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Strengthening OH adsorption on electrocatalyst is crucial to promote the rate‐determining water dissociation step of alkaline hydrogen evolution reaction (HER), whereas too‐intensified OH adsorption will poison the active sites instead. This dilemma remains one of the major challenges for improving the electrocatalysts' alkaline HER activities. Herein, a surprising finding that the strongly adsorbed OH on an ultrafine quinary PtCoCuNiZn nanoalloy can be facilely desorbed via a unique gradient OH desorption pattern is reported, which tremendously boosts its alkaline HER activity. Theoretical simulations unravel that the ultrafine PtCoCuNiZn nanoalloy possesses versatile metal sites for adsorbing OH and the strongly adsorbed OH can be gradiently transferred to desorb from the ultrafine PtCoCuNiZn nanoalloy with moderate energy barriers for each transfer step that is the gradient OH desorption. In the meanwhile, the unique gradient OH desorption mode on the ultrafine PtCoCuNiZn nanoalloy is also experimentally evidenced by the in situ Raman spectroscopy and cyclic voltammetry measurements. This finding offers a fresh opportunity to expedite the alkaline HER without compromising the OH adsorption strength on electrocatalysts, which thus maximally promotes their water dissociation properties and unlocks the full potential of their alkaline HER activities. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of CO 2 to multi-carbon products is very attractive yet particularly challenging due to the low efficiency of C-C coupling over currently used electrocatalysts. In this work, we report a dual-atom catalyst (Cu 2 /NC) capable of selectively promoting electro-reduction of CO 2 to C 2 H 4. The Faradaic efficiency of CO 2 -to-C 2 H 4 over the Cu 2 /NC is up to ∼34.9% with a current density of 33.6 mA·cm−2. By contrast, its Cu single-atom counterpart only generates CO without forming C 2 H 4. The density functional theory (DFT) calculations reveal that the Cu-Cu sites largely promote the adsorption of *CO and reduce the energy barrier of C-C coupling between the adsorbed *CO relative to that of the single Cu sites, which accounts for the high C 2 H 4 selectivity of the Cu 2 /NC. [Display omitted] • Highly efficient Cu dual-atom catalysts were prepared to catalyze CO2RR. • Compared with Cu single-atom catalyst, dual-atom catalyst was more favorable to reduce CO2 to multi-carbon product C2H4. • DFT calculations revealed that the energy barrier of C-C coupling was largely reduced on the dual Cu catalysts. [ABSTRACT FROM AUTHOR]