Catalyst self-assembly accelerates bimetallic light-driven electrocatalytic H2 evolution in water

• Published in: Nature chemistry Vol. 16; no. 5; pp. 709 - 716
• Main Authors: Cloward, Isaac N., Liu, Tianfei, Rose, Jamie, Jurado, Tamara, Bonn, Annabell G., Chambers, Matthew B., Pitman, Catherine L., ter Horst, Marc A., Miller, Alexander J. M.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.05.2024; Nature Publishing Group
• Subjects: 639/638/263/406; 639/638/541/966; 639/638/675; 639/638/77/886; 639/638/77/890; Active sites; Aggregates; Alkanes; Analytical Chemistry; Bimetals; Biochemistry; Catalysis; Catalysts; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Design; Design parameters; Evolution; Hydrogen bonds; Hydrogen evolution; Inorganic Chemistry; Iridium; Ligands; Light; Microenvironments; NMR; Nuclear magnetic resonance; Organic Chemistry; Physical Chemistry; Renewable fuels; Self-assembly; Water splitting
• ISSN: 1755-4330; 1755-4349; 1755-4349
• DOI: 10.1038/s41557-024-01483-3

Hydrogen evolution is an important fuel-generating reaction that has been subject to mechanistic debate about the roles of monometallic and bimetallic pathways. The molecular iridium catalysts in this study undergo photoelectrochemical dihydrogen (H 2 ) evolution via a bimolecular mechanism, providing an opportunity to understand the factors that promote bimetallic H–H coupling. Covalently tethered diiridium catalysts evolve H 2 from neutral water faster than monometallic catalysts, even at lower overpotential. The unexpected origin of this improvement is non-covalent supramolecular self-assembly into nanoscale aggregates that efficiently harvest light and form H–H bonds. Monometallic catalysts containing long-chain alkane substituents leverage the self-assembly to evolve H 2 from neutral water at low overpotential and with rates close to the expected maximum for this light-driven water splitting reaction. Design parameters for holding multiple catalytic sites in close proximity and tuning catalyst microenvironments emerge from this work. Although the light-driven generation of hydrogen from water is a promising approach to renewable fuels, the H–H bond formation step represents a persistent mechanistic question. Now light-harvesting molecular catalysts have been shown to self-assemble into nanoscale aggregates that feature improved efficiency for photoelectrochemical H 2 evolution.