Rhombohedral Boron Monosulfide as a p-Type Semiconductor

Abstract

Two-dimensional materials have wide ranging applications in electronic devices and catalysts owing to their unique properties. Boron-based compounds, which exhibit a polymorphic nature, are an attractive choice for developing boron-based two-dimensional materials. Among them, rhombohedral boron monosulfide (r-BS) has recently attracted considerable attention owing to its unique layered structure similar to that of transition metal dichalcogenides and a layer-dependent bandgap. However, experimental evidence that clarifies the charge carrier type in the r-BS semiconductor is lacking. In this study, we synthesized r-BS and evaluated its performance as a semiconductor by measuring the Seebeck coefficient and photo-electrochemical responses. The properties unique to p-type semiconductors were observed in both measurements, indicating that the synthesized r-BS is a p-type semiconductor. Moreover, a distinct Fano resonance was observed in Fourier transform infrared absorption spectroscopy, which was ascribed to the Fano resonance between the E(2) (TO) phonon mode and electrons in the band structures of r-BS, indicating that the p-type carrier was intrinsically doped in the synthesized r-BS. These results demonstrate the potential future application prospects of r-BS.

Electrocatalytic Mechanisms for an Oxygen Evolution Reaction at a Rhombohedral Boron Monosulfide Electrode/Alkaline Medium Interface

“…Finally, we briefly discuss the carrier-doping for r-BS. The previous experimental measurements reported that the synthesized r-BS shows the p-type character. , Thus, to consider the catalytic mechanism of r-BS, we considered the flat band potential E FB of r-BS. This is because the space charge layer owing to the band-bending is an important kinetic descriptor to obtain high-performance OER electrocatalysts with the semiconductor electrode …”

“…Thus, the graphene nanoplate in r-BS + G only plays a role in the conductive assistant, and active sites of the r-BS + G catalyst are considered to be located at the basal surface. Furthermore, several experimental measurements of r-BS synthesized under high temperatures and pressures indicates the p-type semiconductor character, , which implies the synthesized r-BS contains some defects. The possibility of surface defects promoting the ORR activity is pointed out by the previous experimental and theoretical studies for the other materials. − Therefore, we modeled the r-BS electrode surface by the basal surface using the repeated 4 × 4 slab model with and without the surface defects, as shown in Figure a,b.…”

“…Rhombohedral boron monosulfide (r-BS) is a two-dimensional-layered material with a tunable band gap similar to the transition-metal dichalcogenide. , After its successful synthesis, r-BS has attracted significant attention from theoretical and experimental researchers owing to its physical properties. − A recent study has demonstrated that r-BS combined with a graphene nanoplate (r-BS + G) is a promising OER catalyst in an alkaline medium because of the large redox current with a lower overpotential . In r-BS + G, the graphene nanoplate mainly acts as a conductive assistant.…”