Hydrogen Evolution Reaction
The hydrogen evolution reaction (HER) is the cathodic electrochemical reaction in which protons (or water) are reduced to molecular hydrogen at an electrode surface. Because it proceeds through a single adsorbed intermediate, adsorbed hydrogen, it is a common model reaction for relating catalytic activity to the strength with which an intermediate binds to the surface. See also Volcano plot and Hydrogen adsorption free energy.
Exchange-current trends across metals (2005)
Nørskov, Kitchin and coworkers compiled measured HER exchange currents for thirteen metals and explained their variation using DFT hydrogen chemisorption energies. Free energy diagrams at the equilibrium potential show that every step of HER on Pt is close to thermoneutral, which they identify as the main reason the Pt group metals are the best HER catalysts. They also computed water dissociation energies and concluded that Mo and W surfaces should be oxygen covered, so the measured currents on those metals likely reflect oxides (Nørskov et al. 2005). Summary: norskov2005.
Response to the Schmickler and Trasatti comment (2006)
In a reply to criticism of their 2005 paper on HER exchange-current trends ((Nørskov et al. 2005)), Nørskov, Kitchin and coworkers argue that the value of their approach lies in computing hydrogen adsorption free energies from DFT, which allows HER trends to be predicted for new systems such as Pd overlayers, the active sites of hydrogenase and nitrogenase, and MoS2 nanoparticles. They maintain that a near-zero hydrogen adsorption free energy is a necessary but not sufficient condition for a good HER catalyst (No̸rskov et al. 2006). Summary: norskov2006.