Increase 50-time catalyst mass activity from revealing true reactions in proton exchange membrane electrolysis.

Novel LGDLs remarkably reduce losses and reveals unprecedented rapid electrochemical reactions.

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3We report a mechanistic DRIFTS in-situ study of NO 2 , NO + O 2 and NO adsorption on a 4 commercial Cu-CHA catalyst for NH 3 -SCR of NOx. Both pre-reduced and pre-oxidized catalyst 5 samples were investigated with the aim to clarify mechanistic aspects of the NO oxidation to NO 2 6 as a preliminary step towards the study of the Standard SCR reaction mechanism at low 7 temperatures. Nitrosonium cations (NO + , N oxidation state = +3) were identified as key surface 8 intermediates in the process of NO (+2) oxidation to NO 2 (+4) and nitrates (+5). While NO + and 9 nitrates were formed simultaneously upon catalyst exposure to NO 2 , nitrates evolved consecutively 10 to NO + when the catalyst was exposed to NO + O 2 , suggesting that nitrite-like species, and not NO 2 , 11 are formed as the primary products of the NO oxidative activation over Cu-CHA. Upon catalyst 12 exposure to NO only, i.e. in the absence of gaseous O 2 , NO + and then nitrates were formed on a 13 preoxidized sample but not on a prereduced one, which demonstrates the red-ox nature of the NO 14 oxidation mechanism. The negative effect of H 2 O on NO + and nitrates formation was also clearly 15 established. Assuming small Cu clusters, in the form of Cu dimers, as the active sites for NO 16 oxidation to NO 2 , we propose a mechanism which reconciles all the experimental observations. In 17 particular, we show that such a mechanism also explains the observed kinetic effects of H 2 O, O 2 18 and NO 2 on the NO oxidation activity of the investigated Cu zeolite catalyst. 19 20 21