The catalytic properties of 1wt % Ru catalysts with the same mean Ru cluster size of 1.4-1.5nm supported on herringbone-type carbon nanofibers with different N contents were compared for H2 production from formic acid decomposition. The Ru catalyst on the support with 6.8wt % N gave a 1.5-2times higher activity for the dehydrogenation reaction (CO2, H2) than the catalyst on the undoped support. The activity in the dehydration reaction (CO, H2O) was the same. As a result, the selectivity to H2 increased significantly from 83 to 92 % with N-doping, and the activation energies for both reactions were close (55-58kJ mol-1). The improvement could be explained by the presence of Ru clusters stabilized by pyridinic N located on the open edges of the external surface of the carbon nanofibers. This N may activate formic acid by the formation of an adduct (>NH+HCOO-) followed by its dehydrogenation on the adjacent Ru clusters. Nanoparticles on nanofibers: Ru catalysts on N-doped carbon nanofibers show a higher selectivity for hydrogen production from formic acid decomposition compared to undoped samples. This is attributed to the activation of formic acid on the pyridinic sites of the support followed by dehydrogenation on adjacent Ru clusters.
- supported catalysts