DOE OSTI · 3015822
Atomic dynamics of gas-dependent oxide reducibility
Abstract
Understanding oxide reduction is critical for advancing metal production, catalysis and energy technologies. Although carbon monoxide (CO) and hydrogen (H 2 ) are widely used reductants, the mechanisms by which they work are often presumed to be similar, both involving lattice oxygen removal. However, because of growing interest in replacing CO with H 2 to lower CO 2 emissions, distinguishing gas-specific reduction pathways is critical. Yet, capturing these atomic-scale processes under reactive gas and high-temperature conditions remains challenging. Here we use environmental transmission electron microscopy, which is capable of real-time, atomic-resolution imaging of gas–solid redox reactions to directly visualize the gas-dependent oxide reduction dynamics in NiO. We show that CO drives surface nucleation and the growth of metallic Ni islands, leading to self-limiting surface metallization. Conversely, H 2 activates a coupled surface-to-bulk transformation, where protons from dissociated H 2 infiltrate the oxide lattice to promote the inward migration of surface-generated oxygen vacancies and enabling bulk metallization. By contrast, oxygen vacancies formed by CO remain confined near the surface, where they rapidly form a metallic Ni layer that inhibits further reduction. Furthermore, these results reveal distinct atomistic pathways for CO and H 2 and provide insights that may guide metallurgical processes and catalyst design.
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Chen, Xiaobo [State University of New York at Binghamton, NY (United States)] (ORCID:0000000329432926), Wang, Jianyu [State University of New York at Binghamton, NY (United States)], Patel, Shyam Bharatkumar [State University of New York at Binghamton, NY (United States)] (ORCID:0000000224497918), Ye, Shuonan [State University of New York at Binghamton, NY (United States)], Wu, Yupeng [State University of New York at Binghamton, NY (United States)], Zhou, Zhikang [State University of New York at Binghamton, NY (United States)] (ORCID:0009000613121495), Qiao, Linna [State University of New York at Binghamton, NY (United States)], Wang, Yuxi [Stony Brook University, NY (United States)], Marinkovic, Nebojsa [Columbia University, New York, NY (United States)] (ORCID:0000000335793453), Li, Meng [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000227454016), Hwang, Sooyeon [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000156066728), Zakharov, Dmitri N. [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000272214812), Ma, Lu [Brookhaven National Laboratory (BNL), Upton, NY (United States)], Wu, Qin [Brookhaven National Laboratory (BNL), Upton, NY (United States)], Boscoboinik, Jorge Anibal [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000250907079), Yang, Judith C. [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000339363864), Zhou, Guangwen [State University of New York at Binghamton, NY (United States)] (ORCID:000000029243293X). 2025-08-20. Atomic dynamics of gas-dependent oxide reducibility. https://doi.org/10.1038/s41586-025-09394-0
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