anomaly in the uppermost mantle beneath the eastern Kunlun Fault, the Songpan-Ganzi terrane and part of the Qiangtang terrane is observed, which may suggest an induced local mantle upwelling in this region.
PDF
