Efficient hydrogen production from formic acid dehydrogenation over ultrasmall PdIr nanoparticles on amine-functionalized yolk-shell mesoporous silica.

[Display omitted] • Novel yolk-shell Pd 4 Ir 1 /YSMSNs-NH 2 catalyst with highly dispersed PdIr alloy NPs was prepared. • The radially oriented mesoporous channels of Pd 4 Ir 1 /YSMSNs-NH 2 catalyst can promote mass transfer and increase accessibility. • The amine groups on the YSMSNs-NH 2 support can improve the dispersion and reduce the particle size of the PdIr active phases. • The ultrasmall size (1.4 nm) and high dispersion of PdIr alloy NPs could expose more catalytic active sites. • The Pd 4 Ir 1 /YSMSNs-NH 2 catalyst exhibits an initial TOF value of 5818 h−1 at 50 °C, with 100 % FA conversion and H 2 selectivity. Developing heterogeneous catalysts with exceptional catalytic activity over formic acid (HCOOH, FA) dehydrogenation is imperative to employ FA as an effective hydrogen (H 2) carrier. In this work, ultrasmall (1.4 nm) and well-dispersed PdIr nanoparticles (NPs) immobilized on amine-functionalized yolk-shell mesoporous silica nanospheres (YSMSNs) with radially oriented mesoporous channels have been synthesized by a co-reduction strategy. The optimized catalyst Pd 4 Ir 1 /YSMSNs-NH 2 (Pd/Ir molar ratio = 4:1) exhibited a remarkable turnover frequency (TOF) of 5818 h−1 and remarkable stability at 50 °C with the addition of sodium formate (SF), resulting in complete FA conversion and H 2 selectivity, exceeding most of the solid heterogeneous catalysts in previous reports under similar circumstances. Kinetic isotope effect (KIE) exploration indicates the cleavage of the C H bond is regarded as the rate-determining step (RDS) during the FA dehydrogenation process. Such excellent catalytic properties arise from the ultrafine and well-dispersed PdIr NPs supported on the nanosphere support YSMSNs-NH 2 , the electronic synergistic effect of PdIr alloy NPs, and the strong metal-support interaction (MSI) effect between the introduced PdIr NPs and YSMSNs-NH 2 support. This work offers a new paradigm for exploiting the highly effective silica-supported Pd-based heterogeneous catalysts over the dehydrogenation of FA. [ABSTRACT FROM AUTHOR]