Surface engineering of TiO2-CuO heterojunctions to optimize photocatalytic De-NOx performance

Abstract

Engineering the interfacial architecture of semiconductor-based heterojunctions is essential to maximize their functional performance. Herein, a rationally designed colloidal assembly route based on electrostatic interactions between TiO2 and CuO nanoparticles is proposed to improve their dispersion within composite powders and to optimize the resulting heterojunction performance for De-NOx photocatalysis. Unlike conventional approaches involving dry powders mixing, the proposed colloidal methodology enables precise surface charge adaptation, improved blending homogeneity, and enhanced physical interfacial contact between the phases. Composite powders with varying TiO2:CuO ratio were processed via both colloidal and mechanical routes to systematically elucidate the role of the processing strategy in governing interfacial architecture and photocatalytic efficiency, in a field in which this heterostructure has never been previously applied, NOx abatement. All samples exhibited activity toward NO abatement under irradiation; however, the colloidally prepared TiO2-CuO 1:0.25 (CT1:0.25) sample demonstrated the highest overall performance, achieving remarkable NO removal (88 %) with minimal NO2 emissions, corresponding to a superior selectivity of 98 % compared to benchmark TiO2 P25. Moreover, certain composites exhibited persistent photocatalysis in darkness, with CT1:0.25 again showing the most pronounced effect. FESEM-EDS images, XPS, BET, and EPR analysis herein included highlight that controlled colloidal surface engineering is not merely a greener processing alternative but an effective strategy to enhance interfacial coupling and electronic interaction in semiconductor heterojunctions. By enabling improved control over particle dispersion, interfacial contact, and phase distribution, this processing strategy provides a robust platform for tailoring semiconductor heterojunctions toward enhanced photocatalytic performance in environmental remediation applications.