Regulating bimetallic active centers for exploring the structure–activity relationship toward high-performance photocatalytic nitrogen reduction

Abstract

Photocatalytic ammonia (NH3) synthesis from N2 is a strategy conducive to carbon neutrality because it avoids high energy consumption and high carbon emission process in the industrial synthesis of NH3. However, the structure–activity relationship of bimetallic active centers in heterogeneous catalysts is still unclear for high-performance photocatalytic nitrogen reduction reaction (pNRR). Here, we explore in-depth the structure–activity relationship of high-performance pNRR by regulating the semi- or full-encapsulated structure model formed by the noble metal nanoparticles (Pd, Au, and Pt) and mesoporous TiO2 nanorods (NRs). Further mechanism studies revealed that the Ti–Pd bimetallic active centers at the interface of semi-encapsulated palladium-decorated mesoporous TiO2 NRs possesses ultra-high adsorption energy, which can effectively weaken the triple bond of N2 and reduce the activation energy barrier of pNRR process. Accordingly, the optimal se-Pd/m-TiO2 NRs (2.71%) photocatalyst demonstrates a NH3 production rate of up to 635.73 μg/gcat./h, reaching a high apparent quantum efficiency of 0.37% at 375 nm under mild conditions. This work not only opens an avenue to expand high-performance catalysts for N2 photofixation under mild conditions via regulating bimetallic centers but also offers atomic-level insights for understanding the internal pNRR procedure.