Ultrafast carrier recombination in a BC6N/SnXY Z-scheme heterostructure for water splitting: insights from ground- and excited-state carrier dynamics

Abstract

To obtain environmentally friendly and economically viable clean energy in a water-based future energy economy, direct Z-scheme heterostructure photocatalysts with overall water-splitting potential are generally favored. However, there are still many limitations in judging the carrier migration pattern when only the method of a conventional built-in electric field is used. Here, a novel approach that combines the direction of the built-in electric field with excited-state nonadiabatic molecular dynamics to determine the pattern of carrier migration inside the structure is proposed. The conclusions indicate that the timescale of nonadiabatic electron–hole migration ensures a Z-scheme carrier migration pattern within the heterostructure, while the orientation of the built-in electric field significantly accelerates the rate of recombination between weak redox capacity carriers. Meanwhile, the presence of inherent dipoles within the heterostructure leads to movement of band edges, thereby enhancing the redox ability for the hydrogen evolution reaction (HER) and effectively meeting the requirements of the half-reaction for the band edges. Furthermore, four-electron oxidation reaction steps exhibit superior water-splitting potential in a solvation environment compared to vacuum conditions. This study introduces an efficient strategy for determining carrier migration patterns within heterostructures and offers insights into the design of novel Z-scheme heterostructures.