Electronic properties and photocatalytic water splitting with high solar-to-hydrogen efficiency in a hBNC/Janus WSSe heterojunction: First-principles calculations

Currently, designing and exploring a photocatalyst with an interfacial electric field for hydrogen production from water splitting is crucial. Hence, based on first-principles calculations, we first calculate the electronic properties of the two-dimensional hexagonal boron nitride (hBN)/Janus WSSe heterojunction. However, the inherent energy band conformational defects of the hBN/Janus WSSe heterojunction inhibit the efficiency of photocatalytic. To solve this problem, we doped $\mathrm{C}=\mathrm{C}$ bonds on the monolayer hBN to tune the band gap. The research shows that the transition from the traditional type-I band alignment to the type-II band alignment can be achieved through different contracting methods between monolayer hexagonal boron nitride carbon (hBNC) and monolayer Janus WSSe. Notably, the hBNC/SWSe heterojunction is a direct Z-scheme photocatalyst and has high carrier mobility. Compared with the hBNC/SeWS heterojunction, the hBNC/SWSe heterojunction shows higher reduction reaction overpotential (${\ensuremath{\chi}}_{{\mathrm{H}}_{2}}=2.56\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$) and oxidation reaction overpotential (${\ensuremath{\chi}}_{{\mathrm{O}}_{2}}=0.83\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$) under acidic conditions. Furthermore, the hBNC/SWSe heterojunction has a high quantum efficiency and solar hydrogen production efficiency (33.31%). Gibbs free energy calculations confirm that both oxidation evolution reaction and hydrogen evolution reaction are exothermic reactions and can proceed spontaneously under the external potential provided by photogenerated carriers. These results suggest that the hBNC/SWSe heterojunction has potential applications in visible-light-driven water splitting.