To overcome current serious energy and environmental issues, photocatalytic water splitting holds great promise because it requires only solar energy as an energy input to produce hydrogen. In this work, based on first-principle calculations, we studied the van der Waals heterostructure formed by PtS₂ and arsenene (Are) monolayers that were successfully synthesized on a large scale at high quality. From an analysis of the migration paths of photoinduced electrons and holes, a direct Z-scheme photocatalytic mechanism is demonstrated in this heterostructure. Furthermore, the PtS₂/Are direct Z-scheme heterostructure has decent band edge positions to promote the redox reaction to decompose water at pH 0. The interfacial charge difference and potential drop are presented, which further support the formation of a direct Z-scheme photocatalyst. More importantly, the PtS₂/Are heterostructure has quite high solar-to-hydrogen (STH) efficiency (49.32%), significantly enhanced compared with isolated PtS₂ (12.67%) or Are (10.34%) monolayers. This direct Z-scheme PtS₂/Are heterostructure with excellent STH efficiency suggests its promising application as a photocatalyst for water splitting.

Molecularly soft organic-inorganic hybrid perovskites are susceptible to dynamic instabilities of the lattice called octahedral tilt, which directly impacts their carrier transport and exciton-phonon coupling. Although the structural phase transitions associated with octahedral tilt has been extensively studied in 3D hybrid halide perovskites, its impact in hybrid 2D perovskites is not well understood. Here, we used scanning tunneling microscopy (STM) to directly visualize surface octahedral tilt in freshly exfoliated 2D Ruddlesden-Popper perovskites (RPPs) across the homologous series, whereby the steric hindrance imposed by long organic cations is unlocked by exfoliation. The experimentally determined octahedral tilts from n = 1 to n = 4 RPPs from STM images are found to agree very well with out-of-plane surface octahedral tilts predicted by density functional theory calculations. The surface-enhanced octahedral tilt is correlated to excitonic redshift observed in photoluminescence (PL), and it enhances inversion asymmetry normal to the direction of quantum well and promotes Rashba spin splitting for n > 1.

Although metal halide perovskites are increasingly popular for the next generation of efficient photovoltaic devices, the inevitable defects from the preparation process have become the notorious barrier to further improvement of performance, which increases non‐radiative recombination and lowers the power conversion efficiency of solar cells. Surface passivation strategies have been affirmed as one of the most practical approaches to suppress these defects. Therefore, it is necessary to have a detailed review on the surface passivation to reveal the improvements of the devices. Herein, the mechanism and recent advances of surface passivation have been systematically summarized with respect to various passivation approaches, including the Lewis acid–base, the low‐dimensional perovskite, inorganic molecules, and polymers. Finally, the review also offers the research trend and prospects of surface passivation.

CF ₃ PEAI, an amphipathic passivation agent, can passivate multiple perovskite defects leading to high performance and stability of perovskite solar cells.