Valorization of a Bio-Oil Model Compound to Green Hydrogen: Enhanced Photothermal Reforming on Cobalt Catalysts with TiO 2 -Carbon Hybrid Support

Photothermal coupled catalysis was adopted as an advanced strategy for hydrogen production via steam reforming of bio-oil. Four composite catalysts, namely, Co/TiO2-EG (sol–gel), Co/TiO2-CNTs (mixing), Co/TiO2, and Co/TiO2-CNTs (sol–gel), were synthesized via distinct fabrication routes. Results of thermal catalytic performance tests showed that Co/TiO2-CNTs (sol–gel) exhibited the optimal low-temperature activity. At 450 °C, Co/TiO2-CNTs (sol–gel) achieved a hydrogen yield of 71.8% and a carbon conversion of 91.13%, which were 185.15% and 147.43% higher than those of Co/TiO2-CNTs (mixing) (25.18% and 36.83%, respectively). The activity order of the four catalysts was determined as Co/TiO2-CNTs (sol–gel) > Co/TiO2-EG (sol–gel) > Co/TiO2 > Co/TiO2-CNTs (mixing), with the two catalysts prepared by the sol–gel approach showing significantly better performance than the other two. TEM and H2-TPR results indicate that the sol–gel method improves the dispersion of Co oxides on the support surface. After introducing photothermal synergistic catalysis, Co/TiO2-EG (sol–gel) and Co/TiO2-CNTs (sol–gel) displayed superior catalytic performance at 450 °C compared with Co/TiO2 and Co/TiO2-CNTs (mixing); specifically, the hydrogen yield of Co/TiO2-EG (sol–gel) was 10.56% higher than that of Co/TiO2-CNTs (sol–gel). As the temperature was raised to 500 °C, both Co/TiO2-CNTs (sol–gel) and Co/TiO2-EG (sol–gel) achieved a 100% hydrogen yield as well as a 100% carbon conversion. Compared to CNT-modified catalysts, the EG composite support was more effective in narrowing the band gap by an additional 0.09 eV, thus promoting electron excitation. Consequently, the sol–gel-synthesized catalysts exhibited superior photothermal synergy, with Co/TiO2-CNTs (sol–gel) excelling in low-temperature thermal catalysis and Co/TiO2-EG (sol–gel) demonstrating outstanding performance in photothermal systems.