Direct-grown nebulizer-sprayed nickel-copper mixed metal oxide nanocomposite films as bifunctional electrocatalyst for water splitting

Earth-abundant bifunctional electrocatalysts for water splitting are imperative to realise cost-effective sustainable energy generation. However, selection of suitable materials with apposite properties for the same is highly challenging, not to mention the complicated two or more-step preparation routes with binders and templates involved during synthesis process. Herein, we report for the first time on nickel-copper oxide nanocomposite films as bifunctional electrocatalyst for HER/OER prepared using one-step, binder-free, cost-effective, jet nebulizer spray pyrolysis (JNSP) technique. Synergetic performance of NiO and CuO is investigated by varying Cu concentrations in Cu x Ni 1 − x O mixed oxide system. Structural, morphological and chemical composition of the as-prepared Cu x Ni 1 − x O ( x = 0, 0.1, 0.2 and 0.5) films were investigated from XRD, FESEM, EDS and XPS studies. Point defects such as oxygen and nickel vacancies that promote charge-transfer electronic conductivity favourable for electrochemical reactions were noted from XPS spectra. Variation in optical band gap and Urbach energy with Cu incorporation in NiO is observed from optical studies, whereas change in electrical parameters is noted from four-probe system. When subjected to electrochemical studies using conventional three-electrode setup, as expected, cubic NiO and monoclinic CuO coexisting as nanocomposite in the same matrix exhibited better HER/OER performance when compared to pristine single-phased cubic NiO.