Tuning Catalyst Selectivity for Ammonia vs Hydrogen: An Investigation into the Coprecipitation of Mo and Fe Sulfides

Ironsulfides are key materials in metalloprotein catalysis.One interesting aspect of iron sulfides in biology is the incorporationof secondary metals, for example, Mo, in nitrogenase. In this work,we examined the materials resulting from the coprecipitation of molybdenumwith iron sulfides using X-ray absorption spectroscopy (XAS). It wasobserved that the selectivity of reduction products depends on theamount of molybdenum, with the presence of approximately 10% Mo optimizingammonium/ammonia (NH4 (+)/NH3) productionfrom NO2 (-) and minimizing competitivehydrogen (H-2) formation. Ironsulfides are key materials in metalloprotein catalysis. Oneinteresting aspect of iron sulfides in biology is the incorporationof secondary metals, for example, Mo, in nitrogenase. These secondarymetals may provide vital clues as to how these enzymes first emergedin nature. In this work, we examined the materials resulting fromthe coprecipitation of molybdenum with iron sulfides using X-ray absorptionspectroscopy (XAS). The materials were tested as catalysts, and directreductants using nitrite (NO2 (-)) and protons(H+) as test substrates. It was found that Mo will coprecipitatewith iron as sulfides, however, in distinct ways depending on thestoichiometric ratios of Mo, Fe, and HS-. It wasobserved that the selectivity of reduction products depends on theamount of molybdenum, with the presence of approximately at 10% Mooptimizing ammonium/ammonia (NH4 (+)/NH3) production from NO2 (-) and minimizingcompetitive hydrogen (H-2) formation from protons (H+) with a secondary reductant.

Automated summary

Ironsulfides are key materials in metalloprotein catalysis. One interesting aspect is their incorporation of secondary metals, such as Mo. The selectivity of reduction products depends on the amount of Mo present, with approximately 10% Mo optimizing NH4 (+)/NH3 production from NO2 (-) and minimizing competitive H-2 formation.