Synthesis Of Rh/(Ag,Ni,Co) Bimetallic Nanoparticles And Their Catalytic Activity For Hydrogen Generation

Hydrogen is recognized to be an ideal clean and safety alternative energy source with high energy density.Catalytic hydrogen generation from alkaline potassium borohydride by metallic nanocatalyst is regard as one of the most promising route.A series of ISOBAM-104 protected colloidal Ag,Rh/Ag,Rh/Ni,Rh/Co and Ag/Pt metallic nanoparticles were synthesized via co-reduction of corresponding metal precursors by rapid injection of KBH₄.Ultraviolet-visible spectrophotometry（UV-Vis）,X-ray photoelectron spectroscopy（XPS）,transmission electron microscopy（TEM）,powder X-ray diffraction（XRD）and high-resolution transmission electron microscopy（HR-TEM）equipped with energy dispersive spectrometer（EDS）were combined to characterize the morphology,size,crystalline structure,metal composition and electron distribution of the as-prepared nanoparticles（NPs）.The effects of ISOBAM-104 usage(molar ratio of ISOBAM-104 to Ag+,denoted as R_ISO)and precursor concentration(C_AgClO4 or CAgNO₃,denoted as CM)on size and morphology of Ag NPs were investigated in detail.In addition,the effects of metal composition of Rh（Ag,Ni,Co）and Ag/Pt bimetallic nanoparticles（BNPs）on the catalytic activity for hydrogen generation from the hydrolysis of an alkaline KBH₄ solution were studied.The catalytic kinetics of Rh/Ag and Rh/Ni BNPs for the hydrolysis of alkaline KBH₄ solution were also studied.The results indicated that:（1）ISOBAM-104 can be acted as an effective protective agent for the synthesis of evenly small sized Ag NPs using AgClO₄ or AgNO₃ as precursors with R_ISO and CM within the range of 20 to 480,0.0138 mM to 1.32 mM,respectively.The as-prepared Ag NPs showed superior stability and dispersibility without obviously morphology change and size increase after storage at ambient condition for one year.And the Ag NPs synthesized at R_ISO=40,C_AgClO4=0.22 mM with an average size of 1.4±0.4 nm exhibits excellent antibacterial activity for E.coli（DH5α）with MIC and MBC of about 0.25 mg/L and 0.50 mg/L,respectively.（2）A series of ISOBAM-104 protected alloy structured Rh/Ag BNPs were synthesized by co-reduction of corresponding metal precursors by rapid injection of KBH₄.And the as-prepared Rh/Ag BNPs showed much higher catalytic activity than that of monometallic Ag and Rh nanoparticles（MNPs）.Rh₁₀Ag₉₀ BNPs showed higher catalytic activity of about can be 15480 mol-H₂·h^-1·mol-Rh^-1 among all the as-prepared BNPs.The higher catalytic activity of the Rh/Ag BNPs than that of corresponding MNPs can be ascribed to electronic charge transfer effects among Ag and Rh atoms,which is supported by the result of X-ray photoelectron spectroscopy（XPS）and density functional theory（DFT）calculation.The reaction order of KBH₄ concentration to Rh₈₀Ag₂₀ and Rh₂₀Ag₈₀ BNPs were determined to be 0.61 and 0.27.Rh₈₀Ag₂₀ and Rh₂₀Ag₈₀ BNPs respectively showed a low apparent activation energy of 48.5±3.7 kJ/mol and 44.2±6.2 kJ/mol in the present experiments.（3）A series of ISOBAM-104 protected alloy structured Rh/Ni BNPs were synthesized by co-reduction of corresponding metal precursors by rapid injection of KBH₄.It turns out that of the catalytic activity of Rh₅Ni₉₅ BNPs showed higher catalytic activity of about 13010 mol-H₂×h^-1×mol-Rh^-1 for the hydrolysis of an alkaline KBH₄.The reaction order of KBH₄ concentration to Rh₅Ni₉₅ BNPs were determined to be 0.71 with a low apparent activation energy of 59.6±5.7 kJ/mol in the present experiments.（4）A series of ISOBAM-104 protected alloy structured Rh/Co BNPs were synthesized by co-reduction of corresponding metal precursors by rapid injection of KBH₄.The catalytic activity of Rh/Ni BNPs showed higher catalytic activity than monometallic Rh nanoparticles.And Rh₂₀Co₈₀ BNPs showed higher catalytic activityof about 13010 mol-H₂×h^-1×mol-Rh^-1 for the hydrolysis of an alkaline KBH₄.（5）A series of ISOBAM-104 protected alloyed structured Ag/Pt BNPs were synthesized by co-reduction of corresponding metal precursors by rapid injection of KBH₄.The as-prepared Pt MNPs with R_ISOBAM^-104 of 40 showed catalytic activity of about 9300 mol-H₂×h^-1×mol-Pt^-1.And all the Ag/Pt BNPs exhibited lower catalytic activity than Pt MNPs.