Peter B. Kreider

Visible-light-sensitive Na-doped p-type flower-like ZnO photocatalysts synthesized via a continuous flow microreactor

A Na-doped p-type flower-like ZnO photocatalyst (Na:ZnO) that is highly visible-light-sensitive in air at room temperature was synthesized by a continuous flow microreactor, where NaOH was used as both the precipitating and doping agent. The results of various characterization techniques (XPS, ICP, ToF-SIMS, XRD, and HRTEM) indicated that the Na ions have been successfully doped into the ZnO lattice. The Na:ZnO demonstrated a much higher photocatalytic degradation rate of methylene blue under simulated sunlight (λmax = 494 nm) than the rates obtained from commercially available TiO2 photocatalysts (P-25) and pure ZnO. This much enhanced rate is likely a result of increased surface defect sites associated with oxygen when Na replaces Zn in the crystal structure. A possible mechanism of the photocatalytic degradation of methylene blue on the Na:ZnO is suggested.

Plasmonics-enhanced metal–organic framework nanoporous films for highly sensitive near-infrared absorption

Combined plasmonic nanocrystals and metal–organic framework thin-films are fabricated for sensing gases in the near-infrared range. This nanocomposite thin-film shows a highly sensitive response in near-infrared absorption, which is attributed to preconcentration of gas molecules in metal–organic framework pores causing close proximity to the electromagnetic fields at the plasmonic nanocrystal surface.

Continuous synthesis of colloidal chalcopyrite copper indium diselenide nanocrystal inks

A continuous synthetic method in a micro-tubular reactor is introduced for synthesizing mono-disperse and solution-stable chalcopyrite colloidal copper indium diselenide nanocrystal (CuInSe2 NC) inks with potential scalability. It was found that the morphologies of the CuInSe2 NCs were dependent on the Cu/In/Se composition. The NC morphology changed from spherical to hexagonal to trigonal with increasing In or Se content, whereas trigonal morphologies synthesized at high temperature yielded chalcopyrite CuInSe2 NCs. A laboratory-scale photovoltaic device with 1.9% efficiency under AM1.5G illumination was also fabricated to verify the utility of these inks.

Two-step continuous-flow synthesis of CuInSe2 nanoparticles in a solar microreactor

A novel method of copper indium diselenide nanoparticle (CuInSe2 NP) synthesis using a two-step, continuous flow, solar microreactor is reported here. This method allows for exceedingly fast heating and short reaction times using only radiative heat transfer from simulated, concentrated solar radiation. Chalcopyrite and sphalerite CuInSe2 phases have both been synthesized by changing nucleation temperature and residence time through the solar microreactor, with higher nucleation temperatures and longer residence times allowing for the formation of the chalcopyrite CuInSe2 phase.

Characterization of Cotton Ball-like Au/ZnO Photocatalyst Synthesized in a Micro-Reactor

Noble metal/metal oxide nanostructures are an efficient system in photocatalysis. Continuous and scalable production of advanced particle systems will be a requirement for commercial-scale deployment for many applications, including photocatalysis. In this work, Au/ZnO structures were synthesized in a continuous flow micro-reactor at room temperature and the detailed characteristics of the product indicate a specific cotton ball-like core-shell microstructure that showcases specific advantages compared to traditional batch synthesis methods. The formation pathway of the core-shell Au/ZnO structures is discussed with the pH-dependent speciation diagram, and photocatalytic activity was assessed under simulated sunlight, demonstrating the enhanced performance of the cotton ball-like Au/ZnO microstructures in photocatalytic dye degradation. This work describes the application of microreaction technology in the continuous production of metal/metal oxide photocatalysts.

Solar-thermal Water Splitting Using the Sodium Manganese Oxide Process & Preliminary H2A Analysis

There are three primary reactions in the sodium manganese oxide high temperature water splitting cycle. In the first reaction, Mn2O3 is decomposed to MnO at 1,500°C and 50 psig. This reaction occurs in a high temperature solar reactor and has a heat of reaction of 173,212 J/mol. Hydrogen is produced in the next step of this cycle. This step occurs at 700°C and 1 atm in the presence of sodium hydroxide. Finally, water is added in the hydrolysis step, which removes NaOH and regenerates the original reactant, Mn2O3. The high temperature solar-driven step for decomposing Mn2O3 to MnO can be carried out to high conversion without major complication in an inert environment. The second step to produce H2 in the presence of sodium hydroxide is also straightforward and can be completed. The third step, the low temperature step to recover the sodium hydroxide is the most difficult. The amount of energy required to essentially distill water to recover sodium hydroxide is prohibitive and too costly. Methods must be found for lower cost recovery. This report provides information on the use of ZnO as an additive to improve the recovery of sodium hydroxide.