The electrochemical oxygen evolution reaction (OER) is a half-reaction of water-splitting for hydrogen generation, yet suffers from its sluggish kinetics and large overpotential. It is highly desirable to develop efficient and stable OER electrocatalysts for the advancement of water-splitting. Herein, by means of density functional theory (DFT) calculations, we systematically investigated a series of two-dimensional (2D) dual-atom catalysts (DACs) on a novel synthesized covalent organic framework (COF) material as potential efficient catalysts toward the OER. The designed 6 homonuclear (2TM-COF) and 15 heteronuclear (TM₁TM₂-COF) DACs all exhibit good stability. There is a strong scaling relationship between the adsorption Gibbs free energies of HO* and HOO* intermediates, and the OER overpotential (η^OER) volcano curve can be plotted as a function of ΔG_O* − ΔG_HO*. RhIr-COF shows the best OER catalytic activity with a η^OER value of 0.29 V, followed by CoNi-COF (0.33 V), RuRh-COF (0.34 V), and NiIr-COF (0.37 V). These four OER DACs exhibit lower onset potential and higher current density than that of the IrO₂(110) benchmark catalyst. Aided by the descriptor identification study, the Bader charge that correlated with the Pauling electronegativity of the embedded dual-metal atoms was found to be the most important factor governing the catalytic activity of the OER. Our work highlights a potentially efficient class of 2D COF-based DACs toward the OER.

Unraveling the substrate adsorption structure–performance relationship is pivotal for heterogeneous carbon supported metal single-atom catalysts (M₁/C SACs). However, due to the complexity of the functional groups on carbon material surface, it is still a great challenge. Herein, inspired by structure of enzymes, we used activated carbon (AC), which has adjustable surface oxygen functional groups (OFGs), supported atomically dispersed Fe-N₄ sites as heme-like catalyst. And based on a combination of scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), Mössbauer spectroscopy, Fourier transform infrared (FT-IR) characterizations, kinetics experiments and density functional theory (DFT) calculations, we revealed the effect of substrate adsorption behavior on AC support surface, that is, with the increase of carboxyl group in OFGs, the adsorbed 3,3',5,5'-tetramethylbenzidine (TMB) molecular increased, and consequently the substrate enriched on AC surface. Such carboxyl group as well as Fe-N₄ active sites synergistically realized high-efficiency peroxidase-like activity, just like the heme. This work suggests that simultaneously constructing metal single-atom active sites and specific functional groups on carbon support surface may open an avenue for engineering metal-support synergistic catalysis in M₁/C SACs, which can further improve catalytic performance.

A single water molecule is nothing special. However, macroscopic water displays many anomalous properties at interfaces, such as hydrophobicity and hydrophilicity. Although the underlying mechanisms remain elusive, hydrogen bonds between water molecules are expected to play a major role in these interesting phenomena. An important question concerns whether water clusters containing few molecules are qualitatively different from a single molecule. Using the water adsorption behavior as an example and by carefully choosing two-dimensional silicene as the substrate material, we demonstrate that water monomers, dimers, and trimers show distinct adsorption properties at the substrate surface. On silicene, the additional water molecules in dimers and trimers induce a transition from physisorption to chemisorption and then to dissociation, arising from the enhancement of charge transfer and proton transfer processes induced by hydrogen bonding. Such a hydrogen bond autocatalytic effect is expected to have broad applications in metal-free catalysis for the oxygen reduction reaction and water dissociation.