Bio-inspired in situ activation strategy of photocatalysts by CO2 mineralization in cement-based materials

Abstract Semiconductor photocatalysis integrated into cement-based materials offers a promising route for mitigating urban NO x pollution; however, achieving high activity and selectivity with low-cost cocatalysts remains challenging. Inspired by natural biomineralization, this study proposed a CO 2 mineralization-driven in situ activation strategy that synergistically leveraged the catalytic functionality of cement-based substrates. A MgO-TiO 2 -CaCO 3 (MTC) ternary composite catalytic system was fabricated through a two-step synthesis process, in which MgO-doped TiO 2 acted as a novel precursor to trigger CaCO 3 nucleation and growth, thereby enabling synergistic cocatalytic interactions. The optimized MTC-10 exhibited a NO removal efficiency nearly twice that of pristine TiO 2 , while reducing NO 2 generation by half. Mechanistic investigations revealed that the synergistic coupling of MgO and CaCO 3 , as alkaline earth metal oxides/compounds, introduced oxygen vacancies and enhanced surface alkalinity, inhibiting the formation of toxic NO 2 /N 2 O 4 intermediates. Density functional theory (DFT) calculations further demonstrated that CaCO 3 functioned as a “transfer hub”, promoting charge redistribution, accelerating carrier migration, and enhancing reactive oxygen species (ROS) generation. These processes were crucial for the complete oxidation of NO, helping to suppress the formation of of byproducts such as NO 2 and promoting the transformation of nitrite into more stable nitrate species. This work establishes a novel CO 2 mineralization-driven strategy for boosting TiO 2 photocatalysis in cement-based materials, offering a dual-benefit pathway for CO 2 utilization and selective NO x abatement.