Zinc orthogermanate was prepared via a hydrothermal method and a remarkable synergistic effect on the photocatalytic activity for overall water splitting was found for Zn 2 GeO 4 co-loaded with noble metals (Pt, Rh, Pd, Au) and metal oxides (RuO 2 , IrO 2 ). The photocatalytic activity of Pt-RuO 2 /Zn 2 GeO 4 for overall water splitting is 2.2 times of Pt/Zn 2 GeO 4 and 3.3 times of RuO 2 /Zn 2 GeO 4 . Photocatalytic half reactions evaluation of water splitting for H 2 and O 2 productions shows that Pt plays the major roles in H 2 production and RuO 2 promotes the O 2 production. The roles and valence states of co-catalysts and the mechanism of photocatalytic reaction are discussed.
Co-catalysts are a major factor to enhance photocatalytic H2 activity; they are mainly composed of expensive noble metals. Here, we reported a new non-noble-metal co-catalyst Mo2 C that efficiently improves the photocatalytic H2 evolution of CdS under visible light irradiation. Mo2 C is prepared by temperature-programmed reaction with molybdenum oxide as precursor, and the Mo2 C/CdS composite is prepared by deposition of CdS on Mo2 C. The optimum composite 2.0 % Mo2 C/CdS shows a high H2 evolution rate of 161 μmol h(-1) , which is ten times higher than that of CdS alone and 2.3 times higher than the optimum for 1.0 % Pt/CdS. Moreover, the Mo2 C/CdS is stable for 50 h. This study presents a new low-cost non-noble-metal co-catalyst as a photocatalyst to achieve highly efficient H2 evolution.
A three-component photocatalyst IrO
x
−ZnO/Zn2−x
GeO4−x−3y
N2y
was designed and investigated for photocatalytic O2 production under visible light irradiation. It was found that loading of IrO
x
or ZnO alone could efficiently improve the photocatalytic activity. The even higher photocatalytic activity was achieved by coloading of IrO
x
and ZnO on Zn2−x
GeO4−x−3y
N2y
, which was about 5.6 times that of Zn2−x
GeO4−x−3y
N2y
alone. The photocatalysts simultaneously coloaded with IrO
x
and ZnO on Zn2−x
GeO4−x−3y
N2y
showed higher photocatalytic activities than those coloaded with IrO
x
and ZnO sequentially. The high resolution transmission electron microscopy (HRTEM) characterization showed that a solid solution phase junction (SSPJ) was possibly formed at the interface of ZnO and Zn2−x
GeO4−x−3y
N2y
nanaoparticles. This phase junction formed between ZnO and Zn2−x
GeO4−x−3y
N2y
may promote the charge separation and consequently result in the enhanced photocatalytic activity.
Earth-abundant catalysts (cocatalysts) for photocatalysis, photoelectrocatalysis, and electrocatalysis have attracted increased attention due to the potentially reduced cost for large-scale application. Here, we first report and demonstrate that improving the capacitance of cocatalysts of Mo 2 N by modifying the morphology and orientations could produce a better photocatalytic hydrogen evolution reaction (HER) activity on CdS. Among rod, sheet, and sphere shapes of Mo 2 N, the (111)-orientated rod h-Mo 2 N was found to be the most efficient. The hydrogen evolution activity of h-Mo 2 N/CdS is 6.1 times that of the Pt/CdS and 30.1 times that of the bare CdS. A controlling experiment showed that the superior photocatalytic HER activity can be attributed to the higher capacitance of h-Mo 2 N. This study opens up a pathway to develop novel cocatalysts for photocatalyst by adjusting the capacitance through morphology controls.
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