failure over large areas. This implies that the critical feature at play in the generation of mega-earthquakes is not the amplitude of shear strength
but its spatial variations. Thus, the absence of
asperities on large faults may counterintuitively
be a source of higher hazard. Though our study
focused on subduction earthquakes, flatness may
favor large earthquakes on long strike-slip faults
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We thank R. Bürgmann for his valuable comments on the
manuscript. The slab1.0 model is available online at earthquake.
usgs.gov/data/slab/. The U.S. Geological Survey catalog of
historical earthquakes (M ≥ 8.0 since 1900) that we used in this
study can be found at http://earthquake.usgs.gov/earthquakes/
world/ historical.php. For the subduction zones that have not
experienced any M ≥ 8.0 earthquakes since 1900, this catalog
was complemented by the Global Centroid Moment Tensor
catalog ( www.globalcmt.org/). We used Generic Mapping Tools
to compute the distributions of dip-angle gradients ( gmt.soest.
hawaii.edu/). This work was supported by NSF grant EAR-1520238,
ANR project TO-EOS, and the French Ministry of Research
Materials and Methods
Figs. S1 to S8
Tables S1 to S2
6 May 2016; accepted 19 October 2016
Direct and continuous strain control
of catalysts with tunable battery
Haotian Wang,1 Shicheng Xu,2 Charlie Tsai,3,4 Yuzhang Li,5 Chong Liu,5 Jie Zhao,5
Yayuan Liu,5 Hongyuan Yuan,6 Frank Abild-Pedersen,4 Fritz B. Prinz,2,5
Jens K. Nørskov,3,4 Yi Cui5,7*
We report a method for using battery electrode materials to directly and continuously control
the lattice strain of platinum (Pt) catalyst and thus tune its catalytic activity for the oxygen
reduction reaction (ORR). Whereas the common approach of using metal overlayers introduces
ligand effects in addition to strain, by electrochemically switching between the charging and
discharging status of battery electrodes the change in volume can be precisely controlled to
induce either compressive or tensile strain on supported catalysts. Lattice compression and
tension induced by the lithium cobalt oxide substrate of ~5% were directly observed in
individual Pt nanoparticles with aberration-corrected transmission electron microscopy. We
observed 90% enhancement or 40% suppression in Pt ORR activity under compression or
tension, respectively, which is consistent with theoretical predictions.
Highly efficient electrocatalysts for renewable nergy conversion processes, such as in H2 fuel cells and water-splitting electro- catalysis, is becoming increasingly impor- tant (1–3). One strategy for systematically
improving the activities of known catalysts is to
modify their electronic structure (4–6). Numerous
examples have been demonstrated in H2O–O2–H2
electrocatalysis, such as the changing of d band
filling in perovskite oxides for oxygen evolution
(7), transition-metal alloying for the oxygen reduction reaction (ORR) (4, 8–11), and our recent
studies of using lithium (Li)–ion intercalation
and extraction in layered materials for water-splitting (12, 13).
Lattice strain, either compressive or tensile,
can alter the surface electronic structure by mod-
ifying the distances between surface atoms and
in turn catalytic activity (14–17). For platinum
(Pt), previous studies have suggested that the
5d-band center of Pt can be shifted by ~0.1 eV with
only 1% lattice strain (18), which can appreciably
strengthen or weaken bonding of reaction inter-
mediates to the surface (14, 18). Lattice-mismatch
between metals can be generated by directly
synthesizing core-shell structures (19–23) or by
selectively removing atoms from an alloy (for
example, stripping away Cu from a Pt-Cu alloy)
(8, 14, 24–26). However, because of the larger
lattice of Pt as compared with that of most metal
cores, this method is typically restricted to com-
pressive strain (14, 27). Additionally, both elec-
tronic charge transfer between the different metal
atoms (ligand effects) and changes in the surface
stability—and thus surface area—are present,
making it difficult to identify and control the
effects of strain alone (14, 25). Another strategy
is to deposit catalysts onto flat substrates that
undergo physical transformations as external
forces are applied or the temperatures varied
(28, 29). Those flat and tunable substrates pre-
sent great importance to fundamental analysis,
but only a few of them have been successfully
demonstrated effective in electrocatalysis (28).
Thus, new methods that can flexibly and effec-
tively control both tensile and compressive lattice
strain in catalysts without introducing additional
effects are needed.
1Department of Applied Physics, Stanford University,
Stanford, CA 93205, USA. 2Department of Mechanical
Engineering, Stanford University, Stanford, CA 93205, USA.
3SUNCAT Center for Interface Science and Catalysis,
Department of Chemical Engineering, Stanford University,
Stanford, CA 94305, USA. 4SUNCAT Center for Interface
Science and Catalysis, SLAC National Accelerator Laboratory,
2575 Sand Hill Road, Menlo Park, CA 94025, USA.
5Department of Material Science and Engineering, Stanford
University, Stanford, CA 94305, USA. 6Department of
Physics, Stanford University, Stanford, CA 94305, USA.
7Stanford Institute for Materials and Energy Sciences, SLAC
National Accelerator Laboratory, 2575 Sand Hill Road, Menlo
Park, CA 94025, USA.
*Corresponding author. Email: firstname.lastname@example.org