Functional graphitic carbon nitride/hydroxyapatite heterojunction for robust formaldehyde removal at ambient temperature

Ambient-temperature catalytic removal of formaldehyde (HCHO) hazard has been currently reckoned as a practicable and promising approach for abating indoor HCHO which severely haunts the human's health. Catalyst with high-effectiveness and low-cost is a pivotal parameter determining the reliability and availability of this strategy. Herein, bifunctional graphitic carbon nitride/hydroxyapatite heterostructures (g-C3N4/HAP) were developed for indoor HCHO removal at ambient temperature. The optimal catalyst (g-C3N4/HAP-20) displayed enhanced HCHO removal efficiency of 36.6% and conversion (into CO2) efficiency of 28.4% within 2 h, compared with g-C3N4 (18.0% and 24.0%) and HAP (36.2% and similar to 0%). Indoor fluorescent light accelerated HCHO elimination and its subsequent decomposition into CO2 over g-C3N4/HAP-20, delivering a HCHO removal efficiency of 82.7% and conversion efficiency of 100% within 2 h. Various characterizations and theoretical calculation reveal that g-C3N4/HAP possessed superoxide radicals and unpair electrons which were responsible for HCHO removal at ambient temperature; and a S-scheme heterostructure remarkably benefited the charge transfer and the photogenerated carriers' separation, and consequently upgraded HCHO catalytic oxidation under indoor fluorescent-light illumination. This work offers a potent way to construct noble-metal free advanced catalysts with multi-functionality for indoor pollutant purification.