Correction to: Nature Catalysis https://doi.org/10.1038/s41929-017-0016-y, published online 29 January 2018.

In the version of this Article originally published online, in Fig. 2b, the y axis unit incorrectly included superscript –1 on Ni; it should have been just Ni. In the PDF only, in Fig. 2d–f, the label ‘Particle size (nm)’ was missing from the x axes. All of these corrections have now been made.