Issue 33, 2024

Decrypting the hydrogen evolution in alkaline water with novel magnetoactive cobalt(ii) complex-driven cobalt oxide electrocatalysts

Abstract

Under the gravity of future socio-economic development, the viability of water electrolysis still hinges on the accessibility of stable earth-abundant electrocatalysts and net energy efficiency. This work emphasizes the design and synthesis of two newly developed cobalt(II) complexes, [Co(HL)2(NCS)2] (Comono) and [Co2(L)3(CH3OH)]ClO4 (Codi), with a (N,O)-donor ligand, HL (2-methoxy-6-(((2-methoxyphenyl)imino)methyl)phenol). The study delves into understanding their structural, morphological, magnetic, and charge transport characteristics. Moreover, the study explores the potential of these complexes in catalyzing hydrogen production through heterogeneous electrocatalysis. The X-ray crystal structure of Comono reveals the octahedral geometry of the Co(II) ion, adopting two HL units and two NCS units. The Codi complex exhibits a doubly-phenoxo-O-bridged (μ1,1) dinuclear complex, forming a typical octahedral geometry for both the Co(II) centres in coupling with three units of L. Temperature-dependent magnetic susceptibility measurements showed that all of the Co(II) ion in Comono shows a typical paramagnetic behaviour for high spin octahedral Co(II) ions while the Co(II) centres in Codi are coupled with doubly-phenoxo-bridges bearing weak ferromagnetic characteristics at low temperature. Electron transport properties of the Co(II) complex-mediated Schottky device address the superior carrier mobility (μ) for Codi (9.21 × 10−5) over Comono (2.02 × 10−5 m2 v−1 s−1) with respective transit times of 1.70 × 10−9 and 7.77 × 10−9 s. Additionally, electron impedance spectral analysis supports the lower electrical transport resistance of Codi relative to Comono. The heterogeneous electrocatalytic HER activity of Codi and Comono in 0.1 M KOH shows excellent electrocatalytic efficiency in terms of the various electrochemical parameters. Constant potential electrolysis, multi-cycle CVs, and post-HER analysis reveal the pre-catalytic nature of the complexes, which in turn delivers Co3O4 nanoparticles as the active catalysts for efficient hydrogen evolution.

Graphical abstract: Decrypting the hydrogen evolution in alkaline water with novel magnetoactive cobalt(ii) complex-driven cobalt oxide electrocatalysts

Supplementary files

Article information

Article type
Paper
Submitted
08 May 2024
Accepted
23 Jul 2024
First published
24 Jul 2024

Dalton Trans., 2024,53, 13805-13814

Decrypting the hydrogen evolution in alkaline water with novel magnetoactive cobalt(II) complex-driven cobalt oxide electrocatalysts

S. Saha, N. Diyali, S. Diyali, S. J. Panda, M. Das, S. Acharya, P. K. Mudi, M. Singh, P. P. Ray, C. S. Purohit and B. Biswas, Dalton Trans., 2024, 53, 13805 DOI: 10.1039/D4DT01358A

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