A Linear Mn3 Molecular Cluster as a Bifunctional Electrocatalyst for Overall Water Splitting

abstract

In this research article, a cluster material [Mn3L2(mu 2-OAc)2] (1) with linear MnII center dot center dot center dot MnII center dot center dot center dot MnII motif in which two peripheral Mn centers are five-coordinated and the central Mn center is six-coordinated has been explored as an excellent OER and HER molecular electrocatalyst (H2L = 2,2 '-(propane-1,3-diylbis(azaneylylidene))bis(ethan-1-yl-1-ylidene)diphenol); (OAc=CH3CO2 -). The organic framework H2L is so flexible, and the preference toward linear assembly is so high, that this cluster is readily accomplished by a synthetic approach that uses H2L and Mn(OAc)2 center dot 4H2O as the building blocks. Characterizations of 1 have been performed by molar conductance, microanalysis, FTIR, UV-vis, FESEM, TGA, PXRD, and SCXRD analyses. The crystal structure of 1 contains two crystallographically equivalent [MnIIL] species interconnected by a central MnII ion via the four mu 2-phenoxide and two mu 2-acetate bridges. Measurement of electrical properties of 1 reveals an interesting current-voltage feature of the aluminum/1 two-terminal device structure. Cluster 1 shows outstanding activity when working as both an OER and HER electrocatalyst, with overpotential values of 324 and 130 mV, respectively, at a current density of 10 mA/cm2. DFT computational studies reveal mechanistic insight into the OER and HER processes, suggesting that the MnII-Ophenoxide-MnII linkage is the active site for the formation of molecular oxygen and hydrogen.

keywords

OXYGEN EVOLUTION; HYDROGEN EVOLUTION; CRYSTAL-STRUCTURE; OXO COMPLEXES; BASE; DINUCLEAR; LIGAND; CONDUCTIVITY; RESOLUTION; REDUCTION

subject category

Chemistry

authors

Barua, M; De, ADT; Sarkar, C; Brandao, P; Dutta, N; Banerjee, A; Kundu, S; Bera, M; Saha, S

Groups

G1 - Porous Materials and Nanosystems

Projects

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

acknowledgements

S.S. greatly acknowledges the financial support received from UGC [Sanction No.: F.38-5/2009 (SR)] and DST [Sanction No.: SR/FT/CS-060/2009], New Delhi. This work is also supported by the infrastructural facilities provided by the Department of Chemistry and Electronic Science, Acharya Prafulla Chandra College under the DST-FIST program (Sanction Order: SR/FST/College-008 date 15/02/2012). A.B. is thankful to Dr. Nirmalendu Sarkar (Principal, Katwa College) for his help to carry out this research work. P.B. gratefully acknowledges the financial support for this work by the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020, and LA/P/006/2020, financed by national funds through the FCT/MCTE (PIDDAC). A.D. wishes to acknowledge DST, New Delhi, for her fellowship (Project No.: CRG/2021/001089). C.S. is thankful to the University of Kalyani for offering the Senior Research Fellowship (SRF) under the University Research Scholarship (URS) program for carrying out the research work. M.B. also acknowledges the University of Kalyani for supporting the Faculty Research Grant (FRG). CSIR-CECRI manuscript number: CECRI/PESVC/Pubs/2025-034.