2 Search Results

Olefin epoxidation, an important industrial reaction, often uses hazardous oxidants, causing challenges in waste disposal. Here, we demonstrate the use of water as an oxidant by a plasmon-assisted electrochemical strategy. The electrocatalyst is comprised of a hybrid of a water oxidation catalyst, manganese oxide, and plasmonic gold nanoparticles. Visible-light irradiation of the electrocatalyst enhanced the epoxidation of 4-styrenesulfonate 5-fold as compared to dark conditions at the same temperature. From electrochemical analyses conducted under plasmon excitation conditions, complemented by real-time time-dependent density functional tight binding simulations, it is found that the plasmonic boost of the electrochemical styrene epoxidation is due tomore » energetic holes generated by the excitation of localized surface plasmon resonances of gold nanoparticles. These photogenerated holes activate adsorbed water for oxidation and enhance the binding of 4-styrenesulfonate at interfacial sites. Here, this work demonstrates a proof of concept and establishes the mechanistic basis for plasmon-assisted activation of water as an O atom source for electrochemical epoxidations.« less

Sonicated emulsive water microdroplets (SEWMs) accelerate and enable a variety of catalyst-free chemical transformations. However, significant unanswered questions remain regarding the chemical intermediates they form and their possible redox origin. In this study, we identified dissolved O₂ as the primary originator of reactive oxygen species (ROS) such as OH• and H₂O_2. We uncovered the role of dissolved O₂ redox by using a combination of microelectrochemical methods to detect H₂O₂, isotopic methods to identify the source of H₂O₂, and a combination of electron spin resonance and the DMPO spin trap to detect radicals such as OH•. Notably, we found that H₂O₂more » production is correlated with O₂ content via a reduction pathway enabled by a sufficiently large reducing power that can additionally generate H₂ and even perform Pb electroless deposition on Au and Cu metal substrates. Building on our findings, continuous O₂ bubbling of SEWMs showed accumulation of H₂O₂ up to ∼88 mM in the aqueous phase within 1 h of sonication, demonstrating the scale-up promise of this method. Distinct to sonochemistry of a single phase, this study advances our understanding of the confluence of redox and chemical reaction mechanisms within SEWMs as a biphasic system. This insight paves the way for improving their reaction kinetics, yield, and selectivity, positioning these attractive redox microreactors as alternatives to traditional electrolyzers.« less