MOF-derived Mn/Al sulfide electrocatalysts enabling high faradaic efficiency water oxidation

Abstract

Green hydrogen generation through electrocatalytic water splitting represents a significant tool for harnessing renewable energy. The development of highly stable and efficient noble metal-free dual-functional electrocatalysts is crucial for extensive industrial applications. Herein, initially, a porous bimetallic metal–organic framework (MOF), Mn-MOF@Al-MOF, has been synthesized via a solvothermal method. Subsequently, different MOF derived bimetallic chalcogenides at carbon nanostructures such as MnO@Al₂O₃@C, MnS@Al₂S₃@C, MnSe@Al₂Se₃@C and MnTe@Al₂Te₃@C with suitable chalcogen sources were developed and their electrocatalytic activity was evaluated. Among the derived bimetallic chalcogenides, MnS@Al₂S₃@C outperforms due to the enhanced synergistic interaction between Mn and Al-based composites within the conductive carbon framework, along with the presence of sulfide, which boosts the electrocatalytic performance towards the HER and the OER with minimum overpotentials of 44 and 196 mV, respectively, at a current density of 10 mA cm⁻². Additionally, the practical utilization of MnS@Al₂S₃@C||MnS@Al₂S₃@C for overall water splitting yields a low cell voltage of 1.49 V at a current density of 10 mA cm⁻² with longevity over 100 h and a high faradaic efficiency of ∼100% in a two-electrode configuration in 1.0 M KOH. The activity and stability of the electrocatalyst provide a useful insight into the development of high-efficiency bifunctional electrocatalysts using MOFs.