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 (H₂) evolution via a bimolecular mechanism, providing an opportunity to understand the factors that promote bimetallic H–H coupling. Covalently tethered diiridium catalysts evolve H₂ 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 H₂ 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.

析氢是一种重要的燃料生成反应，一直受到有关单金属和双金属途径作用的机械争论。本研究中的分子铱催化剂通过双分子机制进行光电化学析氢 (H ₂ )，为了解促进双金属 H-H 耦合的因素提供了机会。即使在较低的过电势下，共价束缚的二铱催化剂也比单金属催化剂更快地从中性水中析出H ₂ 。这种改进的出乎意料的起源是非共价超分子自组装成纳米级聚集体，可以有效地收集光并形成 H-H 键。含有长链烷烃取代基的单金属催化剂利用自组装在低过电势下从中性水中析出H ₂，且速率接近该光驱动水分解反应的预期最大值。这项工作提出了用于保持多个催化位点紧密相连并调整催化剂微环境的设计参数。