The advantages of transition metal chelated by methylene diphosphonate and its doped on hydroxyapatite crystals: High h-production with low metal usage, electro-catalysis possibility and reuse capability

Abstract

In this study, the catalysis design is demonstrated by a metal ion-containing acid molecular group and its doped with coordination bonding to the support material. Inspired by the working principle of radiopharmaceuticals performed in the human body, the catalyst design takes into account all chemical processes from the interaction of the pharmaceutical molecule with the skeletal system to its dissociation. The catalyst structures are both structure consisting of two methylene diphosphonate (medronic acid), CH2(PO(OH)2)2, which the chelate atom is cobalt for electro-catalysis and the structure resulting in its doped to the Hydroxyapatite (HAp) crystal (Ca10(PO4)6(OH)2) for hydrogen evolution reaction (HER) catalyst. The fact that two medronic acids (Co@ 2 (CH2(PO(OH)2)2) containing a cobalt element prefer to hold on the HAp crystal rather than each other, ensuring the homogeneous spreading of this molecular structure on the HAp surface. This state is shown with the GFN1xTB (Geometries, Frequencies, and Non-covalent interactions Tight Binding) model. In addition, the preference of externally added metal ions to on the cobalt ion centered between the medronic acids creates Metal Atom Stations (MAS) on the HAp. Since the system is similar to the effect in the human body, vitamins and antioxidants (like H2 gas) play a role in removing the medronic structure from HAp, providing the formation of a high activity region on cobalt. The produced H2 creates a bubble effect on the solid surface in the liquid environment, reducing the Co-O(HAp) interaction and occurs a trigger effect in H2 production. This may be considered as a control mechanism in hydrogen production. Also, the change in the cobalt bonding number with the bubble effect and/or the asymmetrical geometry resulting from the support material-molecule interaction suggests the possibility of electro-catalysis. In addition, if the subsequently doped Ni atoms are present between the chelated molecules, they form a weak chelate with the compound. Weak chelation is significantly affected by temperature and temperature plays a role in cleaning the excess metals that disrupt the homogeneity in catalysis. In this case, the reuse efficiency of the catalysis is increased.