Facile synthesis and characterization of SrMnO₃/SrCO₃ nanocomposites by Pechini sol-gel method as efficient and innovated active materials for electrochemical hydrogen storage application

In today's world, the decline of non-renewable energy sources is one of the most critical issues. Due to this fact, most of the research and efforts have been devoted to finding clean and renewable sources of energy as well as energy storage systems. In recent years, hydrogen has attracted the attention of researchers as one of the clean fuels. Among the various methods of storing hydrogen, electrochemical hydrogen storage is exceptionally outstanding. In this work, an attempt has been made to synthesize binary Sr–Mn–O based compounds by using the Pechini sol-gel method, employing different capping and crosslinking agents and varying calcination temperatures, as well as comparing the hydrogen storage activity of pure and impure SrMnO₃. A variety of analysis methods were used to assess the physicochemical characteristics of the samples, including XRD, FE-SEM, EDX, HR-TEM, BET, and FTIR. Chronopotentiometry (ChP) tests at constant current were also conducted on the pure and impure samples to evaluate hydrogen storage efficiency. It was found that the pure perovskites SrMnO₃ (S3) nanostructures are capable of discharging 511.7 mA/g and 896.4 mA/g respectively at initial and 15th discharge cycles in 2.0 M KOH electrolyte solution, respectively, while the discharge capacity of SrMnO3 with impurity SrCO₃ (S1) was 310 mA/g⁻¹ and 950 mA/g⁻¹ under similar conditions at the first and fifteenth discharge cycles. The improvement of electrochemical hydrogen storage behavior for S1 can be attributed to the existence of more electroactive sites in the active materials (working electrode surface), synergistic effects between SrMnO₃ and SrCO₃, as well as the high conductivity of the final sample. The results of this study demonstrate that these synthesized materials are able to be applied in hydrogen storage applications. A mechanism that has also been proposed is that hydrogen is stored through physisorption as well as redox reaction.