A Electrocatalytic Reduction of N2O to

Electrocatalytic removal of N2O from industrial or automobile gas streams emitted to the atmosphere is a technologically important process [208], as is removal of N2O as a greenhouse gas. As a potentially useful application, it has been demonstrated that a fuel cell can be constructed based on the reduction of N2O coupled to the oxidation of H2 [209]. The two-electron reduction of N2O to N2 is very favorable from a thermodynamic standpoint (also see below), but the barrier to introduction of the first electron is quite high. For this reason, electrochemical reduction by sequential one-electron steps is unfavorable unless intermediates can be considerably stabilized. 

A number of transition metal complexes demonstrate electrocatalytic N2O reduction activity. Collman and coworkers [210] designed and prepared a series of binary or face-to-face metalloporphyrin complexes as catalysts that might be capable of binding N2O in between the two metal ions. They observed that the electrocatalytic rate of N2O reduction was sensitive to hydroxide, changes in the functionality of the porphyrin periphery and the presence of proton donors. 

Taniguchi and coworkers [211] reported that when using Ni complexes of macrocycHc polyamines like [15 or 14]ane N4  

Electrolysis at a nickel electrode (with no catalyst) led to N2 and H2 evolution, in contrast to the results with the nickel complex catalysts which gave N2 in close to 100% yield no significant amounts of H2 or NO were detected. 

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