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

Electrochemical nitrate (NO 3 − ) reduction reaction (NO 3 RR) possesses two-pronged properties for sustainable ammonia (NH 3 ) synthesis and mitigating NO 3 − contamination in water. However, the sluggish kinetics for the direct eight-electron NO 3 − -to-NH 3 conversion makes a formidable challenge to develop efficient electrocatalysts. Herein, we report a heterostructure of Co 3 O 4 nanosheets decorated TiO 2 nanobelt array on titanium plate (Co 3 O 4 @TiO 2 /TP) as an efficient NO 3 RR electrocatalyst. Both experimental and density theory calculations reveal that the heterostructure of Co 3 O 4 @TiO 2 establishes a built-in electric field which can optimize the electron migration kinetics, as well as facilitate the adsorption and fixation of NO 3 − on the electrode surface, ensuring the selectivity to NH 3 . As expected, the designed Co 3 O 4 @TiO 2 /TP exhibits a remarkable Faradaic efficiency of 93.1 % and a remarkable NH 3 yield as high as 875 μmol h −1 cm −2 , superior to Co 3 O 4 /TP and TiO 2 /TP. Significantly, it also demonstrates strong electrochemical durability.