Exfoliated Layered Manganese Trichalcogenide Phosphite (MnPX₃, X = S, Se) as Electrocatalytic van der Waals Materials for Hydrogen Evolution

Layered metal trichalcogen phosphites, also entitled as metal phosphorus chalcogenides (MP X 3 ), have regained abundant interest, not only due to their magnetic properties, but also due to promising performances in energy storage and conversion. Herein, two different layered manganese trichalcogen phosphites, MnPX 3 ( X = S, Se), are synthetized and submitted to shear force exfoliation. Structural and morphological characterization point to the fact that exfoliated MP X 3 (exf‐MnP X 3 ) undergo mainly a downsizing process, alongside with delamination. Layered exf‐MnPSe 3 has the lowest onset potential for hydrogen evolution reaction (HER) in both media. In acidic media, a comparative improvement of 350 mV is observed for exf‐MnPSe 3 relative to the bulk MnPSe 3 . The materials stability as electrocatalysts is also tested for HER in a wide pH range, in which exf‐MnPSe 3 has a good stability after 100 cycles. The improved performance of exf‐MnPSe 3 can be correlated with the lower relative abundance of Mn and P oxides detected in the Mn 2p and P 2p core levels. Such materials show a great promise for future in a hydrogen‐based economy.