Enhancing magnetite-based oxygen carriers for hydrogen production: The role of pre–oxidation and nickel modification

The pursuit of efficient hydrogen production has driven the development of chemical looping hydrogen generation (CLHG), a promising technology that converts low–calorific–value reducing gases into high–purity hydrogen with minimal environmental impact. However, the limited activity and high cost of oxygen carriers (OCs) have hindered the broader adoption of CLHG. In this study, efficient and low–cost magnetite–based OCs were developed through pre-oxidation and transition metal modification. The results showed that pre–oxidation of magnetite at 900 °C for 2 h significantly increased oxygen vacancy concentration and porosity, boosting hydrogen yield from 0.64 mmol‧g −1 to 3.65 mmol‧g −1 . Further modification with nickel led to a twelvefold enhancement in hydrogen production, achieving 7.60 mmol‧g −1 at 650 °C. Notably, the purity of generated hydrogen exceeded 99.50 % without additional separation procedures. This study also identified sintering as a primary deactivation mechanism, which can be mitigated with an oxygen–assisted regeneration strategy. These findings offer valuable insights for developing efficient OCs and high–purity hydrogen generation from industrial off–gas.