Cation Exchange Enables the Universal Synthesis of 2D Metal Selenides for Solar Hydrogen Conversion

Photocatalytic hydrogen production offers a promising solution to the global energy crisis, but the design of efficient photocatalysts remains challenging. Although two-dimensional (2D) metal selenides (MSe) show great potential, their controlled synthesis is limited by difficulties in tuning the composition and morphology. Herein, we present a cation exchange (CE) strategy for the synthesis of a diverse range of 2D MSe nanoplates utilizing Cu_2-xSe nanoplates as a sacrificial template. By leveraging CE, we successfully converted Cu_2-xSe nanoplates into 11 distinct MSe compounds, including ZnSe, CdSe, Co₉Se₈, Ni₃Se₄, PbSe, Ag₂Se, Zn_xCd_1-xSe, CuAgSe, CuInSe₂, Cu₂SnSe₃, and CuFeSe₂, while preserving their 2D morphology. Taking Zn_xCd_1-xSe nanoplates as an example, they exhibit strong visible-light absorption and superior solar-to-hydrogen conversion performance, attaining a rate of up to 14.52 mmol h^-1 g^-1. This work establishes a scalable and tunable approach for the synthesis of 2D MSe nanostructures, paving the way for advanced photocatalysts in solar-to-hydrogen energy conversion.