DOE OSTI · 3015823
Oscillatory redox behavior in oxides: Cyclic surface reconstruction and reactivity modulation via the Mars–van Krevelen mechanism
Abstract
The breaking of translational symmetry at oxide surfaces gives rise to coordinatively unsaturated cations/anions and surface restructuring—key factors that govern surface reactivity. Using direct in situ environmental transmission electron microscopy (TEM) observations along with atomistic modeling, we report oscillatory redox behavior in CuO under H 2 , where cyclic surface reconstruction and reactivity modulation occur via the Mars–van Krevelen (MvK) mechanism. We observe self-switching between oxygen-rich and oxygen-deficient surface reconstructions, alternately activating and deactivating the surface for H 2 O formation. During periods of chemical inactivity, the oxygen-deficient surface undergoes slow reoxidation via lattice oxygen diffusing from subsurface and bulk reservoirs, restoring the active oxygen-rich surface termination. The inherent disparity in chemical activity among undercoordinated surface ions, along with sluggish subsurface-to-surface oxygen replenishment, drives this oscillatory redox cycle, modulating H2-induced loss of lattice oxygen at the surface and its delayed replenishment from the subsurface. This creates spatiotemporally separated redox steps at the oxide surface. The phenomena and atomistic insights presented here have significant implications for manipulating the surface reactivity of oxides by tuning the separation of these redox steps.
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Sun, Xianhu [State University of New York, Binghamton, NY (United States); University of Chinese Academy of Sciences, Beijing (China)] (ORCID:0000000295092950), Wu, Dongxiang [State University of New York, Binghamton, NY (United States)] (ORCID:0000000298085377), Wang, Jianyu [State University of New York, Binghamton, NY (United States)], Patel, Shyam B. [State University of New York, Binghamton, NY (United States)] (ORCID:0000000224497918), Zhu, Wenhui [State University of New York, Binghamton, NY (United States)], Yang, Ji [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)], Yang, Timothy T. [University of Pittsburgh, PA (United States)] (ORCID:0000000257850511), Ye, Shuonan [State University of New York, Binghamton, NY (United States)], Chen, Xiaobo [State University of New York, Binghamton, NY (United States)] (ORCID:0000000329432926), Zhu, Yaguang [State University of New York, Binghamton, NY (United States)], Qiao, Linna [State University of New York, Binghamton, NY (United States)], Li, Meng [University of Pittsburgh, PA (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000227454016), House, Stephen D. [University of Pittsburgh, PA (United States)] (ORCID:0000000320356373), Su, Ji [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:000000032258162X), Saidi, Wissam A. [University of Pittsburgh, PA (United States)] (ORCID:0000000167144832), Boscoboinik, Jorge Anibal [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000250907079), Yang, Judith C. [University of Pittsburgh, PA (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States)], Sharma, Renu [National Institute of Standards and Technology, Gaithersburg, MD (United States)], Zhou, Guangwen [State University of New York, Binghamton, NY (United States)] (ORCID:000000029243293X). 2025-05-11. Oscillatory redox behavior in oxides: Cyclic surface reconstruction and reactivity modulation via the Mars–van Krevelen mechanism. https://doi.org/10.1073/pnas.2422711122
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