Cesium doped WO3 (Cs-WO3) photocatalyst with high and stable oxidation activity was successfully synthesized by a one-step hydrothermal method using Cs2CO3 as the doped metal ion source and tungstic ...acid (H2WO4) as the tungsten source. A series of analytical characterization tools and oxygen precipitation activity tests were used to compare the effects of different additions of Cs2CO3 on the crystal structure and microscopic morphologies. The UV–visible diffuse reflectance spectra (DRS) of Cs-doped material exhibited a significant red shift in the absorption edge with new shoulders appearing at 440–520 nm. The formation of an oxygen vacancy was confirmed in Cs-WO3 by the EPR signal, which can effectively regulate the electronic structure of the catalyst surface and contribute to improving the activity of the oxygen evolution reaction (OER). The photocatalytic OER results showed that the Cs-WO3-0.1 exhibited the optimal oxygen precipitation activity, reaching 58.28 µmol at 6 h, which was greater than six times higher than that of WO3-0 (9.76 μmol). It can be attributed to the synergistic effect of the increase in the conduction band position of Cs-WO3-0.1 (0.11 V) and oxygen vacancies compared to WO3-0, which accelerate the electron conduction rate and slow down the rapid compounding of photogenerated electrons–holes, improving the water-catalytic oxygen precipitation activity of WO3.
A highly efficient visible-light-driven photoanode, N2-intercalated tungsten trioxide (WO3) nanorod, has been controllably synthesized by using the dual role of hydrazine (N2H4), which functioned ...simultaneously as a structure directing agent and as a nitrogen source for N2 intercalation. The SEM results indicated that the controllable formation of WO3 nanorod by changing the amount of N2H4. The β values of lattice parameters of the monoclinic phase and the lattice volume changed significantly with the nW: nN2H4 ratio. This is consistent with the addition of N2H4 dependence of the N content, clarifying the intercalation of N2 in the WO3 lattice. The UV-visible diffuse reflectance spectra (DRS) of N2-intercalated exhibited a significant redshift in the absorption edge with new shoulders appearing at 470–600 nm, which became more intense as the nW:nN2H4 ratio increased from 1:1.2 and then decreased up to 1:5 through the maximum at 1:2.5. This addition of N2H4 dependence is consistent with the case of the N contents. This suggests that N2 intercalating into the WO3 lattice is responsible for the considerable red shift in the absorption edge, with a new shoulder appearing at 470−600 nm owing to formation of an intra-bandgap above the VB edges and a dopant energy level below the CB of WO3. The N2 intercalated WO3 photoanode generated a photoanodic current under visible light irradiation below 530 nm due to the photoelectrochemical (PEC) water oxidation, compared with pure WO3 doing so below 470 nm. The high incident photon-to-current conversion efficiency (IPCE) of the WO3-2.5 photoanode is due to efficient electron transport through the WO3 nanorod film.
To explore high-performing alternatives to platinum-based catalysts is highly desirable for lowering costs and thus promoting fuel cell commercialization. Herein, self-supported Fe-N-C materials were ...prepared by the pyrolysis of dual precursors including EDTA ferric sodium (EDTAFeNa) and melamine (MA), followed by acid-leaching and final annealing. Towards an oxygen reduction reaction (ORR) in 0.1 M KOH, the as-prepared MA/EDTAFeNa-HT2 delivered onset (Eonset) and half-wave (E1/2) potentials of 0.97 and 0.84 V vs. RHE, respectively, identical with that of a state-of-the-art Pt/C catalyst, accompanied with predominantly a four-electron pathway. The introduction of MA and extension of acid-leaching promoted a positive shift of 50 mV for E1/2 relative to that of only the EDTAFeNa-derived counterpart. It was revealed that the enhancement of ORR activity is attributed to a decrease in magnetic Fe species and increase in pyridinic/quanternary nitrogen content whilst nearly excluding effects of the graphitization degree, variety of crystalline iron species, and mesoscopic structure. The usage of dual precursors exhibited great potential for the large-scale production of inexpensive and efficient Fe-N-C materials.
High-entropy nitride powders are one of prerequisite materials for the preparation of high-performance high-entropy nitride ceramics. In this paper, high-entropy (HfZrTiNbTa)N powders were ...synthesized via nitride (i.e., silicon nitride (Si3N4)) thermal reduction with soft mechano-chemical assistance. The results show that metal oxides like hafnium dioxide (HfO2), zirconium dioxide (ZrO2), titanium dioxide (TiO2), niobium pentoxide (Nb2O5), and tantalum pentoxide (Ta2O5) can all be transformed into the corresponding metal nitrides in the presence of Si3N4 at 1700 ℃, and solid solution of the metal nitrides can be formed as the temperature increases to 2100 ℃. The high-entropy (HfZrTiNbTa)N powders with submicron-sized particles, a narrower size distribution, and a single face-centered cubic (fcc) structure are obtained from raw material mixtures ground for 10 h and subsequently sintered at 1800 ℃. In addition, the high-entropy bulk nitride ceramics with relative density (Rw) of 94.31%±0.76%, Vickers hardness of 21.00±0.94 GPa, and fracture toughness (KIC) of 3.18±0.16 MPa·m1/2 are obtained with submicron-sized powders, which are superior to those obtained with micron-sized powders.
