Enhancing the macroscopic polarization of CdS for piezo-photocatalytic water splitting

Piezo-photocatalytic hydrogen production from water splitting is emerging as a promising way to generate renewable energy, but is challenged by low efficiency and ambiguous understanding of mechanisms. Herein, the CdS phase junction (H/C-CdS) with interfacial structural distortion is applied for prominent piezo-photocatalytic H₂ evolution for the first time. Density functional theory (DFT) and second harmonic generation (SHG) demonstrate that the superior macroscopic polarity in H/C-CdS originates from the distortion of CdS₄ tetrahedron units at the interface between hexagonal CdS (H-CdS) and cubic CdS (C-CdS). The obvious enhanced macroscopic polarity of H/C-CdS largely boosts the separation of photogenerated electrons and holes with the elimination of the electrostatic screening produced in CdS phase junction. An encouraging piezo-photocatalytic H₂ evolution rate of 3.19 mmol·g⁻¹·h⁻¹ is delivered by H/C-CdS in pure water in the absence of any co-catalyst, which is 1.4 and 5.3 times higher than those of H-CdS (2.31 mmol·g⁻¹·h⁻¹) and C-CdS (0.59 mmol·g⁻¹·h⁻¹), respectively. Additionally, the value-added oxidation product H₂O₂ is produced in piezo-photocatalysis. This work firstly discloses macroscopic polarization enhancement induced by phase junction system on improvement of piezo-photocatalytic H₂ evolution of CdS.