The Role of the Metal Element in Layered Metal Phosphorus Triselenides upon Their Electrochemical Sensing and Energy Applications

The number of layered materials seems to be ever-growing, from mono- to multielement, with affiliates and applications being tested continuously. Chalcogenophosphites, also designated as metal phosphorus chalcogenides (MPX_n), have attracted great interest because of not only their magnetic properties but also promising capabilities in energy applications. Herein, bulk crystals of different layered metal triselenophosphites, with a general formula MPSe₃ (M = Cd, Cr, Fe, Mn, Sn, Zn), were synthesized. Structural and morphological characterization was performed prior to testing their electrochemical performance. From the set of ternary layered materials, FePSe₃, followed by MnPSe_3, yielded the highest efficiency for the hydrogen evolution reaction (HER) both in acidic and alkaline media with good stability after 100 cycles. MnPSe₃ also holds the lowest oxidation potential for cysteine, although this is due to the presence of MnO₂ in the structure as detected by X-ray photoelectron spectroscopy. For the oxygen evolution reaction, the best performance was observed for FePSe₃, although the stability of the material was not as good as in the case of HER. These findings have profound implications in the application of these layered ternary compounds in energy-related fields.