Formation of a Ni(OH)2/NiOOH active redox couple on nickel nanowires for formaldehyde detection in alkaline media

• Published in: Electrochimica acta Vol. 309; pp. 346 - 353
• Main Authors: Trafela, Špela, Zavašnik, Janez, Šturm, Sašo, Rožman, Kristina Žužek
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 20-06-2019; Elsevier BV
• Subjects: Amorphous; Electro-catalytic oxidation; Electrodes; Formaldehyde; Formaldehyde oxidation; Nanowires; Ni nanowires; Nickel compounds; Nickel hydroxides; Noble metals; Oxidation; Reproducibility; Selectivity; Surface layers; Transformations; Work functions; Electro-catalytic oxidation; Formaldehyde oxidation; Amorphous; Nickel hydroxides; Ni nanowires
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2019.04.060

Highly ordered, Ni(OH)2Ni-nanowire-based receptor elements were electrochemically fabricated and tested for formaldehyde (HCHO) detection by monitoring their oxidation ability in alkaline media. In order to normalize the electrochemical output currents, the Ni nanowires' electrochemically active surface area was assessed using an oxalate-based method after the template was released. The electrochemical transformation of the Ni-nanowire surfaces to a Ni(OH)2/NiOOH redox couple was performed in 0.5-mol L−1 KOH using cyclic voltammetry at 200 mV s−1. The transformation was monitored for two cases: without KOH modification and with KOH-modified Ni nanowires. It was shown that the non-modified Ni nanowires possess a poor electrochemical response to HCHO oxidation, mainly due to the formation of a NiO surface layer. On the other hand, the modified Ni nanowires donated an electron to the HCHO oxidation reaction, resulting in high output-current densities, attributed to the thin Ni(OH)2/NiOOH layer, its amorphous state (TEM/SAED) and its small work function, due to electron doping from under the layered Ni. The modified Ni-nanowire-based electrodes had high sensitivity, reproducibility, selectivity and a low detection limit (0.8 μmol L−1). The developed HCHO Ni-nanowire-based electrodes’ characteristics surpass other Ni-based nanostructured electrodes and have limits of detection comparable to those achieved with noble metals.