Precisely tuning band gaps of graphene/h-BN lateral heterostructures toward enhanced photocatalytic hydrogen evolution.

Constructing heterojunctions is a proven strategy for developing efficient photocatalytic hydrogen evolution catalysts. In this work, we design graphene/hexagonal boron nitride (h-BN) lateral heterostructures that combine graphene's exceptional charge transport with h-BN's stability. Using state-of-the-art many-body green's function theory (MBGFT) simulations, we establish a band engineering framework through dimensional control, demonstrating that precise modulation of graphene and h-BN domain sizes enables continuous visible-spectrum band gap tuning for efficient hydrogen generation. The prototypical 66BN-33Gr heterostructure exemplifies this tunability, exhibiting an optimal optical band gap of 2.00 eV with superior photon harvesting characteristics. Notably, this catalyst demonstrates remarkably low exciton binding energies in the visible region, ensuring efficient charge separation. Mechanistic studies of the hydrogen evolution reaction (HER) disclose an exceptionally small energy barrier (0.21 eV) in photoexcited states, thermodynamically favoring spontaneous hydrogen generation. Furthermore, the AA-stacked architecture exhibits remarkable band gap modulation capabilities, enabling broadband optical absorption spanning the visible to near-infrared spectral regions. These fundamental insights lay the theoretical foundation for rationally engineering graphene/h-BN heterostructures as efficient photocatalytic hydrogen evolution catalysts.