H2, CO, and CH4 were quantified using the Shimadzu GC system equipped with a barrier discharge ionization detector (BID) (Nexis GC-2030). In a typical run, 50 μL of gas sample was injected at a split ratio of 1:1, and flowed into a column (MICROPACKED-ST, Shinwa) with He Wilmad-LabGlass). DSS-d6 was used for the calibration of the 0-ppm position and to quantify the product concentrations as an internal standard. The one dimensional 1 H nuclear Overhauser effect spectroscopy (1D-NOESY; 87) was applied to suppress the water signal.