Fig. 2.

Catalytic performance and in situ DRIFT spectra of the CO₂ + H₂ reaction over different catalysts. a CO₂ conversion, MeOH selectivity, MeOH yield and TOF values as a function of the ZnO particle sizes in different catalysts. b Evolution of the IR spectra over the M-CZZ(16) sample with time. c DRIFT spectra over the M-CZZ(36) sample. d Peak areas of generated intermediate species and methanol during the experiments: areas normalized to the values observed at the end of the transient. Reaction conditions for catalytic test: WHSV = 3 h⁻¹, T = 493 K, CO₂:H₂ = 1:3, P = 3.0 MPa; Reaction conditions for TOF calculation: WHSV = 10 h⁻¹, T = 493 K, CO₂:H₂ = 1:3, P = 3.0 MPa; Reaction conditions for in situ DRIFT spectra: gas flow rate = 40 mL/min, T = 493 K, CO₂:H₂ = 1:3, P = 3.0 MPa. Formate species (2870, 1589, 1386, and 1362 cm⁻¹) and methanol (2975, 2943, 2920, 2871, 2840, and 2818 cm⁻¹) can be observed over the two samples, especially for the M-CZZ(16) catalyst