Hydridic and electrocatalytic properties of hypo-hyper-d-electronic combinations of transition metal intermetallic phases

Abstract

Hydridic and electrocatalytic properties of hypo-hyper-d-electronic combinations of transition metals in their intermetallic phases and alloys for the hydrogen storage, hydridic batteries and its electrode reactions (HELR) have been considered in the light of Fermi dynamics (or the electronic density of states), work function and the Brewer or Miedema intermetallic bonding theory (structural factors). It has been pointed out that such an intermetallic hypo-hyper-d-electronic interaction of transition metals (or the doped effect of a hyper-d- upon the bulk or surface of a hypo-d-electronic metal, or vice versa), which leads to the defined optimal mutual (bulk or surface) electronic density of states for both hydridic storage and/or electrocatalytic reaction (cathodic evolution (HER) and/or anodic oxidation (HOR) of hydrogen), imposes the same catalytic effect as the Non-Faradaic promotion by induced polarization, or the so-called NEMCA effect (Non-Faradaic Electrochemical Modification of Catalytic Activity). The main impact has been imposed on the most promising hydridic battery system (Ti-Ni, crystalline and sintered), as well as on typical electrocatalytic issues (Mo-Co, Mo-Ni, Zr-Ni). It has also been inferred that each phase diagram of a hypo-hyper-d-electronic combination of transition metals behaves in both the hydridic and electrocatalytic sense as the part of Periodic Table: intermetallic phases and alloys between two pure constituents obey typical volcano plots for both hydridic and catalytic activity in accordance with the changes in their electronic density of states and well-defined crystal structure, thereby resulting in intermetallic bonding effectiveness and a mutual work function.