Metal-carbonate interface promoted activity of Ag/MgCO₃ catalyst for aqueous-phase formaldehyde reforming into hydrogen

Aqueous-phase reforming of biomass-derived formaldehyde is one of efficient and sustainable routes to generate molecular hydrogen as clean energy resource. In this work, Ag/MgCO₃ catalyst is prepared with constructed stable carbonate-modified metal-support interfaces. Under mild and neutral reaction conditions, it exhibits a near an order of magnitude higher low-temperature activity in formaldehyde reforming reaction for producing hydrogen in comparison with Ag/MgO. The catalytic and spectral observations reveal that the Ag/MgCO₃-catalyzed reaction follows an O₂-involved HCHO/H₂O reforming reaction pathway through O₂^[rad]−, ^[rad]OOH and ^[rad]H radicals as highly active intermediates. Ag/MgCO₃ catalyst shows high rates in isotopic H₂-D₂ exchange and HCHO/D₂O reforming reactions and displays an apparent activation energy (E_a) as low as 7.5 kJ mol⁻¹ within 10–50 °C, indicating facile activation of HCHO C[sbnd]H and H₂O O[sbnd]H bonds. Furthermore, Ag/MgCO₃ catalyst adsorbs HCHO molecule in a favorable configuration and strength, as evidenced by the HCHO desorption profile. Comprehensive positive factors benefit to the superior hydrogen production activity of carbonate-modified Ag/MgCO₃ than Ag/MgO.