Hydrogen production by aqueous phase reforming of methanol over stable C-modified NiMgAl hydrotalcite catalyst

Although catalytic aqueous phase reforming (APR) of methanol is a promising hydrogen production method, Ni-based catalysts suffer from low catalyst hydrothermal stability due to severe active metal leaching. To address this problem, NiMgAl hydrotalcite is applied as a support and citric acid as a carbon source to prepare a C-modified NiMgAl hydrotalcite catalyst, and its reaction performance for hydrogen production via methanol APR is evaluated. The introduction of carbon species enhances the interaction between surface Ni and the Mg(Ni,Al)O support, thereby increasing the stability of the catalyst. This enhancement induces the migration of Ni to the catalyst surface, promoting the formation of Ni clusters and exposing more active sites on the catalyst surface. Simultaneously, the carbon modification resulted in smaller Ni particle sizes in the catalyst, which facilitated the reduction of Ni clusters on the catalyst surface. Additionally, part of the NiO was reduced to Ni monomers by carbon and subsequently stabilized, enhancing the activity of the Ni metal on the surface. Compared with the carbon-free NiMgAl catalyst, the C-modified NiMgAl catalyst exhibited an increase in methanol conversion and total hydrogen yield of 83.19% and 82.78%, respectively. Over 17 cyclic reactions are achieved without a sharp decline in hydrogen production yield, implying good hydrothermal stability by anchoring Ni metal sites on the C-modified NiMgAl catalyst.