Work

Geometrical Constraints Weaken a Nickel–Hydrogen Bond and Enable the Homolytic H2 Evolution Mechanism

Year: 2026

Type: preprint

Abstract: Mechanistic studies of the hydrogen evolution reaction (HER) are helping advance catalysis towards energy storage technologies based on water splitting. Homolytic H–H bondforming pathways are one of the fundamental mechanisms of HER, yet well-defined examples of bimetallic coupling in molecular HER catalysts remain extremely rare. A planar tetradentate bipyridine diphosphinite ligand (PONNOP) is reported that constrains the geometry of nickel complexes, weakening the Ni–H bond dissociation free energy and enabling H2 evolution via the homolytic pathway. Crystallography, magnetism, absorption spectroscopy, and computational studies provide insight into the electronic structure enforced by the rigid tetradentate PONNOP ligand, which results in a very weak Ni–H bond in a transiently formed metal hydride. Cyclic voltammetry and chronoamperometry studies are consistent with electrocatalytic HER via the homolytic mechanism. The ability of a tetradentate ligand to induce M–H bond-weakening is discussed as a possible design element in HER by Earth-abundant catalysts.

Source: ChemRxiv

DOI: 10.26434/chemrxiv.15010612/v1

Authors: Grant A. Richter, Quinton J. Bruch, Bethany M. Stratakes, Abhishek Das, Jeremy E. Weber, Carrie L. Donley, Patrick L. Holland, Mehmed Z. Ertem, Alexander J. M. Miller

Institutions: University of North Carolina at Chapel Hill, Yale University, Brookhaven National Laboratory

Language: English

Topic: Electrocatalysts for Energy Conversion

Subfield: Renewable Energy, Sustainability and the Environment

Field: Energy

Domain: Physical Sciences

Open Access status: green

Funders: National Science Foundation, U.S. Department of Energy, Yale University, Office of Science, Division of Chemistry, Basic Energy Sciences

Awards: G1616309272, MRI: Acquisition of a 600 MHz Spectrometer with Cryogenic Probe, G3731664523, G3981648682, G4108146759, G4845723186, G8799472810

OpenAlex ID: W7222518370

Cites: 43

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Related to: 10