On the Formation of Cd–Zn Sulfide Photocatalysts from Insoluble Hydroxide Precursors

Abstract

The formation of Cd-Zn sulfide solid solutions from mixed hydroxides under hydrothermal conditions is investigated in detail. The work specifically aims to understand the formation and the role of nanotwinned mixed sulfide particles that have been reported to show excellent performance in photocatalytic water splitting (Liu, M.; et al. Energy Environ. Sci. 2011, 4, 1372). The influence of additives, pH, autoclave tumbling, and the state of the mixed hydroxide precursor on the mixed sulfides was studied by XRD, XPS, TEM, DR UV-vis, and N2 physisorption. Cd-Zn sulfides are formed via a dissolution-precipitation mechanism. Agitation of the synthetic medium and the formation of soluble intermediate complexes during hydrothermal treatment suppress the formation of a hexagonal wurtzite crystal phase and improve the photocatalytic activity of the mixed sulfides. The role of additives can be understood in terms of complex formation, pH maintenance, and adsorption on the facets of growing crystallites. All Cd-Zn sulfide samples exhibit compositional inhomogeneities, resulting in XRD line broadening and decreased bandgaps as compared with the values predicted by Vegard's law. Detailed TEM analysis revealed that the samples with higher amounts of nanotwinned particles were significantly less active in water reduction. The influence of nanotwinned particles is discussed in terms of extended crystal defects and charge carrier recombination.

Efficient hydrogenation of cinnamaldehyde to 3-phenylpropanol on Ni/NiS-modified twin Zn0.5Cd0.5S under visible light irradiation

“…This structure not only ameliorates shortcomings on the stability of metal sulfides, but also greatly promotes photogenerated charge separation, which promotes the photocatalytic activity remarkably. 15,16 In our previous studies, it was observed that T-Zn x Cd 1−x S exhibits excellent reduction ability of hydrogen protons. The apparent quantum yield (AQY) for photocatalytic H 2 evolution can reach up to 62% at 425 nm without any co-catalysts.…”

Cocatalyst‐Free Reduction of 4,4′‐Dinitrodiphenyl Ether to 4,4′‐Diaminodiphenyl Ether Over Twin‐Crystal ZnxCd1−xS under Visible Light

“…Previous work has reported that the apparent quantum yield (AQY) for photocatalytic H 2 evolution can reach to 62 % at 425 nm without the presence of any co-catalysts. [17] Therefore, we use Zn x Cd 1À x S with nano-twin crystal structure as catalyst for the photocatalytic reduction of DNDPE to ODA in water-ethanol solution under normal pressure, room temperature and visible light irradiation. Without any noble metal cocatalysts or additional hydrogen source, DNDPE shows the conversion of more than 95 % in 10 min and complete conversion within 40 min, which greatly exceeds traditional catalysis method.…”