In this work, a highly efficient wide-visible-light-driven photoanode, namely, nitrogen and sulfur co-doped tungsten trioxide (S-N-WO3), was synthesized using tungstic acid (H2WO4) as W source and ...ammonium sulfide ((NH4)2S), which functioned simultaneously as a sulfur source and as a nitrogen source for the co-doping of nitrogen and sulfur. The EDS and XPS results indicated that the controllable formation of either N-doped WO3 (N-WO3) or S-N-WO3 by changing the nW:n(NH4)2S ratio below or above 1:5. Both N and S contents increased when increasing the nW:n(NH4)2S ratio from 1:0 to 1:15 and thereafter decreased up to 1:25. The UV-visible diffuse reflectance spectra (DRS) of S-N-WO3 exhibited a significant redshift of the absorption edge with new shoulders appearing at 470–650 nm, which became more intense as the nW:n(NH4)2S ratio increased from 1:5 and then decreased up to 1:25, with the maximum at 1:15. The values of nW:n(NH4)2S ratio dependence is consistent with the cases of the S and N contents. This suggests that S and N co-doped into the WO3 lattice are responsible for the considerable redshift in the absorption edge, with a new shoulder appearing at 470–650 nm owing to the intrabandgap formation above the valence band (VB) edge and a dopant energy level below the conduction band (CB) of WO3. Therefore, benefiting from the S and N co-doping, the S-N-WO3 photoanode generated a photoanodic current under visible light irradiation below 580 nm due to the photoelectrochemical (PEC) water oxidation, compared with pure WO3 doing so below 470 nm.
The rising tension in the South China Sea since 2009 almost overturns the sound political and economic relations established between China and the ASEAN states since 1997. Better handling of the ...issue to ease the tension of territorial disputes in the South China Sea is thus the key to goodneighbourliness among China and ASEAN's claiming states. The ASEANChina Declaration of the Conduct of Parties (DOC) signed by China and the ASEAN countries in 2002 has not reached its purpose of promoting a peaceful, friendly and harmonious environment in the South China Sea. Instead, the past decade has witnessed numerous clashes between the sovereignty-claimants. Hence, the South China Sea has actually become a potential "battlefield" if consultations or negotiations among the parties concerned have not been effectively or well handled. This paper describes the current overlapping sovereignty claims of related parties around the South China Sea, introduces the mainstream opinions in mainland China toward this critical sovereignty issue, and discusses the evolving academic viewpoints of the Chinese scholars on the South China Sea's territorial disputes, and attempts to seek an alternative approach to handle these complicated sovereignty disputes and raises some proposals for this purpose. PUBLICATION ABSTRACT
SrTiO3 nanoparticle (NP) photocatalyst was synthesized with a facile and environmentalfriendly hydrothermal method using tetrabutyltitanate, strontium oxide, and ethanolamine as precursors at low ...temperature without alkali as mineralizer for the first time. The SrTiO
3
nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and N
2
Brunauer–Emmett–Teller (BET) method. The SrTiO
3
catalyst synthesized at 120 °C (STO-120) exhibited the highest photocurrent intensity among the samples synthesized at different hydrothermal temperatures. The high photocatalytic performance of STO-120 was mainly attributed to the more homogeneous and minimum nanoparticle size, the highest surface area, and the maximum light absorption property among the four different samples. This work presented an applicable and facile method to fabricate a highly active and stable SrTiO
3
photocatalyst for organic pollutant degradation.
Zirconium nitride (ZrN) ceramics were prepared via hot pressed sintering (HP) at 1750 °C in N
2
atmosphere with ZrO
2
–Y
2
O
3
as sintering additive. X-ray diffraction was applied to analyze the ...phase composition of the as-prepared ceramics to study the high temperature phase relation in ZrN–ZrO
2
–Y
2
O
3
ternary system and establish ZrN–ZrO
2
–Y
2
O
3
ternary phase diagrams. The results show that ZrN and tetragonal ZrO
2
(t-ZrO
2
) solid solution, face-centered cubic ZrO
2
(c-ZrO
2
) solid solution, body-centered cubic Y
2
O
3
(c-Y
2
O
3
) solid solution coexist in the system of ZrN–ZrO
2
–Y
2
O
3
.
Nitrogen-doped mesoporous carbon/poly-o-phenylenediamine composites (denoted as N-MC/PoPD) were successfully synthesized by sacrificial hard template method followed by in situ oxidation ...polymerization initiated by FeCl3. It is revealed that the resultant N-MC/PoPD composites still remained original graphitization structure and narrow pore size distributions (centered at ∼3.8 nm) but suffered visibly monotonical decrease in specific surface area after oPD was increasingly polymerized onto N-MC with an increase of the mass ratio of PoPD to N-MC from 1:1 to 5:1. As supercapacitor electrode measured by galvanostatic charge-discharge in 6 mol L−1 KOH, a volcano curve was found when plotting specific capacitance of the N-MC/PoPD versus the mass ratio of N-MC to oPD; the N-MC/PoPD(2:1) with moderate surface area and the highest electrochemical conductivity delivered the highest specific capacitance of 229 F g−1 at a current density of 1 A g−1, which is twice of that obtained on the single N-MC with the maximum surface area. The remarkable enhancement in specific capacitance could be ascribed to the synergistic effect between two components of N-MC and PoPD.
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