In‐Plane Palladium and Interplanar Copper Dual Single‐Atom Catalyst in Bulk‐Like Carbon Nitride for Cascade CO2 Photoreduction

Dual single‐atom catalysts (DSACs) are promising for breaking the scaling relationships and ensuring synergistic effects compared with conventional single‐atom catalysts (SACs). Nevertheless, precise synthesis and optimization of DSACs with specific locations and functions remain challenging. Herein, dual single‐atoms are specifically incorporated into the layer‐stacked bulk‐like carbon nitride, featuring in‐plane three‐coordinated Pd and interplanar four‐coordinated Cu (Pd1‐Cu1/b‐CN) atomic sites, from both experimental results and DFT simulations. Using femtosecond time‐resolved transient absorption (fs‐TA) spectroscopy, it is found that the in‐plane Pd features a charge decay lifetime of 95.6 ps which is much longer than that of the interplanar Cu (3.07 ps). This finding indicates that the in‐plane Pd can provide electrons for the reaction as the catalytically active site in both structurally and dynamically favorable manners. Such a well‐defined bi‐functional cascade system ensures a 3.47‐fold increase in CO yield compared to that of bulk‐like CN (b‐CN), while also exceeding the effects of single Pd1/b‐CN and Cu1/b‐CN sites. Furthermore, DFT calculations reveal that the inherent transformation from s–p coupling to d–p hybridization between the Pd site and CO2 molecule occurs during the initial CO2 adsorption and hydrogenation processes and stimulates the preferred CO2‐to‐CO reaction pathway. In‐plane three‐coordinated Pd and interplanar four‐coordinated Cu are incorporated into the layer‐stacked bulk‐like carbon nitride, forming a cascade effect. In‐plane Pd are the potential active sites with stronger electron reserve capability while the interplanar Cu facilitates the carrier transfer from the interior bulk to the exterior catalytic surface as the charge transfer channel.