Recent developments in Ti-based nanocatalysts for electrochemical nitrate-to-ammonia conversion

Abstract

Recently, electrochemical NO₃⁻-to-NH₃ conversion via the nitrate reduction reaction (NO₃⁻RR) has received much attention because it is regarded as an available option for sewage treatment and ammonia synthesis under mild conditions. Exploring promising electrocatalysts with low cost, reduced overpotential, high yield rate and faradaic efficiency toward NH₃, and sufficient stability is the most crucial factor for NO₃⁻-to-NH₃ conversion and energy efficiencies. Considering the advantages of being nontoxic and having wide availability, outstanding stability, hydrogen evolution inertness, and mature fabrication techniques, titanium-based (mainly metallic Ti- and TiO₂-based) nanomaterials have emerged as potential candidates for NO₃⁻-to-NH₃ conversion over a wide pH range. This review summarizes the overview of the NO₃⁻RR and fundamental insights into metallic Ti and TiO₂, and clarifies the relationship among the design strategy, material structure, and performance enhancement. Furthermore, the recent progress in next-generation Ti-based nanomaterials is discussed, including Ti-based MXene and single atomic catalysts. Finally, the challenges and future directions of the NO₃⁻RR and Ti-based nanocatalysts are elucidated. This review aims to provide some inspiration for developing effective electrocatalysts for electrochemical NO₃⁻-to-NH₃ conversion.