Deciphering Electrocatalytic Hydrogen Production in Water Through a Bioinspired Water-Stable Copper(II) Complex Adorned with (N2S2)-Donor Sites

Abstract

Electrocatalytic hydrogen production stands as a pivotal cornerstone in ushering the revolutionary era of the hydrogen economy. With a keen focus on emulating the significance of hydrogenase-like active sites in sustainable H₂ generation, a meticulously designed and water-stable copper(II) complex, [Cl−Cu−L^N2S2]ClO₄, featuring the N,S-type ligand, L^N2S2 (2,2′-((butane-2,3-diylbis(sulfanediyl))bis(methylene))dipyridine), has been crafted and assessed for its prowess in electrocatalytic H₂ production in water, leveraging acetic acid as a proton source. The molecular catalyst, adopting a square pyramidal coordination geometry, undergoes -Cl substitution by H₂O during electrochemical conditions yielding [H₂O−Cu−L^N2S2]²⁺ as the true catalyst, showcases outstanding activity in electrochemical proton reduction in acidic water, achieving an impressive rate of 241.75 s⁻¹ for hydrogen generation. Controlled potential electrolysis at −1.2 V vs. Ag/AgCl for 1.6 h reveals a high turnover number of 73.06 with a commendable Faradic efficiency of 94.2 %. A comprehensive analysis encompassing electrochemical, spectroscopic, and analytical methods reveals an insignificant degradation of the molecular catalyst. However, the post-CPE electrocatalyst, present in the solution domain, signifies the coveted stability and effective activity under the specified electrochemical conditions. The synergy of electrochemical, spectroscopic, and computational studies endorses the proton-electron coupling mediated catalytic pathways, affirming the viability of sustainable hydrogen production.