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 (MPX3), 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, MnPX3 (X = S, Se), are synthetized and submitted to shear force exfoliation. Structural and morphological characterization point to the fact that exfoliated MPX3 (exf-MnPX3) undergo mainly a downsizing process, alongside with delamination. Layered exf-MnPSe3 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-MnPSe3 relative to the bulk MnPSe3. The materials stability as electrocatalysts is also tested for HER in a wide pH range, in which exf-MnPSe3 has a good stability after 100 cycles. The improved performance of exf-MnPSe3 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.