Oxygen vacancies in Bi₂WO₆ enable robust nitrate reduction reaction catalysis

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Nitrate contamination in water poses environmental and health risks.
• Efficient catalytic reduction of nitrate to less harmful products is crucial.
• Bismuth-based oxides are explored for electrochemical applications.

Purpose of the Study:

• To evaluate the performance of Bismuth tungstate (Bi$_{2}$WO$_{6}$) for nitrate reduction.
• To compare the efficiency of Bi$_{2}$WO$_{6}$ against its constituent oxides, Bi$_{2}$O$_{3}$ and WO$_{3}$.

Main Methods:

• Electrochemical characterization of Bi$_{2}$WO$_{6}$ for nitrate reduction.
• Operando Raman spectroscopy to study reaction intermediates.
• Theoretical calculations to elucidate the catalytic mechanism.

Main Results:

• Bi$_{2}$WO$_{6}$ achieved a faradaic efficiency of 62.0% for nitrate reduction at -0.3 V vs. RHE.
• This represents a 1.4-fold and 1.8-fold improvement over Bi$_{2}$O$_{3}$ and WO$_{3}$, respectively.
• The reaction pathway was identified as nitrate to ammonia: *NO$_{3}$→*NO$_{2}$→*NO→*NOH→*HNOH→*H$_{2}$NOH→*NH$_{3}$.

Conclusions:

• Bi$_{2}$WO$_{6}$ is a highly efficient electrocatalyst for nitrate reduction.
• The study elucidates the complete reaction pathway, offering insights for catalyst design.
• This finding contributes to developing effective methods for mitigating nitrate pollution.