Fig. 4: In situ spectroscopic analysis.

a In situ Raman spectra of Cu@In(OH)3 for NO3RR test. b Infrared signals in the range of 4000–1000 cm−1 under various potentials for Cu@In(OH)3 during electrocatalytic NO3RR. c in situ DEMS signals of Cu@In(OH)3 for NO3RR test. OCP denotes open-circuit potential. Source data are provided as a Source Data file.