Electrochemical splitting of water has been considered to be a very promising technology for a sustainable hydrogen economy. However, the efficiency of water electrolysis is limited by the oxygen evolution reaction (OER) due to kinetics, which results in a large anodic overpotential.[1]

Therefore, the development and optimization of new catalysts for the OER is of great importance in overcoming the challenges in energy conversion.[2]

The theoretical overpotentials of different metal oxides in oxygen evolution reaction based processes can be predicted by DFT calculations. The well-known volcano plot locates the oxides of Ru and Ir near the top. Recently it was reported[3], that the volcano type limitation can be removed by an active site modification for instance by the introduction of cobalt or nickel. However, ruthenium based electrocatalysts exhibit a very low stability during OER, whereas iridium is considered as the best compromise between an active and stable electrocatalyst.[2]

Here, the reported approach in [3] is extended to iridium based systems. The Ni underpotential deposition (UPD) on Ir(111) was performed in phosphate buffer (pH = 6.84) with 2 mM NiSO₄ at 0.0 V vs. RHE for 10 minutes, under which the (111) surface should be completely covered with a Ni species. By annealing the Ni/Ir(111) monolayer for 2 minutes at 400 °C in H₂/Ar (5 % H₂ in Ar) a near surface alloy (NSA) was obtained. A subsequent heat treatment of the Ni/Ir(111) NSA for 2 minutes at 400 °C in CO/Ar (1 % CO in Ar) was conducted, to form a surface alloy (SA) of Ni and Ir on the surface. The thermal restructuring of the surfaces were all performed within an inductive electrochemical single crystal cell.[4] The obtained surfaces are characterized using ICP‑MS and LEIS. Furthermore, the catalytic activity of the different surfaces towards oxygen evolution reaction is compared. Herein, we present an approach to tailor the binding energy of Ir towards reaction intermediates in the OER.

[1] Y. Surendranath, M. W. Kanan, D. G. Nocera, J. Am. Chem. Soc. 132, 16501 (2010).

[2] M. Carmo, D. L. Fritz, J. Mergel, D. Stolten, International Journal of Hydrogen Energy 38, 4901 (2013).

[3] N. B. Haclk, V. Petrykin, P. Krtil, J. Rossmeisl, Phys. Chem. Chem. Phys. 16, 13682 (2014)[4] A. S. Bondarenko, I. E. L. Stephens, I. Chorkendorff, Electrochemistry Communications 23, 33 (2012).