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Edited by Alexis T. Bell, University of California, Berkeley, CA, and approved February 13, 2018 (received for review December 20, 2017)
Significance
While research on single-atom catalysts (SACs) is arguably mature, rare work has been done on atomically dispersed catalyst featuring two atoms. We synthesized Ir dinuclear heterogeneous catalyst in a facile photochemical way. It exhibits outstanding stability and high activity toward water oxidation. The significance of this work can also be appreciated from the catalysis perspective. A grand challenge in heterogeneous catalysis is how to understand the detailed mechanisms at the molecular level, because the most active heterogeneous catalysts are often poorly defined in their atomic structures. Our finding is built upon recent advances aimed at studying SACs but takes a crucial step forward. It provides a material platform to study reactions that would require more than one active site.
Abstract
Atomically dispersed catalysts refer to substrate-supported heterogeneous catalysts featuring one or a few active metal atoms that are separated from one another. They represent an important class of materials ranging from single-atom catalysts (SACs) and nanoparticles (NPs). While SACs and NPs have been extensively reported, catalysts featuring a few atoms with well-defined structures are poorly studied. The difficulty in synthesizing such structures has been a critical challenge. Here we report a facile photochemical method that produces catalytic centers consisting of two Ir metal cations, bridged by O and stably bound to a support. Direct evidence unambiguously supporting the dinuclear nature of the catalysts anchored on α-Fe2O3 is obtained by aberration-corrected scanning transmission electron microscopy (AC-STEM). Experimental and computational results further reveal that the threefold hollow binding sites on the OH-terminated surface of α-Fe2O3 anchor the catalysts to provide outstanding stability against detachment or aggregation. The resulting catalysts exhibit high activities toward H2O photooxidation.
Footnotes
↵1Y.Z. and K.R.Y. contributed equally to this work.
↵2Z.W., X.Y., S.C., and Y.Y. contributed equally to this work.
- ↵3To whom correspondence may be addressed. Email: gary.brudvig{at}yale.edu, victor.batista{at}yale.edu, or dwang{at}bc.edu.
Author contributions: Y.Z. and D.W. designed research; Y.Z., K.R.Y., Z.W., X.Y., S.C., Y.Y., Q.D., X. Zhang, J.E.T., L.J., K.L.M., A.T., H.B., S.C.F., X. Zhong, P.W., X.P., J.G., M.F.-S., G.W.B., and V.S.B. performed research; X.Z., P.W., and X.P. supervised the HAADF-STEM efforts; M.F.-S. supervised DRIFTS experiments; Y.Z., K.R.Y., Z.W., X.Y., L.J., X.P., J.G., M.F.-S., G.W.B., V.S.B., and D.W. analyzed data; and Y.Z. and D.W. wrote the paper with comments from all authors.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1722137115/-/DCSupplemental.
Published under the PNAS license.
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Stable iridium dinuclear heterogeneous catalysts supported on metal-oxide substrate for solar water oxidation
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