Layered Metal Thiophosphite Materials: Magnetic, Electrochemical, and Electronic Properties

Beyond graphene, transitional metal dichalcogenides, and black phosphorus, there are other layered materials called metal thiophosphites (MPS_x), which are recently attracting the attention of scientists. Here we present the synthesis, structural and morphological characterization, magnetic properties, electrochemical performance, and the calculated density of states of different layered metal thiophosphite materials with a general formula MPS_x, and as a result of varying the metal component, we obtain CrPS₄, MnPS₃, FePS₃, CoPS₃, NiPS₃, ZnPS₃, CdPS₃, GaPS₄, SnPS₃, and BiPS₄. SnPS₃, ZnPS₃, CdPS₃, GaPS₄, and BiPS₄ exhibit only diamagnetic behavior due to core electrons. By contrast, trisulfides with M = Mn, Fe, Co, and Ni, as well as CrPS₄, are paramagnetic at high temperatures and undergo a transition to antiferromagnetic state on cooling. Within the trisulfides series the Néel temperature characterizing the transition from paramagnetic to antiferromagnetic phase increases with the increasing atomic number and the orbital component enhancing the total effective magnetic moment. Interestingly, in terms of catalysis NiPS₃, CoPS₃, and BiPS₄ show the highest efficiency for hydrogen evolution reaction (HER), while for the oxygen evolution reaction (OER) the highest performance is observed for CoPS₃. Finally, MnPS₃ presents the highest oxygen reduction reaction (ORR) activity compared to the other MPS_x studied here. This great catalytic performance reported for these MPS_x demonstrates their promising capabilities in energy applications.