FERMI DYNAMICS AND SOME STRUCTURAL BONDING ASPECTS OF ELECTROCATALYSIS FOR HYDROGEN EVOLUTION

There has been inferred that the electrocatalytic activity of both ind ividual transition metals and their intermetallic phases and alloys fo r hydrogen evolution primarily correlates with the electronic density of states and obeys typical laws of catalysis reflected in the first p lace in the volcano plots along the periodic table. Due to the fact th at the intermetallic bonding effectiveness of hypo-hyper-d-electronic transition metal composite electrocatalysts correlates in a straightfo rward manner with their electrocatalytic activity, such state of evide nce strongly suggests the Fermi energy, as a typical atomic binding en ergy, for the basis in investigation and correlation of electrocatalyt ic activity. Since the Fermi wavevector represents the individual and collective (alloys and intermetallic phases) bulk property of the avai lable electronic number density [or its concentration, n, ie, k(F) = ( 3 pi(2)n)(1/3)], and in a straightforward manner correlates with the e lectronic density of states at the Fermi level, and thereby defines al l metallic properties of a metal (and intermetallics) as ''a solid wit h a Fermi surface'', including electrocatalytic features, it has been taken as the main parameter to correlate with the exchange current den sity in the hydrogen evolution reaction (her). It has been inferred th at 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 ele ctrocatalytic activity. The Fermi wave-vector therefore is considered as the main governing parameter to estimate and predict electrocatalyt ic activity of intermetallic electrocatalysts of transition metals. Th e latter is implied within the Thomas-Fermi approximation based upon t he assumption that a local internal chemical potential of electrons (r ead the electrochemical potential or consequently the redox potential of an electrode) can be defined as a function of the electron concentr ation at that point. Electrode potential and kinetic relations imply t he latter as the macroscopic law.