Interstitial hydrogen as an active reaction mediator in electrocatalysis

초록

Traditionally, electrocatalysis has been conceptualized through a surface-centric model, wherein hydrogen is seen just as a transient adsorbate adhering to the Sabatier principle. Interstitial hydrogen fundamentally challenges the surface-centric paradigm by acting as an active cohesive reaction mediator that redefines electrocatalytic mechanisms. We illustrate that electrochemically produced interstitial hydrogen in metal hydrides and hydrogenated lattices functions as a dynamic proton–electron reservoir, directly participating in bond formation, stabilizing essential intermediates, utilizing recent progress in the hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO2RR), nitrogen reduction reaction (NRR), nitrate reduction reaction (NO3RR) and hydrogen oxidation reaction (HOR). Interstitial hydrogen, conversely, engenders bulk-surface cooperativity, disrupts conventional scaling relationships, and unveils reaction pathways inaccessible to classical surface models. We discuss novel design ideas, experimental challenges, and theoretical deficiencies that arise in the pursuit of identifying and modeling hydrogen transport across bulk–interface boundaries. This review introduces a conceptual framework for employing interstitial hydrogen to achieve exceptional activity, selectivity, and durability in advanced electrocatalytic systems by reconceptualizing catalysts as hydrogen-responsive, adaptable materials rather than static surfaces.

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