Photo-assisted chemical looping toluene reforming for improved hydrogen and syngas Co-production under mild conditions

The conventional chemical looping reforming and water splitting (CLRWS) process is hindered by its requirement for high-temperature operation, which leads to challenges such as oxygen carriers (OCs) sintering and deactivation. In this study, we propose a photo-assisted chemical looping strategy that operates under milder conditions for efficient co-production of hydrogen and syngas. Four typical iron-based spinel oxides were tested as potential OCs, among which the NiFe2O4 exhibited superior reaction performance. Considering the yield and purity of both syngas and hydrogen, 600 °C was identified as the optimal reaction temperature when NiFe2O4 was used as the oxygen carrier (OC). At this condition, the system can achieve a hydrogen yield of 8.24 mmol/g OC with 97.81% purity and a syngas yield of 2.57 Nm3/kg C7H8 with 86.50% purity. This performance was close to that achieved at 750 °C without light. Results demonstrated that light illumination reduced the optimal reaction temperature by 150 °C. The introduction of light into CLRWS enables photothermal heating and generates electron-hole pairs (EHPs), which facilitate the formation of oxygen vacancies (Vo) and singlet oxygen (1O2), thereby enhancing lattice oxygen mobility and fuel oxidation kinetics. This synergistic mechanism enables efficient toluene conversion and water splitting under mild conditions. This work provides valuable insights for addressing the series of challenges caused by high temperatures in chemical looping processes and validates the photo-assisted approach as an effective route to lower operating temperatures and enhance hydrogen production.