Theory-guided construction of Cu-O-Ti-Ov active sites on Cu/TiO2 catalysts for efficient electrocatalytic nitrate reduction
Electrocatalytic nitrate reduction reaction(NO3RR)has been capturing immense interest in the industrial application of ammonia synthesis,and it involves complex reaction routes accompanied by multi-electron transfer,thus causing a challenge to achieve high efficiency for catalysts.Herein,we customized the Cu-O-Ti-Ov(oxygen vacancy)structure on the Cu/TiO2 catalyst,identified through density functional theory(DFT)calculations as the synergic active site for NO3RR.It is found that Cu-O-Ti-Ov site facilitates the adsorption/association of NOx-and promotes the hydro-genation of NO3-to NH3 via adsorbed*H species.This effectively suppresses the competing hydro-gen evolution reaction(HER)and exhibits a lower reaction energy barrier for NO3RR,with the reac-tion pathways:NO3*→ NO2*→ HONO*→ NO*→*NOH →*N →*NH →*NH2→*NH3 →NH3.The optimized Cu/TiO2 catalyst with rich Cu-O-Ti-Ov sites achieves an NH3 yield rate of 3046.5μg h-1 mgcat1 at-1.0 V vs.RHE,outperforming most of the reported activities.Furthermore,the construction of Cu-O-Ti-Ov sites significantly mitigates the leaching of Cu species,enhancing the stability of the Cu/TiO2 catalyst.Additionally,a mechanistic study,using in situ characterizations and various comparative experiments,further confirms the strong synergy between Cu,Ti,and Ov sites,which is consistent with previous DFT calculations.This study provides a new strategy for designing efficient and stable electrocatalysts in the field of ammonia synthesis.
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