Unveiling Dominant Active Sites in CD3OD Synthesis on Cu-Based Catalysts: Coverage-Dependent Microkinetic Modeling

Abstract

Deuterated methanol (CD₃OD) is widely utilized as a deuterium source in nuclear magnetic resonance solvents and the development of deuterium-labeled pharmaceuticals. However, the predominant active sites and underlying reaction mechanisms governing the synthesis of CD₃OD from CO and deuterium gas (D₂) over Cu-based catalysts remain elusive. In this study, we develop a microkinetic model, incorporating adsorbate–adsorbate interactions based on first-principles calculations, to comprehensively elucidate the mechanism of CO deuteration. This coverage-dependent model highlights the crucial role of intermediate coverage effects, identifying Cu(110) as the dominant active site. At 513.15 K, the model predicts a turnover frequency (TOF) of 1.41 × 10³ s^–1, in good agreement with experimental data, whereas the coverage-independent model yields an unrealistically low TOF of 3.7 × 10^–10 s^–1. Furthermore, the coverage-dependent model successfully reproduces the volcano-shaped trend observed in catalytic activity and selectivity across the entire temperature range, addressing inconsistencies in conventional models. Our findings reveal that Cu(110) and Cu(211) surfaces, enriched with CO and CD₃O species, significantly enhance CD₃OD production. The CD₃O intermediate is identified as the key surface species, with reaction pathways exhibiting substantial variation as a function of surface coverage.