Highly Efficient Photothermocatalytic CO₂ Reduction in Ni/Mg‐Doped Al₂O₃ with High Fuel Production Rate, Large Light‐to‐Fuel Efficiency, and Good Durability

Abstract

A novel nanocomposite of Ni nanoparticles loaded on Mg‐doped Al2O3 (Ni/Mg‐Al2O3) was prepared. By photothermocatalytic CO2 reduction with methane (CRM) merely using focused UV‐vis‐IR illumination on Ni/Mg‐Al2O3, high production rates of H2 (rnormalH2, 69.71 mmol min−1 g−1) and CO (rCO, 74.57 mmol min−1 g−1) and an extremely large light‐to‐fuel efficiency (η, 32.9%) are acquired. High rnormalH2 and rCO (51.07 and 59.66 mmol min−1 g−1) and a large η (32.5%) are acquired even by using focused λ > 560 nm vis‐IR illumination. Ni/Mg‐Al2O3 shows good durability for photothermocatalytic CRM due to the side reaction of carbon deposition being enormously inhibited in comparison with a reference catalyst of Ni nanoparticles loaded on Al2O3. The enormous carbon deposition inhibition is ascribed to the presence of a fence of CO2 molecules (strongly adsorbed on Mg‐doped Al2O3) around Ni nanoparticles, which block the polymerization and growth of carbon species to nanofibers by promoting the oxidation of carbon species formed by CH4 dissociation. The high photothermocatalytic activity of Ni/Mg‐Al2O3 arises from efficient light‐driven thermocatalytic CRM. A photoactivation is found to considerably raise the photothermocatalytic activity of Ni/Mg‐Al2O3 because of the apparent activation energy (Ea) being substantially decreased upon focused illumination. The Ea reduction is associated with the rate‐determining steps of CRM (e.g., CH4 dissociation and the oxidation of carbon species) being accelerated upon focused illumination.

Photothermocatalytic Dry Reforming of Methane for Efficient CO2 Reduction and Solar Energy Storage

“…To further improve η, a novel composite of Ni nanoparticles supported on Mg-doped Al 2 O 3 (Ni/Mg–Al 2 O 3 ) was synthesized. In this case, a very large η (32.9%) is obtained by photothermocatalytic DRM due to the very high r H2 and r CO values (69.71 and 74.57 mmol min –1 g –1 ) obtained …”

A Novel Synergetic Effect Between Ru and CeO2 Nanoparticles Leads to Highly Efficient Photothermocatalytic CO2 Reduction by CH4 with Excellent Coking Resistance

“…In accordance with the weight loss, we calculated the coke formation rate (r C ) of Ru/CeO 2 during the 40 h of photothermocatalytic stability experiment. Ru/CeO 2 shows an extremely low r C of 5.26 Â 10 À5 g C g À1 catalyst h À1 (Figure 6C), which is much lower than that of nonprecious metal (e.g., Ni, Co) [35][36][37][38]41,42] catalysts and precious metal catalysts (e.g., Ru) [39] for photothermocatalytic CRM. No carbon nanofibers were detected in the used Ru/CeO 2 through TEM characterization (Figure S2A, Supporting Information), which is in keeping with the result of TG-MS.…”

“…The role of oxygen vacancies of CeO 2 in Ru/CeO 2 formed by O atoms of CeO 2 being participated in carbon oxidation was explored by temperature-programmed CO 2 desorption. As demonstrated in Figure9, Ru/Al 2 O 3 shows a strong CO 2 desorption peak around 78 C, which is ascribed to the adsorption of CO 2 on the basic sites of Al 2 O 3 [35,50]. Ru/CeO 2 shows a strong CO 2 desorption peak around 126 C, much higher than that of Ru/Al 2 O 3 .…”

“…Extensive efforts have been devoted to tackling the challenges by designing various efficient photocatalysts which could utilize visible, even infrared, energy in sunlight. Recently, the strategies of photothermocatalytic CO 2 reduction by H 2 O, [22][23][24][25][26] H 2 , [27][28][29][30] and CH 4 [31][32][33][34][35][36][37][38][39][40][41][42] have been developed. They have attracted more and more interest as they could integrate the advantages of both thermocatalytic CO 2 reduction (high catalytic efficiency) [43,44] and photocatalytic CO 2 reduction (light-to-fuel conversion), and fully utilize solar energy including UV, visible, and infrared energy.…”

“…[22][23][24][25][26][27][28][29][30] Among the strategies, photothermocatalytic CO 2 reduction by CH 4 to produce CO and H 2 (CRM, CO 2 þ CH 4 ¼ 2CO þ 2H 2 , ΔH 298 ¼ 247 kJ mol À1 ) by using nanostructured group VIII metal nanoparticles as catalysts is especially attractive, as it could not only convert the two greenhouse gases to fuels but also simultaneously achieve high r fuel and η. [35][36][37][38][39][40][41][42] For the photothermocatalytic CRM strategy, there are two key challenges to be addressed. One is to continuously improve r fuel and η.…”