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

Abstract

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 (Ea) 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.