The Groundbreaking Discovery in Atomic-Scale Catalysis

In a landmark achievement for catalytic science, researchers from the Dalian Institute of Chemical Physics under the Chinese Academy of Sciences (CAS Dalian) and Southern University of Science and Technology (SUSTech) have unveiled the first direct visualization of bulk oxygen spillover at the atomic scale. Published today in the prestigious journal Nature, this study reveals how oxygen atoms migrate from the lattice of a titanium dioxide support directly to ruthenium metal particles through their interface, challenging long-held assumptions about surface-limited processes in heterogeneous catalysis.

This breakthrough not only deepens our understanding of oxygen transport in catalysts but also opens doors to designing more efficient materials for critical industrial reactions like carbon monoxide oxidation and nitrous oxide decomposition. By harnessing bulk oxygen from the support material, catalysts can sustain higher activity and selectivity, paving the way for greener chemical processes essential to China's push for sustainable energy and environmental protection.

Understanding Oxygen Spillover: From Concept to Atomic Reality

Oxygen spillover refers to the migration of reactive oxygen species from a metal particle to its oxide support or vice versa in heterogeneous catalysts. Traditionally viewed as a surface phenomenon, where oxygen diffuses along the outer layers of the support, this process has been pivotal in enhancing reaction rates for oxidation catalysis. However, its limitations in efficiency and depth have spurred decades of debate.

The CAS Dalian and SUSTech team demonstrates that in Ru supported on rutile-TiO2, oxygen can penetrate deep into the bulk lattice, traveling through dynamically formed channels at the metal-support interface. This bulk spillover bypasses surface constraints, allowing access to vast reservoirs of lattice oxygen within the support. Step-by-step, the process unfolds as follows: oxygen gas adsorbs on Ru, dissociates, and triggers interfacial charge transfer; this strains the subsurface TiO2 lattice reversibly, creating pathways for lattice oxygen to migrate to Ru; the oxygen then participates in reactions like CO oxidation, regenerating vacancies that propagate back into the bulk.

This revelation shifts the paradigm from surface-centric models to interface-dominated bulk activation, with profound implications for catalyst longevity and performance under industrial conditions.

Advanced Techniques Unlock Atomic Insights

The study's power lies in its use of in situ environmental transmission electron microscopy (TEM), which captures real-time dynamics at picometer resolution. Researchers exposed Ru nanoparticles (about 4 nm in size) on TiO2 supports to oxygen, observing atomic displacements as oxygen atoms moved from TiO2 lattice sites to Ru.

• TEM videos show reversible lattice expansion in rutile-TiO2, forming strain-induced channels absent in anatase-TiO2.
• Isotopic labeling with 18O confirmed lattice origin, as oxidized Ru incorporated TiO2's oxygen signature.
• Ambient pressure X-ray photoelectron spectroscopy tracked oxidation states, verifying interior initiation.

Complementing experiments, density functional theory (DFT) simulations quantified low energy barriers (around 1 eV) for oxygen vacancy diffusion in rutile, driven by epitaxial matching at the Ru/TiO2 interface. This synergy of experiment and theory provides irrefutable evidence of the mechanism.

Rutile vs Anatase: The Interface Epitaxy Key

A striking finding is the phase-specificity: bulk spillover thrives in Ru/rutile-TiO2 due to perfect lattice matching (epitaxy), enabling strain adaptability, but fails in Ru/anatase-TiO2 where mismatch blocks subsurface transport. In rutile, Ru(0001)//TiO2(110) alignment facilitates charge redistribution, polarizing Ti-O bonds and easing oxygen release.

This selectivity highlights how subtle structural differences dictate bulk participation. The team extended observations to Ru/SnO2 and Ir/rutile-TiO2, confirming generality for epitaxial interfaces, suggesting a design principle for next-generation catalysts.

Revolutionizing CO Oxidation and Beyond

In practical tests, Ru/rutile-TiO2 excelled in CO oxidation at low temperatures, leveraging lattice oxygen for sustained Mars-van Krevelen cycles—where support oxygen replenishes metal sites. Nitrous oxide decomposition similarly benefited, underscoring applications in exhaust treatment and greenhouse gas mitigation.

Industrially, this could boost processes like selective catalytic reduction (SCR) for NOx and volatile organic compounds (VOCs) abatement, aligning with China's carbon neutrality goals by 2060. Enhanced oxygen utilization reduces noble metal loading, cutting costs and improving scalability.

CAS Dalian: A Powerhouse in Catalysis Innovation

The Dalian Institute of Chemical Physics (DICP-CAS), a flagship of China's Academy of Sciences, leads global catalysis research. Home to the State Key Laboratory of Catalysis, DICP pioneered single-atom catalysis and boasts achievements in Fischer-Tropsch synthesis and photocatalysis. Lead authors Weijue Wang, Xiaofeng Yang, Wei Liu, Yanqiang Huang, and Tao Zhang hail from here, building on institute director Tao Zhang's Citation Laureate award for single-atom concepts.

DICP's multidisciplinary approach integrates synthesis, spectroscopy, and computation, fostering breakthroughs like this spillover visualization.

SUSTech: Rising Star in Materials Chemistry

Southern University of Science and Technology, Shenzhen's innovative young university founded in 2011, contributed theoretical expertise via Hongbin Xu and Yang-Gang Wang from the Department of Chemistry. SUSTech emphasizes frontier research, with strengths in electrocatalysis and computational chemistry.

Collaborations like this exemplify SUSTech's role in bridging theory and experiment, accelerating China's higher education ascent in global rankings.

Implications for Sustainable Chemistry in China

China, the world's largest chemical producer, faces pressure to decarbonize. This spillover mechanism promises catalysts for efficient ammonia oxidation, methane reforming, and fuel cell oxygen reduction reactions (ORR). By activating bulk oxygen, supports like TiO2 become active participants, minimizing waste and enhancing durability under harsh conditions.

Environmentally, it supports cleaner propylene oxide production and auto exhaust systems, reducing emissions. Economically, lower precious metal use aligns with resource efficiency drives.

Future Horizons: Engineering Interfaces for Tomorrow's Catalysts

Looking ahead, researchers aim to generalize bulk anion spillover to other metals/oxides, targeting proton exchange membrane fuel cells and CO2 valorization. DICP and SUSTech plan interface doping and nanostructuring to tune epitaxy, potentially yielding 10-fold activity boosts.

• Explore spillover in single-atom catalysts for ultra-low loading.
• Integrate with operando spectroscopy for reaction dynamics.
• Scale-up for pilot plants in Dalian's clean energy labs.

This work cements China’s leadership in catalysis, inspiring university programs to prioritize interface science.

China's Catalysis Ecosystem: Universities Driving Innovation

Beyond DICP and SUSTech, institutions like Tsinghua and Peking University amplify national efforts. Government initiatives, including the 14th Five-Year Plan, fund such research, with CAS institutes mentoring PhD students via University of Chinese Academy of Sciences. SUSTech's rapid rise—from startup to global contender—exemplifies reform-era higher education success, attracting talent to Shenzhen's innovation hub.

For aspiring chemists, opportunities abound in faculty positions and postdocs at these vanguard labs.

Photo by Markus Winkler on Unsplash