Constructing Co@TiO2 Nanoarray Heterostructure with Schottky Contact for Selective Electrocatalytic Nitrate Reduction to Ammonia

Abstract

Electrochemical nitrate (NO3−) reduction reaction (NO3−RR) is a potential sustainable route for large-scale ambient ammonia (NH3) synthesis and regulating the nitrogen cycle. However, as this reaction involves multi-electron transfer steps, it urgently needs efficient electrocatalysts on promoting NH3 selectivity. Herein, a rational design of Co nanoparticles anchored on TiO2 nanobelt array on titanium plate (Co@TiO2/TP) is presented as a high-efficiency electrocatalyst for NO3−RR. Density theory calculations demonstrate that the constructed Schottky heterostructures coupling metallic Co with semiconductor TiO2 develop a built-in electric field, which can accelerate the rate determining step and facilitate NO3− adsorption, ensuring the selective conversion to NH3. Expectantly, the Co@TiO2/TP electrocatalyst attains an excellent Faradaic efficiency of 96.7% and a high NH3 yield of 800.0 µmol h−1 cm−2 under neutral solution. More importantly, Co@TiO2/TP heterostructure catalyst also presents a remarkable stability in 50-h electrolysis test.