(126g) Novel Electrocatalysts for Nitrogen Oxides Reduction at Ambient Conditions

Mitigating nitrogen oxides (NO_x) emissions is critical to tackle global warming and improve air quality.¹Conventional NO_x abatement technologies for emission control suffer from a low efficiency at near ambient temperatures.² Electrochemical NO_x reduction reaction is an alternative approach to convert NO_x into benign N₂ or useful chemicals (e.g., NH₃), powered by renewable electricity. For environmental applications, N₂ is the desired product because it is non-toxic and can be emitted directly to the atmosphere, whereas NH₃ is preferable when local generation of fertilizer is needed for crops. More importantly, Electrochemical NO_x reduction reaction can be conducted at high reaction rates at ambient temperature because it is driven by applied potential (i.e., electrical energy), as opposed to high temperatures and pressures in conventional. In this work, we investigate a series of transition metal catalysts for electrocatalytic reduction of gaseous nitric oxide (NO) and nitrous oxide (N₂O) at ambient condition in a gas-fed electrolyzer configuration.³ Fe, Co, Ni, Cu, Pd, Ag, and Pt were chosen as representative metal catalysts because they are common catalysts for electroreduction reactions, such as oxygen reduction reaction and hydrogen evolution reaction (HER). To gain mechanistic insights, NO partial pressure and pH effects are investigated on Pd and Cu, representing catalysts selective for N₂ and NH₃ formation, respectively. Furthermore, combining various electrochemical experiments and operando flow electrolyzer mass spectrometry (FEMS), we determined reaction pathways and rate determining steps (RDSs) of NO electroreduction on Pd and Cu.

References

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3. Ko, B. H., Hasa, B., Shin, H., Zhao, Y. R. & Jiao, F.* Electrochemical reduction of gaseous nitrogen oxides on transition metals at ambient conditions. Amer. Chem. Soc. 144, 1258-1266 (2022).