Fig. 1
Overall mechanism and phenomena of water-forming reaction at FP etalon. a Layer description of FP etalon and H2/O2 adsorption on the Pd surface undergoing the atomic-level catalytic reaction. b Energy profiles for dissociative adsorption of H2/O2 and H2O formation/desorption on the Pd(111) surface initially exposed to O2 (black) and H2 (red). c-f Conceptual illustrations of atomical gas adsorption and sequential water-forming reactions inducing water bubble formation over the O2-precovered (c) and H2-precovered Pd surface (d) in response to H2/O2 gases exposure, resulting in optical foggy effect (e) and optical whiteout effect (f), respectively