Investigation of intermediates formation in the CO2 hydrogenation to methanol reaction over Ni5Ga3-ZrO2-SBA-15 materials prepared via ZrO2 atomic layer deposition

The production of methanol through CO2 hydrogenation holds great promise for efficient CO2 utilization. The development of catalysts that exclusively favor the formate route is desirable as this enhances methanol selectivity and avoids CO formation. Here, the synthesis of two groups of Ni5Ga3-ZrO2-SBA-15 based materials was studied through the atomic layer deposition (ALD) of ZrO2. The first group was prepared applying ZrO2 ALD over a Ni5Ga3/SBA-15 material and the second group was prepared doing ZrO2 ALD over a mesoporous silica, Santa Barbara Amorphous (SBA-15), followed by impregnation with Ni5Ga3. Some characterization techniques were employed to assess the effectiveness of the ZrO2 ALD on both groups. Interestingly, it was observed that ZrO2 deposition was less effective over the Ni5Ga3/SBA-15 sample compared to its deposition over pure SBA-15, and through XPS analysis was noticed that ZrO2 is probably covering part of the Ni5Ga3 alloys. Furthermore, in situ DRIFTS analysis was performed during reaction conditions and revealed that ZrO2 deposition facilitated the formation of formate and methoxy intermediates in both material groups. The increase in the ZrO2 ALD cycles increased the formate and methoxy bands and decreased CO-related bands. After 6 cycles, only the ZrSBANG_6 catalyst exclusively followed the formate route, as only formate and methoxy bands were present.