Steps towards highly-efficient water splitting and oxygen reduction using nanostructured ß-Ni(OH)2.

ABSTRACT

ß-Ni(OH)2 nanoplatelets are prepared by a hydrothermal procedure and characterized by scanning and transmission electron microscopy, X-ray diffraction analysis, Raman spectroscopy, and X-ray photoelectron spectroscopy. The material is demonstrated to be an efficient electrocatalyst for oxygen reduction, oxygen evolution, and hydrogen evolution reactions in alkaline media. ß-Ni(OH)2 shows an overpotential of 498 mV to reach 10 mA cm-2 towards oxygen evolution, with a Tafel slope of 149 mV dec-1 (decreasing to 99 mV dec-1 at 75 °C), along with superior stability as evidenced by chronoamperometric measurements. Similarly, a low overpotential of -333 mV to reach 10 mA cm-2 (decreasing to only -65 mV at 75 °C) toward hydrogen evolution with a Tafel slope of -230 mV dec-1 is observed. Finally, ß-Ni(OH)2 exhibits a noteworthy performance for the ORR, as evidenced by a low Tafel slope of -78 mV dec-1 and a number of exchanged electrons of 4.01 (indicating direct 4e--oxygen reduction), whereas there are only a few previous reports on modest ORR activity of pure Ni(OH)2.