Surface-induced a local electronegative field to engineer k-enriched microenvironment for high-performance alkaline hydrogen evolution reaction

The CeO2 surface induced local electronegative microenvironment under alkaline condition facilitates the adsorption and enrichment of K cations on Ru clusters, thereby reducing the energy barrier of water dissociation and improving the alkaline HER performance. [Display omitted] •The surface-induced strategy is proposed to regulate reaction microenvironment.•The as-constructed local electronegative field promotes in-situ enrichment of K cations from KOH electrolyte.•A hydrated K cations mediated HER enhancement mechanism is verified by experiment and DFT calculations.•The as-synthesized electrocatalyst exhibits excellent prospects in alkaline seawater HER. The design and development of the superior alkaline hydrogen evolution reaction (HER) electrocatalysts via tuning reaction microenvironment is an efficient but challenging approach. In this work, we proposed a surface-induced strategy for intentionally engineering a local electric field to in-situ enrich the active species. Specifically, Ru-CeO2@C electrocatalyst with Ru clusters embedded in CeO2@C matrix was synthesized by the pyrolysis of Ru/Ce-MOFs composite. The surface charge modulation of CeO2 resulted in an electronegative environment for Ru clusters supported on its surface, thus abundantly enriching K cations from KOH electrolyte. The as-prepared Ru-CeO2@C exhibited excellent HER activity and superior stability in alkaline condition. Moreover, this electrocatalyst can fully utilize the excess alkali-metal ions and inhibit the influence to active components by Cl anions in alkaline seawater HER. In a alkaline seawater electrolyte with 1 M KOH and 3 M KCl, it only required a low overpotential of 13 mV to obtain 10 mA cm−2 current density, with a Tafel slope of 24 mV dec−1. Theoretical calculation results also indicated that the energy barrier of water dissociation as rate-determining step on Ru surface is greatly reduced derived from the mediation of hydrated K cations.