Plasmonic Cu 9 S 5 Nanonets for Microwave Absorption

Zuo

Advanced Energy Materials

et al. 2021

As a bridge between nanocrystal catalysts and single‐atom catalysts, single‐unit‐cell catalysts seem at first glance to be unavailable for catalysis due to quantum effects and synthetic difficulties. Here, 24 nm Cu9S5 nanowires are synthesized via the LaMer pathway. Interestingly, when polyoxometalate (POM) clusters are introduced during the nucleation process, the 0.9 nm Cu9S5 nanowires are finally formed via covalent co‐assembly, analog to A–B–A–B‐type block co‐polymerization in the polymer field (“A” and “B” represent Cu9S5 unit cells and POM clusters, respectively). Multiple characterizations show that Cu9S5 exists as single‐unit‐cell structure. Therefore, each unit cell can work as an isolated active site. The single‐unit‐cell structure exhibits higher electrocatalytic activity and Faradaic efficiency (FE) of formic acid (82.0% at −0.8 V vs reversible hydrogen electrode (RHE)) during CO2 electroreduction, while the nanocrystal structure generates HCOO−, methanol, and ethanol with low FEs. This study suggests that the single‐unit‐cell catalyst displays great potential for precise catalysis by the finite size effect.

Section: Resultssupporting

confidence: 81%

Single‐Unit‐Cell Catalysis of CO₂ Electroreduction over Sub‐1 nm Cu₉S₅ Nanowires

Zuo

Advanced Energy Materials

et al. 2021

“…In general, the complex permittivity (ε r = ε ′‐ iε″ ) and complex permeability (μ r = μ′‐iμ″ ) are the two key electromagnetic parameters for determining the microwave absorbing performance of EMW absorbers. [ 3a,23 ] The ε′ and μ′ represent the storage capability of EMW, while the ε″ and μ″ reflect the attenuation ability of EMW, respectively. Due to the nonmagnetic characteristics of TMDs, the ε r were measured ≈1.0 and ≈0 as shown in Figure S4, Supporting Information, thereby suggesting a negligible magnetic loss in MoS 2 absorbers.…”

Section: Resultsmentioning

confidence: 99%

“…[ 1,2 ] Thus, the search for EMW absorbers with lightweight, high efficiency, and wide absorption frequency ranges has been always pursued. [ 2b,c,3 ] As the widely known 2D transition metal dichalcogenides (TMDs), molybdenum disulfide (MoS 2 ), which consists of S‐Mo‐S triple layers, has attracted considerable attentions in electronic and optoelectronic devices owing to their unique electrical and optical properties. [ 4 ] In the area of electromagnetic attenuation, the dielectric‐dominated EMW absorbing MoS 2 sheet (NMS) absorber was firstly reported in 2015, [ 5 ] which exhibited the promising attenuation performance compared to the traditional carbon‐based dielectric absorbers.…”

Section: Introductionmentioning

confidence: 99%

Phase Manipulating toward Molybdenum Disulfide for Optimizing Electromagnetic Wave Absorbing in Gigahertz

Ning

Jiang

Ding

et al. 2021

Adv Funct Materials

176

Molybdenum disulfide (MoS 2 ) has been proved to be a potential electromagnetic wave (EMW) absorber. However, the limited EMW attenuation mechanisms and conductivity have always been recognized as the major challenges impeding their further developments. In this study, a new dielectric tuning strategy giving rise to high EMW attenuation performance by manipulating phase content (with 0, 24, 50, and 100 wt% 1T phase) toward MoS 2 is demonstrated. The greatly introduced 2H/1T interfaces facilitate the dipole distribution dynamics, and the metal-semiconductor mixed phase enhances the electron transfer ability. Benefiting from the structural merits, the MoS 2 with 50 wt% 1T absorber delivers the maximum reflection loss of −45.5 dB and effective absorbing bandwidth of ≈3.89 GHz, corresponding to nearly ten times higher than that of pure 2H counterpart. Moreover, the Computer Simulation Technology (CST) simulation and Lorentz transmission electron microscope are performed to visualize the structural advantages of MoS 2 absorbers with mixed 2H/1T phases. By manipulating the phase compositions, this study provides a deep understanding and opens an avenue in developing efficient and high performance transition metal dichalcogenides (e.g., WS 2 , MoSe 2 , and WSe 2 ) absorbers.

ACS Sustainable Chem. Eng.

“…We used XPS analysis to study the surface chemical composition of the copper sulfide samples. In Figure a, the main high-resolution Cu 2p spectrum of Cu 9 S 5 displays two major peaks at 932.5 and 952.3 eV that correspond to the Cu 2p 3/2 and Cu 2p 1/2 in the Cu 9 S 5 , respectively. Further deconvolution illustrates the presence of two peaks centered at 934.4 and 953.8 eV from Cu 2+ and two additional peaks near 935.7 and 955.4 eV probably from CuSO 4 .…”

Section: Resultsmentioning

confidence: 99%

Phase-Dependent Photocatalytic Activity of Bulk and Exfoliated Defect-Controlled Flakes of Layered Copper Sulfides under Simulated Solar Light

Telkhozhayeva

Konar

Lavi

et al. 2021

Sunlight-driven photocatalysis is an environmentally friendly approach to solve ecological issues. The development of simple yet sufficiently stable photocatalytic materials capable of responding to the full-spectrum light remains challenging. Here, we demonstrate the phase transformations of bulk copper sulfides from digenite (Cu 9 S 5 ) to djurleite (Cu 1.97 S) and low chalcocite (Cu 2 S) by the reactive thermal annealing during ambient pressure chemical vapor deposition, followed by their top-down exfoliation. Using multiple techniques, we confirm that monoclinic Cu 2 S is primarily formed at higher temperatures or greater reaction times and using a reducing atmosphere. We measured the average thickness to be approximately 4 nm for the exfoliated flakes with relatively large lateral sizes of up to 10 μm. We tested the three phases of bulk copper sulfides and their exfoliated forms as photocatalysts for dye degradation under simulated solar light irradiation. Exfoliated Cu 2 S flakes exhibited superior photocatalytic activity (0.007 min −1 ), roughly twice higher than that of bulk chalcocite, which could be predominantly attributed to their 2D structure and also 2D planar defects, which could serve as active centers for dye photodegradation. Our study paves the way for developing nextgeneration full-spectrum-responsive 2D copper sulfide photocatalysts for environmental decontamination.