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Reduction of nitric oxide was investigated using Cu electrodes in acid and neutral pH conditions. Analysis of Cu discs in stagnant electrolyte by Electrochemical Mass Spectrometry (EC-MS), revealed the favorable formation of ammonia (and hydrogen) in acidic electrolyte, while N 2 O and N 2 are formed in significant quantities at neutral conditions. Additional performance evaluation of Cu electrodes in hollow fiber geometry, was performed using 10 vol % NO in Ar supplied through the porous electrode structure and off-line determination of ammonia by 1 H NMR spectroscopy. The pH dependent performance of the Cu hollow fiber is in agreement with EC-MS data at low gas flow rates, showing the highest ammonia selectivity in acidic conditions. However, at relatively high gas flow rates, almost 90 % faradaic efficiency and a NH 3 production rate of 400 μmol h À 2 cm À 2 were obtained in neutral electrolyte at À 0.6 V vs RHE, likely due to enhanced availability of NO at the electrode surface, suppressing the hydrogen evolution reaction. This approach shows conversion of waste NO gas to valuable green fertilizer components is possible.

Online, on-chip measurement of nitric oxide (NO) in organ-on-chip devices is desired to study endothelial (dys) function under dynamic conditions. In this work, ruthenium oxide (RuOx) is explored as an amperometric NO sensor and its suitability for organ-on-chip applications. For testing purposes, diethylamine NONOate was used as chemical NO donor. The NONOate's NO generation and electrochemical oxidation of generated NO were confirmed by real-time electrochemical/mass-spectrometry. Using RuOx nanorods electrodes, we show that NO oxidation occurred at a lower onset potential (+675 mV vs. Ag/AgCl) than on bare Pt electrode (+800 mV vs. Ag/AgCl). Due to NO adsorption on the RuOx surface, NO oxidation also delivered a higher current density (33.5 nA.μM − 1 . cm -2 ) compared to bare Pt (19.6 nA.μM − 1 . cm -2 ), making RuOx nanorods a favourable electrode for NO sensing applications. The RuOx electrode's suitability for organ-on-chip applications was successfully tested by using the electrode to detect a few micromolar concentration of NO generated by endothelial cell culture. Overall, the RuOx nanorods proved to be suitable for organ-on-chip studies due to their high sensitivity and selectivity. Our chip-integrated electrode allows for online NO monitoring in biologically relevant in vitro experiments.

Non-efficient fertilizer use in agriculture causes nitrate runoff, polluting rivers and streams. This pollution can be mitigated by partially converting nitrate into ammonia – rebalancing the composition to ammonium nitrate,...

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In performing electrochemical reduction of CO2 over Cu electrodes, the anions present in solution typically do not participate in the formation of reaction products. NO3- is an exception, and previous reports indicate the formation of urea in certain process conditions. Here we demonstrate by use of Surface Enhanced Raman Spectroscopy and Electrochemical Mass spectrometry that simultaneous reduction of NO3- and CO2 on Cu surfaces forms carbon-nitrogen bonds in the form of cyanide. The Raman peak position of C≡N is dependent on the oxidation state of the Cu surface, and Cu-C≡N can be oxidized by anodic polarization yielding NO. More importantly, Cyanide likely forms soluble Cu-C≡N complexes, which cause catalyst surface instability. The implications of this observation for practical application of a process for electrochemical formation of urea, are discussed.

Electrochemical decarboxylation of acetic acid on boron-doped diamond electrodes (BDD) was studied as a possible means to decrease the acidity of pyrolysis oil. It is shown that decarboxylation occurs without...