*2.1. Particle Size of the Catalysts*

As seen in Figure 1, SEM images of the unreacted catalysts were taken in order to measure the average particle size. The approximate diameters of the particles of each the catalysts before the hydrothermal reaction were as follows: Cu: 400 μm; Ni: 9 μm; Pd/C: 25 μm; C: 55 μm; Ru/C: 175 μm; Fe2O3; Fe3O4: 93 μm.

**Figure 1.** SEM images of the catalyst particles.
