In this work, we demonstrate the use of direct ink writing (DIW) technology to create 3D catalytic electrodes for electrochemical applications. Hybrid MoS2/graphene aerogels are made by mixing commercially available MoS2 and graphene oxide powders into a thixotropic, high concentration, viscous ink. A porous 3D structure of 2D graphene sheets and MoS2 particles was created after post treatment by freeze-drying and reducing graphene oxide through annealing. The composition and morphology of the samples were fully characterized through XPS, BET, and SEM/EDS. The resulting 3D printed MoS2/graphene aerogel electrodes had a remarkable electrochemically active surface area (>1700 cm2) and were able to achieve currents over 100 mA in acidic media. Notably, the catalytic activity of the MoS2/graphene aerogel electrodes was maintained with minimal loss in surface area compared to the non-3D printed electrodes, suggesting that DIW can be a viable method of producing durable electrodes with a high surface area for water splitting. This demonstrates that 3D printing a MoS2/graphene 3D porous network directly using our approach not only improves electrolyte dispersion and facilitates catalyst utilization but also provides multidimensional electron transport channels for improving electronic conductivity.

The removal and immobilization of mercury(II) ions from industrial waste streams is a difficult and expensive problem requiring a robust extractant that is resistant to corrosive conditions. We have now developed an acid-resistant thiacrown polymer that has potential utility as a selective and cost-effective Hg2+ extractant. A new crown thioether, 2-hydroxymethyl-1,4,8,11,14-pentathiacycloheptadecane ([17] aneS5-OH), was synthesized through reaction of 2,3-dimercapto-1-propanol with 4,7,10-trithiatridecane-1,13-di-p-toluenesulfonate; then treated with thionyl chloride to form 2-chloromethyl-1,4,8,11,14-pentathiacycloheptadecane ([17] aneS5-Cl); followed by conversion to 2-(N-methyl)aminomethyl-1,4,8,11,14-pentathiacycloheptadecane ([17] aneS5-NHMe), through reaction with methylamine. The synthesis of the 4-vinylbenzyl-substituted thiacrown was readily accomplished by treating with 4-vinylbenzyl chloride. Co-polymerization of the 4-vinylbenzyl-substituted thiacrown with DVB (80% divinylbenzene) using AIBN as the radical initiator generated the highly cross-linked crown thioether polymer. The polymer based material was tested for Hg(II) extraction activity from acidic solutions. The material was found to extract 95+% of the Hg in a pH range of around 1.5 to over 6.0, with contact times of less than 30 min and in the presence of high concentration of competing ions such as Pb, Cd, Al, and Fe. The spent polymer could also be stripped of the Hg2+ and reused without sufficient loss of loading capacity. Characterization of the binding sites by XPS and XAS show only some of the S atoms in the thiacrown participate in the binding of Hg. Our results indicate this polymer has the potential to treat highly acidic wastes efficiently. This thiacrown polymer is far more effective in extracting Hg2+ from aqueous solution than previously reported Hg2+ extrac-tants, not only being very fast and efficient and selective, but also independent of pH.

Wide-band reflectrometry and ellipsometry have been used to determine the optical properties n and k of freshly polished uranium and of the epitaxial oxide layer, and also the rate of oxide growth in air. Results for uranium metal as well as for epitaxial oxide are compared with single wavelength ellipsometry literature values.

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