Rational Design and Characterization of Direct Z-Scheme Photocatalyst for Overall Water Splitting from Excited State Dynamics Simulations

Direct Z-scheme heterostructure photocatalysts possess tremendous potential to solar-driven overall water splitting, but how to rationally design and comprehensively characterize high-efficient direct Z-scheme heterostructures remains a great challenge. Herein, we report the design of metal-free C3B/C3N heterostructure through constructing a p-n heterojunction as a potential direct Z-scheme photocatalyst for overall water splitting by combining first-principles and excited state dynamics simulations. Our calculations show that the strong interlayer interaction in C3B/C3N p-n heterostructure provides a large built-in electric field with about 0.4 V/angstrom and strong interface nonadiabatic coupling which significantly accelerates the recombination of carriers with weak redox capacity (similar to 0.5 ps) and retards the lifetime of carriers with strong redox capacity (similar to 4 ps). Meanwhile, the B atoms, serving as Lewis acid sites, are good catalytic centers to trap water molecules. The hydrogen reduction reaction and complex four-electronic water oxidation reaction can happen smoothly on the C3B and C3N surface, respectively, without additional overpotential and cocatalyst. This work not only provides a potential metal-free direct Z-scheme photocatalyst for overall water splitting, but also paves the way to rational design high-performance direct Z-scheme photocatalysts.