K+-driven interfacial water reconstruction via charge-enriched heterointerfaces for accelerated alkaline hydrogen evolution

Cu single atoms regulate crystalline-amorphous RuO x interfaces • K⁺ enrichment reconstructs interfacial water structure • Accelerated Volmer step via improved proton availability • High HER activity with low overpotential and small Tafel slope • Long-term stability demonstrated in practical AEM electrolyzer The sluggish water dissociation kinetics in alkaline media remains a major bottleneck for efficient hydrogen evolution reaction (HER). Beyond intrinsic active sites, the interfacial microenvironment, particularly local charge distribution and water structure, plays a decisive role in governing reaction pathways. Herein, we report a two-dimensional Cu-modified RuO x catalyst containing carbonaceous components (denoted as Cu-RuO x /C), featuring crystalline-amorphous heterointerfaces that create charge-enriched interfacial regions for regulating the interfacial water network. Cu incorporation generates a charge-enriched surface that promotes the accumulation of K + near the catalyst interface, thereby reconstructing the interfacial hydrogen-bond network. This regulation shortens the K + -surface distance and weakens hydrogen-bond connectivity within interfacial water, leading to a decreased fraction of tetracoordinate hydrogen-bonded water and an increased proportion of free water. Such an optimized interfacial water structure ensures sufficient proton supply during the HER process. As a result, Cu-RuO x /C delivers an ultralow overpotential of 13 mV at 10 mA cm −2 in 1 M KOH and sustains 800 h of operation at 1000 mA cm −2 in an anion exchange membrane water electrolyzer. This work demonstrates highly dispersed Cu modulation as an effective strategy for engineering catalytic microenvironments to enhance alkaline HER. Download: Download high-res image (151KB) Download: Download full-size image Charge-enriched Cu-RuO x heterointerfaces induce K + -driven water reconstruction, accelerating water dissociation and HER kinetics while delivering ultralow overpotential and outstanding durability.