Shaping Single-Crystalline Trimetallic Pt–Pd–Rh Nanocrystals toward High-Efficiency C–C Splitting of Ethanol in Conversion to CO₂

Abstract

Atomic-scale construction and high-throughput screening of robust multicomponent nanocatalysts with tunable well-defined surface structures and associated active sites for ethanol electro-oxidation reaction (EOR) in high activity and selectivity, referring to C−C bond cleavage and full oxidation of ethanol as a clean and sustainable energy source, has remained a great challenge. Herein, we demonstrate a powerful conceptual approach to design, synthesize and optimize single-crystalline Pt−Pd−Rh nanocrystals of altered shapes and compositions for enhanced EOR performance, based on combined density functional theory (DFT) calculations and experiment study. (111)-terminated Pt−Pd−Rh nano-truncated-octahedrons (NTOs) and (100)-terminated Pt−Pd−Rh nanocubes (NCs) with varied-compositions were prepared by regulating the reduction tendency of metal precursors in a facile hydrothermal method. Aided by DFT calculations, Pt3PdRh NTOs, PtPdRh NTO, and 8.8 nm PtPdRh NCs-200 were screened to be the best performing catalysts with the highest EOR activity (five times as much as that of commercial Pt black) at 0.5 V vs. NHE. Amongst these catalysts, PtPdRh NTOs exhibited the highest selectivity to CO2 at 0.5 V and the noteworthy capability to fully oxidize ethanol at extremely low potential (0.35 V); 8.8 nm PtPdRh NCs-200 possessed the best durability. Morphology and surface composition correlated to the synergistic effect of three metals were verified to affect the EOR performance of well-shaped Pt−Pd−Rh nanocrystals. Combined with in situ FTIR, it was deduced that appropriate surface composition and exposed facets were the key factors to the promoted capability in the cleavage of C−C bond down to low potential. Through adjusting surface composition and morphology of Pt−Pd−Rh nanocrystals with homogeneous element distribution, enhanced EOR performance was achieved in light of DFT simulations of the two elementary reactions (i.e., breakdown of C−C bond, and oxidation of COad). This work has offered an effective and useful strategy to promote the reactivity of multicomponent heterogeneous nanocatalysts with optimized compositions and surface structures for many industrial catalytic processes.

Recent Advances on Electro-Oxidation of Ethanol on Pt- and Pd-Based Catalysts: From Reaction Mechanisms to Catalytic Materials

“…These alloys also tend to promote the partial oxidation of acetaldehyde to acetic acid. However, catalysts with a bifunctional effect do not particularly enhance C-C bond cleavage during EOR [81].…”

“…Regardless of the media, Pt-based materials represent the benchmark catalysts for ethanol oxidation. Elements such as Ru [32,33,35,60,82,83], Sn [15,32,33,35,80,[84][85][86], Pb [21,[87][88][89][90][91], Bi [36,89,90,92,93], Re [86], Sb [93], Ir [94], Au [95], Ce [96], Rh [81,97], Pd [81,98,99], Fe [100], Ni [95,101], P [102], Mo [83,103] have been widely employed to enhance the activity and selectivity. In addition, metal oxides, such as MgO, CeO2, ZrO2, SnOx [76,94,104] RuO2, PbOx [88] have also been investigated for facilitating the removal of CO.…”

“…Bimetallic or ternary nanocrystals have also been studied to explore the optimal combination of higher activity surface facets and electronic effect. The composition-varied (100)-terminated Pt-Pd-Rh nanocubes (NCs) and (111)-terminated Pt-Pd-Rh nanotruncated-oxtahedrons (NTOs) were synthesized with the help of halides [81]. Owing to the synergistic effects resulted from appropriate surface composition and exposed facets, the Pt-Pd-Rh NTOs exhibited the highest selectivity to CO2 and PtPdRh NCs possessed the best durability.…”

Evolution of surface of Pd-Rh bimetallic nanocubes and its correlation with CO oxidation

“…S3, the peaks of Pd x Rh 1−x NCs XRD patterns shifted to low angles with the increase of Pd concentration, indicating a lattice expansion due to the incorporation of Pd into Rh. The detail shape-control synthesis mechanism of Pd-Rh NCs by halide ions has been discussed in our previous reports [40][41][42].…”

Ultrathin‐Polyaniline‐Coated Pt–Ni Alloy Nanooctahedra for the Electrochemical Methanol Oxidation Reaction

“…[5,6] Furthermore, inadequate activity and durability,w hich have been attributed to shape deformation and surface poisoning of Pt catalysts by strong adsorption of intermediate speciesd uring electrocatalytic reactions, are other significant issues that remaint ob eo vercome in terms of their application in PEMFCs. [7][8][9][10] To overcome these limitations, tremendous efforts have been devoted to developing highly active, durable, and lessexpensive Pt-based electrocatalysts. [11][12][13][14] Among variousadvances, alloying of Pt nanocrystals( NCs) with more abundant and less expensive transition metals (PtM) has been intensively investigated to reduce Pt loadings and improve electrocatalytic activity,s electivity,a nd durability for myriad reactions.…”