Synergistic, dual energy source production of hydrogen using Ru-promoted nitrogen-doped carbon nanotubes

In this work, ruthenium-promoted nitrogen-doped carbon nanotubes (Ru/NCN) composite materials were synthesized and utilized for the dual thermo-photo catalytic production of hydrogen using biomass-derived reactants. A spectroscopic and microscopy-based characterization showed that the composites contain rather small metallic ruthenium entities uniformly distributed and stabilized through interaction with the carbon-containing component. A highly active and (under reaction conditions) stable Ru/NCN material maximized hydrogen output under continuous operation, showing outstanding reaction rates up to ca. 30 mmol g−1 h−1 and quantum efficiencies of ca. 7.5 %. The synergy reached by the combined use of two energy sources was studied quantitatively and analyzed in the temperature range going from room temperature to 300 °C. The combination of heat and light triggers a mechanism by which the bio-molecule, methanol, is activated by light-triggered hydroxyl-type radical species and promotes the reaction up to temperatures close to 300 °C. The new composite materials based on nitrogen-doped carbon nanotubes show thus high potential to improve classic, thermal-based processes for hydrogen production. [Display omitted] •Hydrogen thermo-photo production using Ru-promoted N-doped Carbon nanotubes.•Optimum catalyst with a 1 wt% of Ru allows synergistic use of the two energy sources.•Catalyst is stable under long term operation conditions.•Nitrogen-doping appears as a key parameter to drive functional properties.