Atomic-scale evidence for highly selective electrocatalytic N-N coupling on metallic MoS₂

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Molybdenum sulfide (MoS₂) is a key transition-metal dichalcogenide (TMD) with tunable electrocatalytic properties.
• Phase engineering of MoS₂ can enhance its activity, but selectivity in complex reactions remains a challenge.
• Nitrite reduction to nitrous oxide is crucial for biological denitrification.

Purpose of the Study:

• To investigate the effect of MoS₂ phase engineering on the selectivity of nitrite reduction.
• To elucidate the atomic-scale mechanism behind phase-dependent selectivity in MoS₂ electrocatalysis.

Main Methods:

• Continuous-wave and pulsed electron paramagnetic resonance spectroscopy.
• Electrocatalytic experiments with pH-dependent selectivity measurements.
• Deuterium kinetic isotope effect analysis.

Main Results:

• Metallic 1T-MoS₂ exhibits a unique protonation site (pK_a ≈ 5.5) near the redox-active Mo site.
• This site facilitates sequential proton-electron transfer, inhibiting ammonium formation.
• The 1T-MoS₂ phase selectively promotes nitrous oxide production.

Conclusions:

• Phase engineering of MoS₂ significantly enhances selectivity for nitrous oxide production during nitrite reduction.
• Atomic-scale understanding of the protonation mechanism provides insights into selective electrocatalysis.
• This work expands the application of TMDs in selective electrochemical transformations.