Metastable Facet-Controlled Cu 2 WS 4 Single Crystals with Enhanced Adsorption Activity for Gaseous Elemental Mercury

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Sulfur trioxide (SO 3 ) is an unstable pollutant, and its removal from the gas phase of industrial flue gas remains a significant challenge. Herein, we propose a reverse conversion treatment (RCT) strategy to reduce S(VI) in SO 3 to S(IV) by combining bench-scale experiments and theoretical studies. We first demonstrated that metastable sulfides can break the S−O bond in SO 3 , leading to the re-formation of sulfur dioxide (SO 2 ). The RCT performance varied between mono-and binary-metal sulfides, and metastable CuS had a high SO 3 conversion efficiency in the temperature range of 200−300 °C. Accordingly, the introduction of selenium (Se) lowered the electronegativity of the CuS host and enhanced its reducibility to SO 3 . Among the CuSe 1−x S x composites, CuSe 0.3 S 0.7 was the optimal RCT material and reached a SO 2 yield of 6.25 mmol/g in 120 min. The low-valence state of selenium (Se 2− /Se 1− ) exhibited a higher reduction activity for SO 3 than did S 2− /S 1− ; however, excessive Se doping degraded the SO 3 conversion owing to the re-oxidation of SO 2 by the generated SeO 3 2− . The density functional theory calculations verified the stronger SO 3 adsorption performance (E ads = −2.76 eV) and lower S−O bond breaking energy (E a = 1.34 eV) over CuSe 0.3 S 0.7 compared to those over CuS and CuSe. Thus, CuSe 1−x S x can serve as a model material and the RCT strategy can make use of field temperature conditions in nonferrous smelters for SO 3 emission control.

Section: Resultsmentioning

confidence: 98%

Reverse Conversion Treatment of Gaseous Sulfur Trioxide Using Metastable Sulfides from Sulfur-Rich Flue Gas

Hong

Pang

et al. 2022

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“…The corresponding calculated result was approximately 21.60 mg•g −1 , which was higher than that of many reported mercury sorbents 28,29 (Table 1) and about 9 times higher than that of the Cu 2 WS 4 single crystals. 24 Meanwhile, for the purpose of comparison, Cu 2 WS 4 -200 °C-72 h, Cu 2 WS 4 @COF-200 °C-72 h, Cu 2 WS 4 -120 °C-72 h (6 h), and Cu 2 WS 4 @COF-120 °C-72 h (24 h) were synthesized by tuning the hydrothermal reaction conditions and used as references in Figure 4b. As expected, the Cu 2 WS 4 @COF-120 °C-6 h composite showed the highest removal activity in terms of the normalized adsorption capacity.…”

Section: Hg 0 Adsorptionmentioning

confidence: 99%

“…Moreover, TpPa-2-COF integrated with α-Fe 2 O 3 was chosen for the construction of a Z-scheme heterostructured system, which showed an optimal hydrogen evolution rate without any noble metal co-catalyst participating. 23 Based on our previous work, 24 well-facet-controlled Cu 2 WS 4 single crystals have been fabricated and showed facetdependent adsorption performance for Hg 0 . However, the sorbent only performed well at low temperatures, and the adsorption capacity was small.…”

Section: Introductionmentioning

confidence: 99%

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Engineering of Defect-Rich Cu₂WS₄ Nano-homojunctions Anchored on Covalent Organic Frameworks for Enhanced Gaseous Elemental Mercury Removal

Wang

Zhang

et al. 2022

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Fabricating two-dimensional transition-metal dichalcogenide (TMD)-based unique composites is an effective way to boost the overall physical and chemical properties, which will be helpful for the efficient and fast capture of elemental mercury (Hg 0 ) over a wide temperature range. Herein, we constructed a defect-rich Cu 2 WS 4 nano-homojunction decorated on covalent organic frameworks (COFs) with abundant S vacancies. Highly well-dispersed and uniform Cu 2 WS 4 nanoparticles were immobilized on COFs strongly via an ion preanchored strategy, consequently exhibiting enhanced Hg 0 removal performance. The saturation adsorption capacity of Cu 2 WS 4 @ COF composites (21.60 mg•g −1 ) was 9 times larger than that of Cu 2 WS 4 crystals, which may be ascribed to more active S sites exposed in hybrid interfaces formed in the Cu 2 WS 4 nanohomojunction and between Cu 2 WS 4 nanoparticles and COFs. More importantly, such hybrid materials reduced adsorption deactivation at high temperatures, having a wide operating temperature range (from 40 to 200 °C) owing to the thermostability of active S species immobilized by both physical confined and chemical interactions in COFs. Accordingly, this work not only provides an effective method to construct uniform TMD-based sorbents for mercury capture but also opens a new realm of advanced COF hybrid materials with designed functionalities.

“…The sulfur coordination environment governs the amount and species of unsaturated sulfur over the surface of metal sulfides, which has a high relationship with crystal structure. − Yang et al reported that the crystallinity degree of ZnS could affect the status and amount of sulfur on the surface. In addition, by modulating the crystal nucleation and growth of metal sulfides, abundant defects and unsaturated edge sites can be directly created, which allows the formation of more surface-active centers. , These results pointed out the importance of crystal structure in determining the Hg 0 capture activity of CuS.…”

Section: Introductionmentioning

confidence: 99%

Controllable Disordered Copper Sulfide with a Sulfur-Rich Interface for High-Performance Gaseous Elemental Mercury Capture

Cao

Xiang

et al. 2022

Copper sulfide (CuS) has received increasing attention as a promising material in gaseous elemental mercury (Hg 0 ) capture, yet how to enhance its activity at elevated temperature remains a great challenge for practical application. Herein, simultaneous improvement in the activity and thermal stability of CuS toward Hg 0 capture was successfully achieved for the first time by controlling the crystal growth. CuS with a moderate crystallinity degree of 68.8% showed a disordered structure yet high thermal stability up to 180 °C. Such disordered CuS can maintain its Hg 0 capture activity stable during longtime test at a wide temperature range from 60 to 180 °C and displayed strong resistance to SO 2 (6%) and H 2 O (8%). The significant improvement can be attributed to the synergistic effect of a moderately crystalline nature and a unique sulfur-rich interface. Moderate crystallinity guarantees the thermal stability of CuS and the presence of abundant defects, in which copper vacancy enhances significantly the Hg 0 capture activity. The sulfur-rich interface enables CuS to provide plentiful highly active S x 2− sites for Hg 0 adsorption. The interrelation between structure, reactivity, and thermal stability clarified in this work broadens the understanding toward Hg 0 oxidation and adsorption over CuS and provides new insights into the rational design and engineering of advanced environmental materials.