Developing efficient catalysts for electrolysis, in particular for the oxygen evolution in the anodic half cell reaction, is an important challenge in energy conversion technologies. By taking inspiration from the catalytic properties of single-atom catalysts and metallo-proteins, we exploit the potential of metal-organic networks as electrocatalysts in the oxygen evolution reaction (OER). A dramatic enhancement of the catalytic activity toward the production of oxygen by nearly 2 orders of magnitude is demonstrated for novel heterobimetallic organic catalysts compared to metallo-porphyrins. Using a supramolecular approach we deliberately place single iron and cobalt atoms in either of two different coordination environments and observe a highly nonlinear increase in the catalytic activity depending on the coordination spheres of Fe and Co. Catalysis sets in at about 300 mV overpotential with high turnover frequencies that outperform other metal-organic catalysts like the prototypical hangman porphyrins.

Electrochemical conversions at fuel cell electrodes are complex processes. In particular, the oxygen reduction reaction has substantial overpotential limiting the electrical power output efficiency. Effective and inexpensive catalytic interfaces are therefore essential for increased performance. Taking inspiration from enzymes, earth-abundant metal centres embedded in organic environments present remarkable catalytic active sites. Here we show that these enzyme-inspired centres can be effectively mimicked in two-dimensional metal-organic coordination networks self-assembled on electrode surfaces. Networks consisting of trimesic acid and bis-pyridyl-bispyrimidine coordinating to single iron and manganese atoms on Au(111) effectively catalyse the oxygen reduction and reveal distinctive catalytic activity in alkaline media. These results demonstrate the potential of surface-engineered metal-organic networks for electrocatalytic conversions. Specifically designed coordination complexes at surfaces inspired by enzyme cofactors represent a new class of nanocatalysts with promising applications in electrocatalysis.

Understanding catalyst stability requires real-space insight on the molecular level and complementary spectroscopic characterisation.

Metal-organic coordination networks self-assembled on surfaces have emerged as functional low-dimensional architectures with potential applications ranging from the fabrication of functional nanodevices to electrocatalysis. Among them, bis-pyridyl-bispyrimidine (PBP) and Fe-PBP on noble metal surfaces appear as interesting systems in revealing the details of the molecular self-assembly and the effect of metal incorporation on the organic network arrangement. Herein, we report a combined STM, XPS, and DFT study revealing polymorphism in bis-pyridyl-bispyrimidine adsorbed adlayers on the reconstructed Au(111) surface. The polymorphic structures are converted by the addition of Fe adatoms into one unique Fe-PBP surface structure. DFT calculations show that while all PBP phases exhibit a similar thermodynamic stability, metal incorporation selects the PBP structure that maximizes the number of metal-N close contacts. Charge transfer from the Fe adatoms to the Au substrate and N-Fe interactions stabilize the Fe-PBP adlayer. The increased thermodynamic stability of the metal-stabilized structure leads to its sole expression on the surface.