RGO/Cu2O-CuO nanocomposite as a visible-light assisted photocatalyst for reduction of organic nitro groups to amines

Fabrication of Hollow and Hierarchical CuO Micro-Nano Cubes Wrapped by Reduced Graphene Oxide as a Prospective Anode for SIBs

In this study, hollow and hierarchical CuO micro-nano cubes wrapped by reduced graphene oxide (H-CuO MNCs@rGO) were designed and successfully fabricated via a novel three-step wet-chemical method. Benefiting from its unique hollow and hierarchical micro-nano structures, H-CuO MNCs@rGO exhibited significantly enhanced electrochemical Na+ storage performance when utilized as anode material for sodium-ion batteries (SIBs). Specifically, H-CuO MNCs@rGO demonstrated a specific capacity of 380.9 mAh g-1 in the initial reversible cycle and a capacity retention of 218.9 mAh g-1 after 150 cycles at a current density of 300 mA g-1. Furthermore, through the dominant pseudocapacitive behavior, an optimized rate capability of 221.2 mAh g-1 at 800 mA g-1 can be obtained for H-CuO MNCs@rGO. The comprehensive Na+ storage properties of H-CuO MNCs@rGO obviously exceeded those of hollow CuO cubes (H-CuO MNCs) and bulk CuO anodes. Such enhanced Na+ storage performances of H-CuO MNCs@rGO can be attributed to its reasonable hollow and hierarchical micro-nano structures, which provide abundant redox active sites, shorten Na+ migration pathway, buffer volume expansion, and improve electronic/ionic conductivity during sodiation/desodiation process. Our strategy provides a facile and innovative approach for the design of CuO with rational micro-nano structure as a high-performance anode for SIBs, which would also be a guiding way for tailoring transition metal oxides in other scalable and functional applications.

Ultrasensitive Bio-H2S Gas Sensor Based on Cu2O-MWCNT Heterostructures

Developing a respiratory analysis disease diagnosis platform for the H2S biomarker has great significance for the real-time detection of various diseases. However, achieving highly sensitive and rapid detection of H2S gas at the parts per billion level at low temperatures is one of the most critical challenges for developing portable exhaled gas sensors. Herein, Cu2O-multiwalled carbon nanotube (MWCNT) heterostructures with excellent gas sensitivity to H2S at room temperature and a lower temperature were successfully synthesized by a facile two-dimensional (2D) electrodeposition in situ assembly method. The combination of Cu2O and MWCNTs via the principle of optimal conductance growth not only reduced the initial resistance of the material but also provided an ideal interfacial barrier structure. Compared to the response of the pure Cu2O sensor, that of the Cu2O-MWCNT sensor to 1 ppm of H2S increased nearly 800 times at room temperature, and the response time decreased by more than 500 s. In addition to the excellent sensitivity with detection limits as low as 1 ppb, the Cu2O-MWCNT sensor was extremely selective with low-temperature adaptability. The sensor had a response value of 80.6 to 0.1 ppm of H2S at -10 °C, which is difficult to achieve with sensors based on oxygen adsorption/desorption mechanisms. The sensor was used for the detection of real oral exhaled breath, confirming its feasibility as a real-time disease monitoring sensor. The Cu2O-MWCNT heterostructures maximized the advantages of the individual components and laid the experimental foundation for future applications of highly sensitive portable breath analysis platforms for monitoring H2S.

An Integrated Electrochemical System for Synergistic Cathodic Nitrate Reduction and Anodic Sulfite Oxidation

Electrochemical reduction of nitrate has broad application prospects. However, in traditional electrochemical reduction of nitrate, the low value of oxygen produced by the anodic oxygen evolution reaction and the high overpotential limit its application. Seeking a more valuable and faster anodic reaction to form a cathode-anode integrated system with nitrate reaction can effectively accelerate the reaction rate of the cathode and anode, and improve the utilization of electrical energy. Sulfite, as a pollutant after wet desulfurization, has faster reaction kinetics in its oxidation reaction compared to the oxygen evolution reaction. Therefore, this study proposes an integrated cathodic nitrate reduction and anodic sulfite oxidation system. The effect of operating parameters (cathode potential, initial NO₃^--N concentration, and initial SO₃^2--S concentration) on the integrated system was studied. Under the optimal operating parameters, the nitrate reduction rate in the integrated system reached 93.26% within 1 h, and the sulfite oxidation rate reached 94.64%. Compared with the nitrate reduction rate (91.26%) and sulfite oxidation rate (53.33%) in the separate system, the integrated system had a significant synergistic effect. This work provides a reference for solving nitrate and sulfite pollution, and promotes the application and development of electrochemical cathode-anode integrated technology.

A uniformly anchored zirconocene complex on magnetic reduced graphene oxide (rGO@Fe3O4/ZrCp2Cl x (x = 0, 1, 2)) as a novel and reusable nanocatalyst for synthesis of N-arylacetamides and reductive-acetylation of nitroarenes

In this study, a crafted zirconocene complex on rGO@Fe3O4 as a novel magnetic nanocatalyst was synthesized and then characterized using FT-IR, SEM, EDX, VSM, ICP-OES, TGA, BET and MS analyses. Next, catalytic activity of the prepared nanocomposite rGO@Fe3O4/ZrCp2Cl x (x = 0, 1, 2) towards successful reduction of aromatic nitro compounds to arylamines using N2H4·H2O (80%) was investigated. The examined nanocatalyst also showed perfect catalytic activity for reductive-acetylation of aromatic nitro compounds to the corresponding N-arylacetamides without isolation of the prepared in situ amines using the N2H4·H2O/Ac2O system. Furthermore, acetylation of the commercially available arylamines to the corresponding N-arylacetamides was carried out by acetic anhydride in the presence of the rGO@Fe3O4/ZrCp2Cl x (x = 0, 1, 2) nanocomposite. All reactions were carried out in refluxing EtOH as a green solvent to afford the products in high yields. The obtained results exhibited that the nanocomposite of rGO@Fe3O4/ZrCp2Cl x (x = 0, 1, 2) showed a great catalytic activity in comparison to rGO and rGO@Fe3O4 as the parent constituents. Recovery and reusability of rGO@Fe3O4/ZrCp2Cl x (x = 0, 1, 2) were also examined for 8 consecutive cycles without significant loss of the catalytic activity. This establishes the sustainable anchoring of the zirconocene complex on the surface and mesopores of the rGO@Fe3O4 nanohybrid system.