Preparation and Performance of Nickel-Doped LaSrCoO₃-SrCO₃ Composite Materials for Alkaline Oxygen Evolution in Water...

Perovskites exhibit catalytic properties on the oxygen evolution reaction (OER) in water electrolysis. Elemental doping by specific preparation methods is a good strategy to obtain highly catalytical active perovskite catalysts. In this work, La_0.5Sr_0.5Co_1-xNi_xO_3-δ perovskite materials doped with different ratios of nickel were successfully synthesized by the sol-gel method. The electrochemical measurement results show that for OER in 1 M KOH solution, La_0.5Sr_0.5Co_0.8Ni_0.2O_3-δ prepared by the sol-gel method requires only a low overpotential of 213 mV to reach 10 mA cm^-2, which is significantly lower than that of La_0.5Sr_0.5Co_0.8Ni_0.2O_3-δ prepared by the hydrothermal method for the increasing about 45.24% (389 mV at 10 mA cm^-2). In addition, La_0.5Sr_0.5Co_0.8Ni_0.2O_3-δ by the sol-gel method can be kept stable in an alkaline medium tested for 30 h without degradation. This indicates that the prepared La_0.5Sr_0.5Co_0.8Ni_0.2O_3-δ has better OER performance. The X-ray diffraction (XRD) results show that SrCO₃ is the main phase formed, which is a disadvantage of this method. The performance improvement may be affected by the carbonate phase. The scanning electron microscopy (SEM) results show that layer structured La_0.5Sr_0.5Co_0.8Ni_0.2O_3-δ by the sol-gel method has more surface pores with a pore diameter of about 0.362 μm than spherical granular structured La_0.5Sr_0.5Co_0.8Ni_0.2O_3-δ by the hydrothermal method. X-ray photoelectronic spectroscopy (XPS) results reveal that the crystal lattice of La_0.5Sr_0.5Co_0.8Ni_0.2O_3-δ by nickel doping is lengthened, and the electronic configuration of Co is also changed by the sol-gel preparation process. The improved electrocatalytic performance of La_0.5Sr_0.5Co_0.8Ni_0.2O_3-δ may be attributed to the pore structure formed providing more active sites during the sol-gel process and the improved oxygen mobility with Ni doping by the sol-gel method. The doping strategy using the sol-gel method provides valuable insights for optimizing perovskite catalytic properties.