Electrocatalytic Properties of Ni-Doped BaFe12O19 for Oxygen Evolution in Alkaline Solution

Transition metal oxide (TMO) continues to be studied and developed as an oxygen evolution reaction (OER) electrocatalyst due to its abundance and low price. The aim of this experiment was to evaluate Ni2+-doped BaFe12O19 (BHF) as an OER electrocatalyst in an alkaline medium. BHF and Ni-doped BHF was synthesized through a low temperature coprecipitation technique followed by a calcination process at 750oC for 4 h. Diffractograms of the BHF and the Ni-doped BHF indicated a single phase on the synthesized BHF and formed Fe2O3 impurities on the Ni-doped BHF. SEM images showed a homogenous plate-shaped particles in the BHF, while the Ni-doped BHF had larger inhomogeneous particles. Ni dopant increased OER electrocatalytic activity of BHF based on overpotential on specific current density. The Ni-doped BHF had comparable activity to some metallic oxides based on their overpotential values at specific current density value.

Triple Layer Tungsten Trioxide, Graphene, and Polyaniline Composite Films for Combined Energy Storage and Electrochromic Applications

Different polyaniline (PANI)-based hybrid films were successfully prepared by electro-polymerizing aniline monomers onto pre-spin-coated indium tin oxide (ITO) glass slides with WO₃, graphene, or WO₃/graphene films. Comparing with pristine PANI, the shifts of the characteristic peaks of PANI-based nanocomposites in UV-visible absorption spectra (UV-vis) and Fourier transform infrared spectroscopy (FT-IR) indicate the chemical interaction between the PANI matrix and the nanofillers, which is also confirmed by the scanning electron microscope (SEM) images. Corresponding coloration efficiencies were obtained for the WO₃/PANI (40.42 cm² C^-1), graphene/PANI (78.64 cm² C^-1), and WO₃/graphene/PANI (67.47 cm² C^-1) films, higher than that of the pristine PANI film (29.4 cm² C^-1), suggesting positive effects of the introduced nanofillers on the electrochromic performance. The areal capacitances of the films were observed to increase following the order as bare WO₃ < WO₃/graphene < pristine PANI < WO₃/PANI < graphene/PANI < WO₃/graphene/PANI films from both the cyclic voltammogram (CV) and galvanostatic charge-discharge (GCD) results. The enhanced energy storage and electrochromic performances of the PANI-based nanocomposite films can be attributed to the capacitance contributions of the introduced nanofillers, increased PANI amount, and the rougher morphology due to the embedment of the nanofillers into the PANI matrix. This extraordinary energy storage and electrochromic performances of the WO₃/graphene/PANI film make it a promising candidate for combined electrochromic and energy storage applications.