Stacking-switching of silicon-based two-dimensional diamane structures to enhance photocatalytic water splitting performance

Through first-principles calculations, we design and screen a series of Janus silicon-based two-dimensional (2D) diamane Si₄HX (X = F, Cl and Br) structures as promising piezoelectric photocatalysts for water splitting. The transitions from the initial to the final states of the Si₄HX monolayers lead to enhanced physical properties that characterize their photocatalytic performances. Notably, the reversal and enhancement of the intrinsic in-plane polarizations more efficiently drive in-plane carrier migrations, thereby enhancing carrier mobility. Furthermore, the extensive out-of-plane built-in electric fields combined with excellent piezoelectricity of the Si₄HX monolayers further generate the strain-enhanced intrinsic electric fields, which effectively drive the out-of-plane migrations of photogenerated carriers and thus suppress their recombination. These effects synergistically enhance the photocatalytic water-splitting performances of the Si₄HX monolayers, and pave a viable pathway to overcome the limitations prevalent in conventional 2D photocatalysts.