Abstract
Doping is promising strategy for the alteration of nanomaterials to enhance their optical, electrical, and catalytic activities. The development of electrocatalysts for oxygen reduction reactions (ORR) with excellent activity, low cost and durability is essential for the large-scale utilization of energy storage devices such as batteries. In this study, MnO2 and Ni-doped MnO2 nanowires were prepared through a simple co-perception technique. The influence of nickel concentration on electrochemical performance was studied using linear sweep voltammetry and cyclic voltammetry. The morphological, thermal, structural, and optical properties of MnO2 and Ni-doped MnO2 nanowires were examined by SEM, ICP-OES, FT-IR, XRD, UV–Vis, BET and TGA/DTA. Morphological analyses showed that pure MnO2 and Ni-doped MnO2 had flower-like and nanowire structures, respectively. The XRD study confirmed the phase transformation from ε to α and β phases of MnO2 due to the dopant. It was also noted from the XRD studies that the crystallite sizes of pure MnO2 and Ni-doped MnO2 were in the range of 2.25–6.6 nm. The band gaps of MnO2 and 0.125 M Ni-doped MnO2 nanoparticles were estimated to be 2.78 and 1.74 eV, correspondingly, which can be seen from UV–Vis. FTIR spectroscopy was used to determine the presence of functional groups and M–O bonds (M = Mn, Ni). The TGA/TDA examination showed that Ni-doping in MnO2 led to an improvement in its thermal properties. The cyclic voltammetry results exhibited that Ni-doped MnO2 nanowires have remarkable catalytic performance for ORR in 0.1 M KOH alkaline conditions. This work contributes to the facile preparation of highly active and durable catalysts with improved catalytic performance mainly due to the predominance of nickel.Article HighlightsMnO2 and Ni-doped MnO2 nanowires were synthesized via a facile co-perception approach.Nickel doping in MnO2 induces the formation of wire-like nanostructures.Nickel doping enhances the electrochemical activity and thermal stability of MnO2 nanoflowers.The addition of nickel into MnO2 promoted the catalytic activity for oxygen reduction reaction.A higher catalytic activity was achieved in 0.125 M Ni-MnO2 nanowires.Graphic abstract
Highlights
The focus on low-carbon emissions and the concept of sustainability has notably proposed the development of sustainable energy sources [1, 2]
Electrochemical energy storage tools such as metal-air batteries (MABs) and fuel cells are considered to play a significant impact in the transformation to a sustainable prospect [3,4,5]
One of the main problems that restrict the application of lithium-ion batteries for electric vehicles is its low specific energy density [6, 7]
Summary
The focus on low-carbon emissions and the concept of sustainability has notably proposed the development of sustainable energy sources [1, 2]. The ORR is a vital cathodic reaction in fuel cells and MABs [16, 17] Precious metals such as Platinum (Pt) and Pt-based alloys are the most effective ORR electrode substances [18, 19]. The application of Pt and its derivatives as ORR catalysts is limited because of their poor stability, limited access, and high price [20, 21] To address these concerns, strategies have been designed to prepare highly-active, durable, and more stable non-precious metal-based ORR catalysts [22, 23]. Among transition metal oxides, MnO2 can be used as an air electrocatalyst for the ORR due to its excellent catalytic performance, abundance, low price, and environmental safety [26,27,28]. For enhanced ORR catalyst activity, different metals have been doped
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