Addressing electrocatalytic activity of metal-substituted lanthanum manganite for the hydrogen evolution reaction

A comparative electrochemical study between unsubstituted LaMnO3 (LMO) and Ca (LMO-Ca) or Pd (LMO-Pd) substituted LaMnO3, synthesized by the sol-gel method, followed by thermal treatment at low temperature was performed. The obtained materials were studied morpho-structural by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), specific surface (BET), transmission electron microscopy (TEM) and semiquantitative analysis (EDX), and the electrochemical performance was investigated. X-ray diffraction analysis revealed the formation of single-phase compounds with the average crystals size between 18 and 20 nm (calculated from Scherrer equation), crystallized in the cubic structure with Pm-3m space group. The perovskite materials were studied in terms of their electrocatalytic activity for the hydrogen evolution reaction in alkaline medium. Out of the electrodes manufactured using compositions containing the perovskites, the most catalytically active was the one modified from a suspension obtained by adding 2 mg LMO-Pd, 1 mg Carbon Black and 10 mu L Nafion solution in 0.5 mL ethanol, and it displayed an overpotential value of 0.49 V at i = -10 mA/cm2 and a Tafel slope value of 161 mV/dec. The analysis performed in this research work reveals that the most significant results were obtained for the Pd-modified materials.