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Abstract The design ofN‐oxyl hydrogen atom transfer catalysts has proven challenging to date. Previous efforts have focused on the functionalization of the archetype, phthalimide‐N‐oxyl. Driven in part by the limited options for modification of this structure, this strategy has provided only modest improvements in reactivity and/or solubility. Our previous mechanistic efforts suggested that while the electron‐withdrawing carbonyls of the phthalimide are necessary to maximize the O−H bond dissociation enthalpy of the HAT product hydroxylamine and overall reaction thermodynamics, they undergo nucleophilic substitution leading to catalyst decomposition. In an attempt to minimize this vulnerability, we report the characterization ofN‐oxyl catalysts wherein the aryl ring in PINO is replaced with the combination of a substituted heteroatom and quaternary carbon. By rendering one carbonyl carbon less electrophilic and the other less sterically accessible, the correspondingN¹‐aryl‐hydantoin‐N³‐oxyl radical showed significantly higher stability than PINO as well as a modest improvement in reactivity. This proof‐of‐principle in new scaffold design may accelerate future HAT catalyst discovery and development. 

Abstract In this work, we demonstrate plasma‐catalytic synthesis of hydrogen and acrylonitrile (AN) from CH₄and N₂. The process involves two steps: (1) plasma synthesis of C₂H₂and HCN in a nominally 1:1 stoichiometric ratio with high yield up to 90% and (2) downstream thermocatalytic reaction of these intermediates to make AN. The effect of process parameters on product distributions and specific energy requirements are reported. If the catalytic conversion of C₂H₂and HCN in the downstream thermocatalytic step to AN were perfect, which will require further improvements in the thermocatalytic reactor, then at the maximum output of our 1 kW radiofrequency 13.56 MHz transformer, a specific energy requirement of 73 kWh kg_AN⁻¹was determined. The expectation is that scaling up the process to higher throughputs would result in decreases in specific energy requirement into the predicted economically viable range less than 10 kWh kg_AN⁻¹. 

This study explores the potential of using electrochemical (EC) methods for valorizing lignin, a lignocellulosic biomass cell wall component, into biofuels and high-value compounds. 

Nonthermal plasmas in contact with liquids have been shown to generate a variety of reactive species capable of initiating reduction–oxidation (redox) reactions at the electrochemically active plasma–liquid interface. In conventional electrochemical cells, selective redox chemistry is achieved by controlling the reduction potential at the solid electrode–electrolyte interface by applying a bias via an external circuit. In the case of plasma–liquid systems, an analogous means of tuning the reduction potential near the interface has not clearly been identified. When treated as a floating surface, the liquid is expected to adopt a net negative charge to balance the flux of hot electrons and relatively cold positive ions. The reduction potential near the plasma–liquid interface is hypothesized to be proportional to the floating potential, which can be approximated using an analytical model provided the plasma parameters are known. Herein, we present a framework for correlating the electron density and electron temperature of a noble gas plasma jet to the reduction potential near the plasma–liquid interface. The plasma parameters were acquired for an argon atmospheric plasma jet in contact with an aqueous solution by means of laser Thomson scattering. The reduction potential was determined using identical reference electrodes to measure the potential difference between the plasma–liquid interface and bulk solution. Interestingly, the measured reduction potentials near the plasma–liquid interface were found to be in good agreement with the model-predicted values determined using the plasma parameters obtained from the Thomson scattering experiments.