Co-catalytic enhancement of H2 production by SiO2 nanoparticles

•SiO2 NPs show significant co-catalytic activity for H2-production from HCOOH.•The used homogenous catalyst is an FeII/P(CH2CH2PPh2)3 system.•Co-catalytic activity is attributed to surface Si–O–Si by promoting FA deprotonation.

SiO2 nanoparticles, of varying size 9–55 nm, show significant co-catalytic activity for H2-production from HCOOH by the homogenous FeII/P(CH2CH2PPh2)3 catalyst. Particle size and specific surface area are shown to play key-role in this phenomenon. Larger nanoparticles have better co-catalytic effect. Arrhenius analysis reveals that the significant co-catalytic effect can is attributed to a lowering of the activation energy of the rate-limiting step by ΔEa = 16–36 kJ/mol. This phenomenon is attributed to a thermodynamic promotion of HCOOH deprotonation by the SiO2 nanoparticles, accelerating in this way coordination of HCOO− on the FeII atom of active catalyst, during catalysis. The surface Si–O–Si bridges are shown to be responsible for the promotion of this HCOOH deprotonation, while surface-adsorbed H2O retards the co-catalytic efficiency.

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