Surface Defects Enhanced Visible Light Photocatalytic H₂ Production for Zn‐Cd‐S Solid Solution

Abstract

In order to investigate the defect effect on photocatalytic performance of the visible light photocatalyst, Zn-Cd-S solid solution with surface defects is prepared in the hydrazine hydrate. X-ray photoelectron spectra and photoluminescence results confirm the existence of defects, such as sulfur vacancies, interstitial metal, and Zn and Cd in the low valence state on the top surface of solid solutions. The surface defects can be effectively removed by treating with sulfur vapor. The solid solution with surface defect exhibits a narrower band gap, wider light absorption range, and better photocatalytic perfomance. The optimized solid solution with defects exhibits 571 μmol h(-1) for 50 mg photocatalyst without loading Pt as cocatalyst under visible light irradiation, which is fourfold better than that of sulfur vapor treated samples. The wavelength dependence of photocatalytic activity discloses that the enhancement happens at each wavelength within the whole absorption range. The theoretical calculation shows that the surface defects induce the conduction band minimum and valence band maximum shift downward and upward, respectively. This constructs a type I junction between bulk and surface of solid solution, which promotes the migration of photogenerated charges toward the surface of nanostructure and leads to enhanced photocatalytic activity. Thus a new method to construct highly efficient visible light photocatalysts is opened.

Density-weighted Algorithms for Similarity Computation and Cluster Tree Construction in the RAPD Analysis of Natural Cordyceps sinensis

“…We propose that our findings reflect the dynamic changes in the expression of the multiple intrinsic fungi and fungal genotypes in the different compartments of C. sinensis under the multiple fungi-integrated microecosystem hypothesis [17][18][19]21,[23][24][25][26][27][28]30,33,47], rather than genetic variations under the singlefungus hypothesis [16,29]. Clearly, our interpretation contradicts the hypothesis that the evolutionary distances of O. sinensis are responsible for the differences in the C. sinensis populations in different production areas, which has been proposed by some C. sinensis researchers [38][39]43,45].…”

“…No genotyping information to date has been reported for the different conidiogenous structures or for the different conidia discovered in microcycle conidiation of ascospores/conidia studies. Both the macrocosmic RAPD global profiling and microscopic sequencing and morphological findings challenge the hypothesis that C. sinensis is one species of fungus [16,29], but support the hypothesis that C. sinensis is an integrated microecosystem with multiple intrinsic fungi from over 30 genera [17][18][19][21][22][23][24][25][26][27][28]30,33,47]. More and more mycologists have realized that symbiotic interactions between multiple intrinsic fungi in C. sinensis may be the key to the induction of the C. sinensis sexual fruiting body and formation of ascospores, both naturally and in artificial settings, in strict adherence to Koch's postulates.…”

“…revealed a culture-dependent microbial community or mycobiota in wild C. sinensis with evidence for possible symbiotic interactions among the component fungi [23,37]. In addition to the microcosmic systematics techniques mentioned above, the random amplified polymorphic DNA (RAPD) technique has shown an advantage as a macrocosmic, fuzzy technique (not specific to particular sequences when viewing the study material as a whole) in molecular systematics for comparing overall polymorphism similarities and cluster relationships in different systems, in particular when studying natural C. sinensis with multiple known and unknown, culturable and nonculturable fungi.…”

“…Using microcosmic molecular techniques, such as molecular cloning, rDNA ITS sequencing, MassARRAY SNP mass spectrometry, Southern blotting, DNA conformation analysis and other molecular and biochemical approaches, it has been documented that C. sinensis comprises multiple intrinsic fungi from over 30 genera and at least 6 genotypes of O. sinensis . An anamorph-teleomorph connection has been proposed for Hirsutella sinensis and O. sinensis [16,29]; however, no scientific studies to date have fully satisfied Koch's postulates by detailing the successful artificial induction of the C. sinensis sexual fruiting body and ascospores [23,[29][30][31][32][33][34][35][36]. Based on the microcosmic results of the systematic and molecular systematic studies listed above, researchers have hypothesized that C. sinensis is an integrated micro-ecosystem with differential expressions of multiple intrinsic fungi (representing altered biomass in different compartments of natural C. sinensis during maturation, mainly caused by differential proliferations of intrinsic fungi plus many other biological processes) [18][19][20][21][22][23][24][25][26][27][28]33], and have 1 The Latin name has been used indiscriminately for both the wild product and the teleomorph/holomorph of the C. sinensis fungus.…”

Defect Engineering of Photocatalysts for Solar Energy Conversion

“…OVs confined in WO 3 achieved a high PC evolution rate, which is ascribed to the promotion of light harvesting due to surface plasmon resonance by the introduction of OVs (Figure e) . Surface defects confined in Zn‐Cd‐S solid solution achieved the outstanding PC hydrogen production rate due to the introduction of sulfur defects by the confirmation of X‐ray photoelectron spectra and photoluminescence spectra . Particularly, Zou et al reported metal‐defected TiO 2 and ZnO semiconductors with abundant metal vacancies, presenting a remarkable PC performance and an essential relationship of the defect structure and the PC performance of metal‐defected photocatalysts.…”