Lattice Hydrogen as an Active Reaction Mediator in Electrocatalysis

Abstract

Traditionally, electrocatalysis has been conceptualized through a surface-centric model, wherein hydrogen is seen just as a transient adsorbate adhering to the Sabatier principle. Lattice hydrogen fundamentally challenges the surface-centric paradigm by acting as an active, cohesive reaction mediator that redefines electrocatalytic mechanisms. We illustrate that electrochemically produced lattice hydrogen in metal hydrides and hydrogenated lattices function as a dynamic protonelectron reservoir, directly participating in bond formation, stabilizing essential intermediate, utilizing recent progress in the hydrogen evolution reaction (HER), carbon dioxide reduction (CO2RR), nitrogen reduction reaction (NRR), and nitrate reduction reaction (NO3RR). Lattice 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 lattice hydrogen to achieve exceptional activity, selectivity, and durability in advanced electrocatalytic systems by reconceptualizing catalysts as hydrogen-responsive, adaptable materials rather than static surfaces.