The production of molecular hydrogen from water electrolysis is a challenging issue mainly because of the sluggish kinetics of the oxygen evolution reaction (OER) and the low catalyst stability[1]. For alkaline electrolyzers, nickel hydroxides have been attracting attention due to their high activity for this reaction[2]. In this work, we have synthesized and characterized nickel hydroxide nanoparticles showing enhanced activity for the oxygen evolution reaction when compared to the state-of-art iridium oxide. This is probably due to its amorphous characteristic and the preferential formation of α-phase, confirmed by X-ray diffraction pattern and the cyclic voltammetric profile that presents a redox pair in the range of potential corresponding to the alpha phase (from -0.25 V to 0.45 V vs. normal hydrogen electrode)[3]. The effects of electrolyte composition, comprazing LiOH, NaOH and KOH, were also studied for the nickel hydroxides catalysts in comparison to gold electrode. The results have shown that the configuration of the active sites and thus the kinetics of the OER depend on the interaction between the species in the electrolyte and the catalyst surface.

Acknowledgements: N.P. and E.T. acknowledge São Paulo Foundation (FAPESP) for financial support (grants No. 2015/18274-5 and 2013/16930-7)

References

[1] M.W. Kanan, D.G. Nocera, In situ formation of an oxygen-evolving catalyst in neutral water containing phosphate and Co2+., Science. 321 (2008) 1072–1075.

[2] O. Diaz-Morales, D. Ferrus-Suspedra, M.T.M. Koper, The importance of nickel oxyhydroxide deprotonation on its activity towards electrochemical water oxidation, Chem. Sci. 7 (2016) 2639–2645.

[3] J. Van Drunen, A.F.B. Barbosa, G. Tremiliosi-filho, The Formation of Surface Oxides on Nickel in Oxalate-Containing Alkaline Media, (2015) 481–491.