Fig. 4.

Water activation. a Cu LMM AES and b O 1 s XPS spectra of various Cu NCs (black lines), Cu NCs exposed to H₂O at 423 K (red lines), Cu NCs exposed to H₂O at 523 K (blue lines) and Cu NCs exposed to H₂O at 523 K and then to CO at 473 K (brown lines). All spectra were measured without exposure to air