Understanding the Synergy between Fe and Mo sites in the Nitrate Reduction Reaction on a Bio-Inspired Bimetallic MXene Electrocatalyst

Angew Chem Int Ed Engl. 2023 Oct 31:e202313746. doi: 10.1002/anie.202313746. Online ahead of print.ABSTRACTMo- and Fe-containing enzymes catalyze the reduction of nitrate and nitrite ions in nature. Inspired by this activity, we study here the nitrate reduction reaction (NO3RR) catalyzed by an Fe-substituted two-dimensional molybdenum carbide of the MXene family, viz., Mo2CTx:Fe (Tx are oxo, hydroxy and fluoro surface termination groups). Mo2CTx:Fe contains isolated Fe sites in Mo positions of the host MXene (Mo2CTx) and features a Faradaic efficiency (FE) and an NH3 yield rate of 41% and 3.2 µmol h-1 mg-1, respectively, for the reduction of NO3- to NH4+ in acidic media and 70% and 12.9 µmol h-1 mg-1 in neutral media. Regardless of the media, Mo2CTx:Fe outperforms monometallic Mo2CTx owing to a more facile reductive defunctionalization of Tx groups, as evidenced by in situ X-ray absorption spectroscopy (Mo K-edge). After surface reduction, a Tx vacancy site binds a nitrate ion that subsequently fills the vacancy site with O* via oxygen transfer. Density function theory calculations provide further evidence that Fe sites promote the formation of surface O vacancies, which are identified as active sites and that function in NO3RR in close analogy to the prevailing mechanism of the natural Mo-based nitrate reductase enzymes.PMID:37907396 | DOI:10.1002/anie.202313746

Source: Angewandte Chemie - October 31, 2023 Category: Chemistry Authors: Daniel F Abbott Yuanzi Xu Denis A Kuznetsov Priyank Kumar Christoph R M üller Alexey Fedorov Victor Mougel Source Type: research