Photoelectrocatalytic Conversion of Nitrates to Ammonia: Effect of Proton Donor

Changes in farming techniques have facilitated the movement of nitrogen-containing species, making converting nitrate into ammonia (fertilizer) highly desirable. Recently, we introduced a photosystem comprising NiO/Au plasmon/TiO2 that can selectively convert nitrate to ammonia at neutral pH and room temperature using visible light in a photo-electrochemical approach. The study evaluated the role of adding alcohol to the overall process activity and selectivity. Adding small quantities of alcohol to the electrolyte leads to changes in the catalytic behaviour, which cannot be attributed exclusively to improvement in counter-electrode reaction kinetics. Analysis of product Faradaic efficiency and photo-current measurements revealed that alcohols act as proton donors in nitrate/nitrite reduction, possibly through a concerted proton-couple electron transfer mechanism. These initial findings offer new handles for nitrate reduction to ammonia efficacy at neutral pH. Ultimately, this opens up avenues for agricultural practices that recycle nutrients, improve process circularity, and reduce fertilizer costs, thus contributing to economic sustainability.