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Heteroatom doping has emerged as a highly effective strategy to enhance the activity of metal‐based electrocatalysts toward the oxygen evolution reaction (OER). It is widely accepted that the doping does not switch the OER mechanism from the adsorbate evolution mechanism (AEM) to the lattice‐oxygen‐mediated mechanism (LOM), and the enhanced activity is attributed to the optimized binding energies toward oxygen intermediates. However, this seems inconsistent with the fact that the overpotential of doped OER electrocatalysts (<300 mV) is considerably smaller than the limit of AEM (>370 mV). To determine the origin of this inconsistency, we select phosphorus (P)‐doped nickel‐iron mixed oxides as the model electrocatalysts and observe that the doping enhances the covalency of the metal‐oxygen bonds to drive the OER pathway transition from the AEM to the LOM, thereby breaking the adsorption linear relation between *OH and *OOH in the AEM. Consequently, the obtained P‐doped oxides display a small overpotential of 237 mV at 10 mA cm−2. Beyond P, the similar pathway transition is also observed on the sulfur doping. These findings offer new insights into the substantially enhanced OER activity originating from heteroatom doping. [ABSTRACT FROM AUTHOR]

Subnanometric metal clusters usually have unique electronic structures and may display electrocatalytic performance distinctive from single atoms (SAs) and larger nanoparticles (NPs). However, the electrocatalytic performance of clusters, especially the size-activity relationship at the sub-nanoscale, is largely unexplored. Here, we synthesize a series of Ru nanocrystals from single atoms, subnanometric clusters to larger nanoparticles, aiming at investigating the size-dependent activity of hydrogen evolution in alkaline media. It is found that the d band center of Ru downshifts in a nearly linear relationship with the increase of diameter, and the subnanometric Ru clusters with d band center closer to Femi level display a stronger water dissociation ability and thus superior hydrogen evolution activity than SAs and larger nanoparticles. Benefiting from the high metal utilization and strong water dissociation ability, the Ru clusters manifest an ultrahigh turnover frequency of 43.3 s−1 at the overpotential of 100 mV, 36.1-fold larger than the commercial Pt/C. Metal nanocluster properties undergo drastic activity alterations with slight size variations, although in-depth examinations of such changes are challenging to perform. Here, authors demonstrate Ru cluster size governs the d-band center position and electrocatalytic activity for H2 evolution. [ABSTRACT FROM AUTHOR]

• A nature-inspired etching strategy is developed for the construction of karst topography (KT)-featured electrode. • The KT architecture offers a "superaerophobic" surface for rapidly releasing O 2 bubbles during electrocatalysis. • Experimentally identifying that the core-shell structure optimizes the adsorption strength of *OH intermediates. • The obtained electrocatalysts achieve the large current densities of 1500 mA cm−2 at an overpotential of 380 mV. Exploring of electrocatalysts for high-output oxygen evolution reaction (OER) is key to practical applications, but still remains challenging. Here, we developed a nature-inspired etching strategy for the construction of karst topography (KT)-featured electrode comprising core-shell structured Ni(0)@Ni(II) towards efficient OER. Intriguingly, the KT architecture confers a "superaerophobic" surface to render the large amount of generated O 2 bubbles release rapidly and timely from the electrode surface at the high current density of OER (i.e., 1500 mA cm−2). Moreover, this strategy allows good control over the generated core-shell structure for promoting the heterointerface synergetic effect of Ni(0)@Ni(II). By adding probing molecules to react with OER intermediates under operation conditions, we obtain first direct experimental evidence that the core-shell structure can optimize the adsorption strength of *OH for significantly boosting the OER kinetics. Notably, the obtained electrode has excellent performance for OER with a small overpotenital of 380 mV at 1500 mA cm−2. [ABSTRACT FROM AUTHOR]