Palladium‐Based Bimetallic Nanocrystal Catalysts for the Direct Synthesis of Hydrogen Peroxide

Abstract

The direct synthesis of H2O2 from H2 and O2 is a strongly desired reaction for green processes and a promising alternative to the commercialized anthraquinone process. The design of efficient catalysts with high activity and H2O2 selectivity is highly desirable and yet challenging. Metal dopants enhance the performance of the active phase by increasing reaction rates, stability, and/or selectivity. The identification of efficient dopants relies mostly on catalysts prepared with a random and non‐uniform deposition of active and promoter phases. To study the promotional effects of metal doping on Pd catalysts, we employ colloidal, bimetallic nanocrystals (NCs) to produce catalysts in which the active and doping metals are colocalized to a fine extent. In the absence of any acid and halide promotors, PdSn and PdGa NCs supported on acid‐pretreated TiO2 (PdSn/s‐TiO2, PdGa/s‐TiO2) were highly efficient and outperformed the monometallic Pd catalyst (Pd/s‐TiO2), whereas in the presence of an acid promotor, the overall H2O2 productivity was also further enhanced for the Ni‐, Ga‐, In‐, and Sn‐doped catalysts with respect to Pd/s‐TiO2.

Dynamic structural changes of supported Pd, PdSn, and PdIn nanoparticles during continuous flow high pressure direct H2O2synthesis

“…Whereas previously catalysts were mostly tested in a narrow window of H 2 : O 2 ratios with excess of O 2 , 1,[10][11][12]14 in this work the H 2 : O 2 ratio was varied from 10 : 1 to 1 : 10 and it was found that trends in activity and stability of the catalysts strongly depend on the H 2 : O 2 ratio (Fig. 2).…”

“…† Detailed characterisation (TEM, EDX mapping, XRD, XAS) of the isolated unsupported bimetallic nanoparticles and the supported catalysts is reported in our recent publication. 14 TEM analysis reported in the cited work 14 reveals relatively broad NP size distribution between 2 and 6 nm with maxima at 3-4 nm.…”

“…9 Transmission electron microscopy TEM images with particle size distributions of the as-received catalysts are reported elsewhere. 14 The corresponding images of the studied catalysts after the operando measurements are shown in Fig. 10 Catalysis Science & Technology Paper small (≤1 nm) particles/clusters did not increase after H 2 O 2 synthesis experiments (compare Fig.…”

“…Mono-and bimetallic catalysts were synthesized by depositing Pd(M) nanoparticles on TiO 2 (Aeroxide® P25) pretreated with diluted H 2 SO 4 (denoted as s-TiO 2 ) as reported previously 13,14 to obtain Pd/s-TiO 2 (4.5 wt% Pd); PdSn/s-TiO 2 (4.1 wt% Pd and 2.8 wt% Sn); PdIn/s-TiO 2 (3.4 wt% Pd and 1.2 wt% In) catalysts. For convenience, the synthesis procedure is summarized in the ESI.…”

NaCl-template-based synthesis of TiO2-Pd/Pt hollow nanospheres for H2O2 direct synthesis and CO oxidation

“…The H 2 O 2 concentration was analyzed ex situ by UV-Vis spectroscopy. 16 Accordingly, the as-prepared TiO 2 -Pd HNS exhibit a H 2 O 2 selectivity of 47% with a productivity of 1850 mol kg Pd −1 h −1 (Fig. 5e and f ).…”