High-throughput, combinatorial synthesis of multimetallic nanoclusters

Abstract

Multimetallic nanoclusters (MMNCs) offer unique and tailorable surface chemistries that hold great potential for numerous catalytic applications. The efficient exploration of this vast chemical space necessitates an accelerated discovery pipeline that supersedes traditional "trial-and-error" experimentation while guaranteeing uniform microstructures despite compositional complexity. Herein, we report the high-throughput synthesis of an extensive series of ultrafine and homogeneous alloy MMNCs, achieved by 1) a flexible compositional design by formulation in the precursor solution phase and 2) the ultrafast synthesis of alloy MMNCs using thermal shock heating (i.e., ∼1,650 K, ∼500 ms). This approach is remarkably facile and easily accessible compared to conventional vapor-phase deposition, and the particle size and structural uniformity enable comparative studies across compositionally different MMNCs. Rapid electrochemical screening is demonstrated by using a scanning droplet cell, enabling us to discover two promising electrocatalysts, which we subsequently validated using a rotating disk setup. This demonstrated high-throughput material discovery pipeline presents a paradigm for facile and accelerated exploration of MMNCs for a broad range of applications.

Keywords: combinatorial; high-throughput synthesis; multimetallic nanoclusters; oxygen reduction reaction; thermal shock.

Fig. 1.

(A) Schematic of a vapor-phase deposition method. (B) The high-throughput synthesis of MMNCs. Step I: combinatorial composition design in the liquid phase and then deposition on carbon supports; step II: rapid thermal shock synthesis (∼1,650 K, 500 ms). (C) EDS maps of the ternary salt mixture containing Pt, Pd, and Rh on the carbon support, demonstrating the uniform precursor loading. (D–F) TEM images demonstrating the similar size distribution and dispersal density of the ternary (PtPdRh), quinary (PtPdRhRuIr), and octonary (PtPdRhRuIrFeCoNi) MMNCs. (G and H) MMNCs synthesized by thermal shock in comparison with literature values in terms of size distribution and dispersal density [red stars, thermal shock; black dots, probe lithography (10, 34); green dots, macromolecular template method (8)].

Fig. 2.

Combinatorial synthesis of MMNCs featuring a solid-solution structure. (A) Low-magnification HAADF and EDS maps of quinary MMNCs (PtPdRhRuIr), demonstrating the uniform distribution of each element across the CA-CNF support. (B–D) High-resolution HAADF images and EDS maps of ternary, quinary, and octonary MMNCs demonstrating the uniform/homogeneous distribution of each element within the resulting nanoclusters. (Scale bars: 5 nm.) (E) Powder XRD measurement for ternary, quinary, and octonary MMNCs, showing the single-phase FCC structure without obvious secondary phases. (F) The synchrotron XRD (λ = 0.2113 Å) profile of PtPdRh still exhibits a single-phase FCC structure, with a lattice constant of 3.87 Å. a.u., arbitrary units.

Fig. 3.

Scale-up synthesis and fast screening of MMNCs for electrocatalytic reactions. (A) Schematic illustration of the combinatorial and high-throughput synthesis of uniform MMNCs. (B) The scanning droplet cell setup and patterned samples on the copper substrate. CE, counter electrode; RE, reference electrode; WE, working electrode. (C) Fast screening of PtPd-based MMNCs for catalytic ORR (22 compositions + 1 blank, 0.1 M KOH, 5 mV/s scan rate). (D) The compositional designs and their corresponding ORR performances presented in a neural network diagram. The size of the circles represents the magnitude of the specific current at 0.45 V for ORR. (E) Synchrotron XRD profiles for PtPdRhNi and PtPdFeCoNi, showing the single-phase FCC structure. a.u., arbitrary units. (F and G) TEM image (F) and elemental maps (G) of PtPdFeCoNi with uniform small size and alloy structure. F, Inset is a high-resolution TEM image of PtPdFeCoNi. (Scale bar: 5 nm.)

Fig. 4.

Electrochemical analysis of PtPdRhNi, PtPdFeCoNi, and a control Pt catalyst for ORR. (A) Cycle voltammograms of the three samples, where they show a clear ORR peak at ∼0.8 V (scan rate: 10 mV/s). (B) Linear-sweep voltammograms of the three samples (rotation rate: 1,600 rpm; scan rate: 10 mV/s). Both MMNCs outperform the Pt control sample with a higher current at given potentials. (C) Tafel analysis of the three samples, displaying similar reaction kinetics for the three samples. (D) Stability test for the three samples by holding the potential at 0.6 V (vs. RHE, rotation rate: 900 rpm), in which the three samples show relative stability after an initial decay.