*2.4. X-ray Photoelectron Spectroscopy (XPS)*

Figure 4 and Table 3 summarized the binding energies (BEs) and the X-ray photoelectron spectroscopy (XPS) profiles of La 3d, Co 2p, and Ga 3d for the reduced LCG and LKCG-0.1 catalysts. All XPS profiles showed almost similar peak patterns except the different value of binding energies of each element. The binding energy of Co in the both samples is similar to that of metal cobalt, illustrating that Co exists in the form of Co<sup>0</sup> in the catalyst, which is the same as the XRPD results.

**Figure 4.** X-ray photoelectron spectroscopy (XPS) profiles of La 3d, Co 2p and Ga 3d of the reduced (**a**) LCG and (**b**) LKCG-0.1.

**Table 3.** The binding energies of the reduced LCG and LKCG-0.1 catalysts.


According to the reported literature, the binding energies of La 3d5/2 are 834.4 and 837.8 eV for pure La2O3, 834.7 eV and 838.1 eV for LaGaO3 [26–28]. Herein, the binding energies of La 3d5/2 for LCG are 835.2 eV and 838.6 eV, which is larger than that of pure La2O3 and LaGaO3. The binding energies of Ga 3d5/2 are 17.6 and 19.7 eV, which is also a little larger than that of LaGaO3 at 17.4 and 19.4 eV [28]. The binding energies of Co 2p3/2 is 778.3 eV, which is less than 778.5 eV for metal cobalt [29]. The higher binding energies of La 3d5/2 and Ga 3d5/2, and the lower binding energies of Co 2p3/2 illustrate that an interaction among La, Ga, and Co existed. At the same time, La and Ga could donate elector to Co.

Compared to the reduced LCG catalyst, it was found that the binding energy of La in LKCG-0.1 decreased, suggesting that the doping of K modulated the interaction between La and Ga, which agrees with the above XRPD results. In addition, the binding energy of Co is lower, which means that the K could donate electron to Co. The enhanced electron for Co is beneficial for the selectivity to higher alcohols.

## *2.5. Transmission Electron Microscopy (TEM)*

Figure 5a–h shows the transmission electron microscopy (TEM) images, the line scans profiles, the energy dispersive spectrometer (EDS) mapping scans image, and the elements distribution of the reduced LKCG-0.1 catalyst. In Figure 5a, 5–11 nm Co nanoparticles are uniform dispersed in the reduced LKCG-0.1 catalyst even after 750 ◦C high temperature reduction. In Figure 5b, the lattice spacing of [112] and [011] planes for La2O3, [200] and [111] planes for metal Co, [220] planes for La4Ga2O9 and LaGaO3 can be clearly seen. That is to say, the composition of the reduced LKCG-0.1 catalyst is Co/La2O3-La4Ga2O9-LaGaO3, which is consistent with the XRPD. In addition, as seen from Figure 5b, the metal cobalt nanoparticles are encircled and located between La-Ga-O oxides. And this confinement effect result in the highly dispersion of Co nanoparticles in Figure 5a.

**Figure 5.** Transmission electron microscopy (TEM) images (**a**–**c**), line scanning profiles, energy dispersive spectrometer (EDS) mapping image (**d**), and the elements distribution of La (**e**), K (**f**), Co (**g**), and Ga (**h**) for the reduced LKCG-0.1.

Figure 5c–h exhibits the line scans profiles and the corresponding element distribution of the reduced LKCG-0.1 catalyst. The red lines represent the scanning routes in Figure 5c. Seen from the illustration in Figure 5c, the La and Ga have the same change trend, indicating the formation of La-Ga-O. In addition, there is no La and Ga where Co appears, illustrating metal cobalt nanoparticles are highly dispersed and located between the La-Ga-O oxides, which is in accordance with the XRPD and Figure 5b.

Figure 6a–h displays the TEM images, the line scanning profiles, the EDS mapping image, and the corresponding elements distribution of LKCG-0.1 after 200 h stability tests. As can be seen from Figure 6a, Co is still located between La-Ga-O oxide and the average crystal size of the Co nanoparticles is 9.5 nm, indicating that the sintering of the catalyst is not obvious, which is consistent with the results in Table 2. Seen from the Figure 6b, the lattice spacing of 0.205 and 0.177 nm are assigned to parameters of the [111] and [200] planes of Co; the lattice spacing of 0.228 nm, 0.276 nm, 0.306 nm and 0.294 nm corresponds to the [012], [200], [023], and [103] planes for La2O3, LaGaO3, La4Ga2O9 and La2O2CO3, respectively. That is to say, the component of the LKCG-0.1 catalyst after 200 h reaction is Co/La2O3-La4Ga2O9-LaGaO3-La2O2CO3, which is in accordance with the XRPD results.
