In-situ Infrared Spectroscopy Reveals Electrocatalytic Mechanisms in Hydrogen Isotope Separation

[Background] The separation of hydrogen isotopes (1H, 2H, 3H) is critically important for clean energy and nuclear applications. While electrolytic separation through selective hydrogen/deuterium evolution reactions (HER/DER) offers an environmentally benign approach, its efficiency remains constrained by insufficient understanding of the underlying electrocatalytic mechanisms. [Purpose] This study aimed to elucidate the fundamental mechanisms governing electrocatalytic hydrogen isotope separation by probing the dynamic evolution of surface adsorbates under operational conditions. [Methods] We developed an in-situ electrochemical analysis system coupling external reflection infrared absorption spectroscopy (ER-IRAS). This system was employed to investigate the dynamic evolution of surface adsorbates on Pt/C, Ru/C, PtRu/C, and PtNi/C catalysts during electrolysis. [Results] Our research yielded three key advances: (1) establishment of a comprehensive infrared spectral database identifying 33 characteristic vibrational modes of H/D adsorption species at electrocatalytic interfaces; (2) revelation of a dual-regulation mechanism where metal composition and applied potential synergistically control selectivity, with Pt-based and Ru-based catalysts exhibiting opposing potential-dependent behaviors; and (3) alloying, especially PtRu, boosts deuterium electrolysis selectivity by both tuning the active sites (electronic effect) and enhancing the transport channels (interfacial effect). [Conclusions] This work provides both fundamental insights and practical solutions: the developed in-situ spectroscopic methodology enables unprecedented observation of isotope-specific interfacial processes, while the alloying strategy offers a clear pathway for designing high-performance separation catalysts. These advances significantly propel the technological readiness for industrial implementation of electrolytic isotope separation.