Catalytic performance on the water decontamination and the water-splitting electrolysis of new phosphite salts (enH2)[M(H2O)6](HPO3)2 (M=Co, Ni and Mg)

Three new organic–inorganic hybrid phosphites salts, namely, (enH2)[M(H2O)6](HPO3)2, with [M = Co (1), Ni (2) and Mg (3), and “en” refers to ethylenediamine C2N2H8] have been synthesized at room temperature by the slow evaporation method. The solid-state structures were solved from single crystal X-ray diffraction data. These compounds are isostructural, all crystallizing in the orthorhombic system, space group, Pbca (no 61). The FTIR spectroscopy shows the expected bands of ethylenediamine (en), water molecules, and hydrogen-phosphite oxoanion groups. The thermal stability until 100 °C of the three compounds was confirmed using combined analyses (TGA/DTA, powder X-ray diffraction and Raman spectroscopy). Two catalytic activity performances were investigated: the catalytic efficiency on the water decontamination of the three compounds by the reduction of three nitrophenol isomers and the Hydrogen Evolution Reaction (HER) in an alkaline environment. The three hybrid compounds turned out to be very efficient new catalysts for reducing the three nitrophenol isomers. The fastest electron transport and the most favorable HER reaction kinetics are displayed by (enH2)[Ni(H2O)6](HPO3)2, while the highest current density with the lowest overpotential was obtained for (enH2)[Co(H2O)6](HPO3)2.