Fermi dynamics and some structural bonding aspects of electrocatalysis for hydrogen evolution

Abstract

There has been inferred that the electrocatalytic activity of both individual transition metals and their intermetallic phases and alloys for hydrogen evolution primarily correlates with the electronic density of states and obeys typical laws of catalysis reflected in the first place in the volcano plots along the periodic table. Due to the fact that the intermetallic bonding effectiveness of hypo-hyper- d-electronic transition metal composite electrocatalysts correlates in a straightforward manner with their electrocatalytic activity, such state of evidence strongly suggests the Fermi energy, as a typical atomic binding energy, for the basis in investigation and correlation of electrocatalytic activity. Since the Fermi wave-vector represents the individual and collective (alloys and intermetallic phases) bulk property of the available electronic number density [or its concentration, n, ie, k F = (3π 2 n) 1 3 ], and in a straightforward manner correlates with the electronic density of states at the Fermi level, and thereby defines all metallic properties of a metal (and intermetallics) as “a solid with a Fermi surface”, including electrocatalytic features, it has been taken as the main parameter to correlate with the exchange current density in the hydrogen evolution reaction ( her). It has been inferred that the Fermi wave-vector, as the main electronic feature of metal and intermetallic phases, has already been implicitly comprised in kinetic relations of the exchange current density, otherwise decisive for electrocatalytic activity. The Fermi wave-vector therefore is considered as the main governing parameter to estimate and predict electrocatalytic activity of intermetallic electrocatalysts of transition metals. The latter is implied within the Thomas-Fermi approximation based upon the assumption that a local internal chemical potential of electrons (read the electrochemical potential or consequently the redox potential of an electrode) can be defined as a function of the electron concentration at that point. Electrode potential and kinetic relations imply the latter as the macroscopic law.