ABSTRACT Conventional non‐noble hydrogen evolution reaction catalysts are plagued by excessive hydrogen adsorption and instability. To overcome this, we pioneer a high‐entropy single‐atom (HESA) catalyst via precise anchoring of multiple transition metals on carbon supports. The HESA catalyst achieves record‐breaking alkaline HER performance of 44 mV@10 mA cm −2 (matching commercial Pt/C catalyst) and 300 h stability, resolving the persistent activity‐stability trade‐off. Systematical characterizations reveal that low‐coordination metal sites induce significant metal‐support charge redistribution. Electronegative supports withdraw electrons from metal centers, while π‐back‐donation downshifts metal d‐band centers, optimizing the Gibbs free energy of intermediate H atoms (ΔG H* ). Atomic‐scale imaging further confirms uniform charge distribution and Ångström‐level electric field response. Crucially, adjacent multi‐metal sites synergistically lower energy barriers for both water dissociation and hydrogen desorption through a synergistic electronic buffering effect. This work establishes entropy‐driven microenvironment engineering as a paradigm for cooperative optimization of active sites and electronic structures, opening avenues for durable non‐precious catalysts.

ABSTRACT In this work, we demonstrate the integration of a flat liquid jet sample delivery system into a compact soft x‐ray absorption spectrometer using a table‐top laser‐induced plasma source. A high‐speed flat liquid sheet is formed by the collision of two cylindrical jets. This micrometer‐thin lamella can ideally be utilized for transmission‐mode soft x‐ray absorption spectroscopy using krypton plasma emission. Detailed analysis of the jet's thickness profile is achieved applying Lambert–Beer's law. Measurements on water, focusing on the oxygen K‐edge, reveal a lamella thickness profile ranging from 500 nm to 1 μm over a length of 3.8 mm. Additionally, we have investigated aqueous solutions of iron salts, capturing near edge x‐ray absorption fine structure spectra over a broad spectral range from the nitrogen K‐edge to the iron L‐edge. Focused analysis on iron species in aqueous solutions enabled us to distinguish quantitatively between the oxidation states of Fe 2+ and Fe 3+ at the iron L‐edge. Our results are compared with measurements obtained under similar conditions at a synchrotron.

Abstract Despite two‐dimensional (2D) conductive metal–organic frameworks (cMOFs) being attractive due to their intrinsic electrical conductivity and redox activity for energy applications, alleviating the constrained mass transfer within long‐range micropore channels remains a significant challenge. Herein, we present a tandem assembly and etching chemistry, to incorporate perpendicularly aligned mesopores into the micropores of cMOFs, via a bi‐functional modulator. Synchrotron spectral and morphological analyses demonstrate that the elaborate ammonia modulator first coordinates with Zn 2+ forming defects during the initial self‐assembly of cMOF oligomers, which then initiates mesoporous cMOFs via in situ etching. In situ spectroscopy and theoretical simulations further reveal that such a unique perpendicular mesoporous structure shorts the micropore channels by two orders of magnitude and relaxes the inherent ion stacking within micropores, leading to five times faster Na + transport and a remarkable rate capability at 250 C and sodium storage lifespan over 50,000 cycles. Our protocol opens up a new avenue for introducing mesopores into microporous cMOFs for advanced energy applications and beyond.