Unveiling heterointerface activation effects with different titanium dioxide crystal phases for electrocatalytic nitrate-to-ammonia reduction

Nitrate pollution poses severe risks to aquatic ecosystems and human health. The electrocatalytic nitrate reduction reaction (NITRR) offers a promising environmental and economic solution for nitrate pollution treatment and nitrogen source recovery; however, it continues to experience limited efficiency in neutral electrolytes. This study explores the heterointerface activation effects of TiO₂/Cu₂O heterogeneous catalysts with rutile (R-TiO₂) and anatase (A-TiO₂) phases and reveals that R-TiO₂ is an active crystal phase with high nitrate reduction performance. The R-TiO₂/Cu₂O catalyst removed 99.8 % of nitrate in 180 min and achieved an ammonia yield of 0.23 mmol h⁻¹ cm⁻² with a Faraday efficiency of 85.7 % in a neutral electrolyte. In situ characterisation and theoretical calculations revealed that heterointerface reconstruction and oxygen vacancy (O_V) formation overcome the poor electrical conductivity of R-TiO₂, enhance electron transfer, and optimize the active sites. Furthermore, the Cu-O-Ti bond at the interface significantly weakens the adsorption energy of the critical intermediate *NO₃, thereby facilitating NITRR. This study provides new insights into crystal phase modulation in catalyst design and offers innovative strategies for developing highly efficient NITRR electrocatalysts, paving the way for sustainable nitrate pollution treatment and nitrogen source recovery.