TY - JOUR
T1 - A theoretical evaluation of possible transition metal electro-catalysts for N2 reduction
AU - Skulason, Egill
AU - Bligaard, Thomas
AU - Gudmundsdottir, Sigrıdur
AU - Studt, Felix
AU - Rossmeisl, Jan
AU - Abild-Pedersen, Frank
AU - Vegge, Tejs
AU - Jonsson, Hannes
AU - Nørskov, Jens Kehlet
PY - 2012
Y1 - 2012
N2 - Theoretical studies of the possibility of forming ammonia electrochemically at ambient temperature
and pressure are presented. Density functional theory calculations were used in combination with
the computational standard hydrogen electrode to calculate the free energy profile for the reduction
of N2 admolecules and N adatoms on several close-packed and stepped transition metal surfaces in
contact with an acidic electrolyte. Trends in the catalytic activity were calculated for a range of
transition metal surfaces and applied potentials under the assumption that the activation energy
barrier scales with the free energy difference in each elementary step. The most active surfaces,
on top of the volcano diagrams, are Mo, Fe, Rh, and Ru, but hydrogen gas formation will be a
competing reaction reducing the faradaic efficiency for ammonia production. Since the early
transition metal surfaces such as Sc, Y, Ti, and Zr bind N-adatoms more strongly than H-adatoms,
a significant production of ammonia compared with hydrogen gas can be expected on those metal
electrodes when a bias of 1 V to 1.5 V vs. SHE is applied. Defect-free surfaces of the early
transition metals are catalytically more active than their stepped counterparts.
AB - Theoretical studies of the possibility of forming ammonia electrochemically at ambient temperature
and pressure are presented. Density functional theory calculations were used in combination with
the computational standard hydrogen electrode to calculate the free energy profile for the reduction
of N2 admolecules and N adatoms on several close-packed and stepped transition metal surfaces in
contact with an acidic electrolyte. Trends in the catalytic activity were calculated for a range of
transition metal surfaces and applied potentials under the assumption that the activation energy
barrier scales with the free energy difference in each elementary step. The most active surfaces,
on top of the volcano diagrams, are Mo, Fe, Rh, and Ru, but hydrogen gas formation will be a
competing reaction reducing the faradaic efficiency for ammonia production. Since the early
transition metal surfaces such as Sc, Y, Ti, and Zr bind N-adatoms more strongly than H-adatoms,
a significant production of ammonia compared with hydrogen gas can be expected on those metal
electrodes when a bias of 1 V to 1.5 V vs. SHE is applied. Defect-free surfaces of the early
transition metals are catalytically more active than their stepped counterparts.
U2 - 10.1039/c1cp22271f
DO - 10.1039/c1cp22271f
M3 - Journal article
SN - 1463-9076
VL - 14
SP - 1235
EP - 1245
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 3
ER -