Unveiling selective nitrate reduction to ammonia with Co₃O₄ nanosheets/TiO₂ nanobelt heterostructure catalyst

Electrochemical nitrate (NO₃^-) reduction reaction (NO₃RR) possesses two-pronged properties for sustainable ammonia (NH₃) synthesis and mitigating NO₃^- contamination in water. However, the sluggish kinetics for the direct eight-electron NO₃^--to-NH₃ conversion makes a formidable challenge to develop efficient electrocatalysts. Herein, we report a heterostructure of Co₃O₄ nanosheets decorated TiO₂ nanobelt array on titanium plate (Co₃O₄@TiO₂/TP) as an efficient NO₃RR electrocatalyst. Both experimental and density theory calculations reveal that the heterostructure of Co₃O₄@TiO₂ establishes a built-in electric field which can optimize the electron migration kinetics, as well as facilitate the adsorption and fixation of NO₃^- on the electrode surface, ensuring the selectivity to NH₃. As expected, the designed Co₃O₄@TiO₂/TP exhibits a remarkable Faradaic efficiency of 93.1 % and a remarkable NH₃ yield as high as 875 μmol h^-1 cm^-2, superior to Co₃O₄/TP and TiO₂/TP. Significantly, it also demonstrates strong electrochemical durability.