ABSTRACT
Simultaneously improving the activity and stability of catalysts for anodic oxygen evolution reaction (OER) in proton exchange membrane water electrolysis (PEMWE) remains a notable challenge. Here, we report a chromium-doped ruthenium dioxide with oxygen vacancies, termed Cr0.2Ru0.8O2-x, that drives OER with an overpotential of 170 mV at 10 mA cm-2 and operates stably over 2000 h in acidic media. Experimental and theoretical studies show that the synergy of Cr dopant and oxygen vacancy induces an unconventional dopant-mediated hydroxyl spillover mechanism. Such dynamic hydroxyl spillover from Cr dopant to Ru active site changes the rate-determining step from OOH* formation to O2 formation and thus greatly improves the OER performance. Moreover, the Cr dopant and oxygen vacancy also play a crucial role in stabilizing surface Ru and lattice oxygen in the Ru-O-Cr structural motif. When assembled into the anode of a practical PEMWE device, Cr0.2Ru0.8O2-x enables long-term durability of over 200 h at an ampere-level current density and 60 degrees centigrade.
ABSTRACT
The incorporated Zn(0.5)Cd(0.5)S (ZCS) nanorods with MoS2/RGO cocatalysts by a simultaneous reduction reaction was reported. The preparation of RGO and formation of MoS2 with intimate interfacial contact with ZCS were achieved. Through the optimizing of each component proportion, the ZCS@MoS2/RGO hybrid with 1.5 wt % MoS2 and 3 wt % RGO showed the highest photocatalytic H2 production activity (2.31 mmol/h) with long time stability (50 h). The relative mechanism has been investigated. It is believed that the stabilizing and improving solar H2 generation is originating from dual charge transfer pathway from excited ZCS to RGO, then to MoS2 due to intimate interfacial structure.
ABSTRACT
Different phases and morphologies of molybdate hydrates MMoO 4. nH 2O (M = Co, Ni, Mn, n = 0, 3/4, 1) nano/microcrystals, which include NiMoO 4.H 2O microflowers, MnMoO 4.H 2O microparallelogram plates, and CoMoO 4.3/4H 2O microrods, can be selectively synthesized by a hydrothermal process. The pH and reaction temperature have a crucial influence on the synthesis and shape evolution of the final products. Uniform CoMoO 4.3/4H 2O and NiMoO 4.H 2O nanorod bundles can be produced by a hydrothermal process with the assistance of PEG-400. The calcination of CoMoO 4.3/4H 2O and NiMoO 4.H 2O at 500 and 550 degrees C, respectively, allows the formation of monoclinic beta-CoMoO 4 and alpha-NiMoO 4. The antiferromagnetic property of MnMoO 4.H 2O, MnMoO 4, and CoMoO 4.3/4H 2O has been studied for the first time. The photocatalytic activity of metal molybdate particles with different morphologies has been tested by degradation of acid fuchsine under visible light. Electrochemical performances of MMoO 4 (M = Ni, Co) nanorod bundles and MnMoO 4 microrods have been evaluated.
ABSTRACT
Silica@carbon core-shell spheres have been synthesized via a hydrothermal carbonization procedure with glucose as the carbon precursor and silica spheres as the cores. Such SiO(2)@C core-shell spheres can be further used as templates to produce SiO(2)@C@SiO(2), and SiO(2)@SiO(2) spheres with a vacant region in two SiO(2) shells, noble-metal nanoparticle loaded SiO(2)@C core-shell spheres, and hollow carbon capsules through different follow-up processes. The obtained core-shell materials possess remarkable chemical reactivity in reducing noble-metal ions to nanoparticles, e.g., platinum. These unique core-shell spherical composites could find applications in catalyst supports, adsorbents, encapsulation, nanoreactors, and reaction templates.