Engineering Charge Transfer Characteristics in Hierarchical Cu2S QDs @ ZnO Nanoneedles with p–n Heterojunctions: Towards Highly Efficient and Recyclable Photocatalysts

Abstract

Equipped with staggered gap p-n heterojunctions, a new paradigm of photocatalysts based on hierarchically structured nano-match-shaped heterojunctions (NMSHs) Cu2S quantum dots (QDs)@ZnO nanoneedles (NNs) are successfully developed via engineering the successive ionic layer adsorption and reaction (SILAR). Under UV and visible light illumination, the photocatalytic characteristics of Cu2S@ZnO heterojunctions with different loading amounts of Cu2S QDs are evaluated by the corresponding photocatalytic degradation of rhodamine B (RhB) aqueous solution. The results elaborate that the optimized samples (S3 serial specimens with six cycles of SILAR reaction) by means of tailored the band diagram exhibit appreciable improvement of photocatalytic activities among all synthesized samples, attributing to the sensitization of a proper amount of Cu2S QDs. Such developed architecture not only could form p–n junctions with ZnO nanoneedles to facilitate the separation of photo-generated carries but also interact with the surface defects of ZnO NNs to reduce the electron and hole recombination probability. Moreover, the existence of Cu2S QDs could also extend the light absorption to improve the utilization rate of sunlight. Importantly, under UV light S3 samples demonstrate the remarkably enhanced RhB degradation efficiency, which is clearly testified upon the charge transfer mechanism discussions and evaluations in the present work. Further supplementary investigations illustrate that the developed nanoscale Cu2S@ZnO heterostructures also possess an excellent photo-stability during our extensive recycling photocatalytic experiments, promising for a wide range of highly efficient and sustainably recyclable photocatalysts applications.

Assessing the Applicability of Photocatalytic-Concrete Blocks in Reducing the Concentration of Ambient NO2 of Chandigarh, India, Using Box–Behnken Response Surface Design Technique: A Holistic Sustainable Development Approach

“…Figure 1 plots the network of keywords for the last eight years developed using Scopus database. e study indicates strong network relationship between photocatalysis, titanium dioxide, and nitrogen oxides which has also been found in literature review [16,17]. Recently, titanium dioxide nanoparticles, zinc oxide, and oxide minerals are used for manufacturing of concrete blocks.…”

“…On the other hand, applications of photocatalysis have already been studied vastly in oxidation of pollutants in different environmental media, such as air, water, and soil [14,15]. Among the various oxidation agents, such as TiO 2 , ZnO, Ag 3 PO 4 , CuO, AgI, and Cu 2 S, TiO 2based photocatalysis was reported to be most advantageous because of its high efficiency, easier mobilization on different substrates, lower operational cost, and no damage to environment and living beings [16,17]. erefore, in recent years, scientific community is also working towards exploring the applicability of photocatalysis in reduction of urban-air pollution [18][19][20].…”

Controlled Growth of LDH Films with Enhanced Photocatalytic Activity in a Mixed Wastewater Treatment

“…However, in one study, the diffusion of K + ions from poly(heptazine imide) (PHIK) to a metal–organic framework (MOF) made PHIK more negatively charged and MOF more positively charged, which provided the strongest interaction between PHIK and MOF and resulted in superior photocatalytic activity through rhodamine B degradation [18]. It has also been shown that the formation of heterojunctions could increase photocatalytic properties, such as Cu 2 S/ZnO, Cu 2 O/TiO 2 , and CuInS 2 /TiO 2 [19,20,21], and that the presence of Na 2 S hole scavengers increased the photoreduction of CO 2 to form (HCOO − ) on ZnS [22]. Finally, due to the different Fermi levels between heavy metals and LDHs, heavy metals deposited on the surface of LDHs could act as electron traps to prevent electron-hole recombination [5,9,10], which would improve the photocatalytic performance of LDHs.…”

Two Hybrid Au-ZnO Heterostructures with Different Hierarchical Structures: Towards Highly Efficient Photocatalysts

“…Sunlight-driven semiconductor-based heterogeneous photocatalysts have been extensively investigated due to their straightforward operation, environmental friendliness and high efficiency 1–3 . Thus, different semiconductors have been explored to improve their cost-efficiency, long-term stability and efficiency 4–6 .…”

“…Thus, different semiconductors have been explored to improve their cost-efficiency, long-term stability and efficiency 4–6 . Among these, ZnO stands out due to its excellent characteristics, e.g., a direct wide band gap (Eg = 3.37 eV), good availability, cost effectiveness, low-toxicity, unique acoustic and optoelectronic properties, chemical stability and nanoscale tunability 7–12 . Nevertheless, the wide bandgap energy of ZnO allows the generation of excitons only upon UV light irradiation, which is less than 5% of the solar spectrum, hence limiting its performance as a solar photocatalyst.…”