Mesoporous multimetallic nanospheres with exposed highly entropic alloy sites

Abstract

Multimetallic alloys (MMAs) with various compositions enrich the materials library with increasing diversity and have received much attention in catalysis applications. However, precisely shaping MMAs in mesoporous nanostructures and mapping the distributions of multiple elements remain big challenge due to the different reduction kinetics of various metal precursors and the complexity of crystal growth. Here we design a one-pot wet-chemical reduction approach to synthesize core-shell motif PtPdRhRuCu mesoporous nanospheres (PtPdRhRuCu MMNs) using a diblock copolymer as the soft template. The PtPdRhRuCu MMNs feature adjustable compositions and exposed porous structures rich in highly entropic alloy sites. The formation processes of the mesoporous structures and the reduction and growth kinetics of different metal precursors of PtPdRhRuCu MMNs are revealed. The PtPdRhRuCu MMNs exhibit robust electrocatalytic hydrogen evolution reaction (HER) activities and low overpotentials of 10, 13, and 28 mV at a current density of 10 mA cm^-2 in alkaline (1.0 M KOH), acidic (0.5 M H₂SO₄), and neutral (1.0 M phosphate buffer solution (PBS)) electrolytes, respectively. The accelerated kinetics of the HER in PtPdRhRuCu MMNs are derived from multiple compositions with synergistic interactions among various metal sites and mesoporous structures with excellent mass/electron transportation characteristics.

Fig. 1. Structural characterization of PtPdRhRuCu MMNs.

a Schematic illustration of the synthesis of PtPdRhRuCu MMNs. b SEM (scale bar: 100 nm), c HAADF–STEM (scale bar: 100 nm). Inset: The corresponding SAED pattern (scale bar: 5 nm⁻¹), d HRTEM (scale bar: 2 nm) (FFT patterns was shown inset), e atomic elemental mapping images (scale bar: 50 nm), f line-scanning results, g normalized atomic compositional profile, and h powder XRD pattern (compared to fcc Pt, PDF#04-0802) of the PtPdRhRuCu MMNs. Source data are provided as a Source data file.

Fig. 2. Elemental distributions at one pore of PtPdRhRuCu MMNs.

a HAADF–STEM image and EDS maps at one edge pore of a PtPdRhRuCu MMN (scale bar: 10 nm). b Corresponding ΔS_mix value at the selected area (i.e., 1, 2, 3, and 4) of (a). c Schematic of the elemental distribution around one mesopore of the PtPdRhRuCu MMN. Error bar in (b) correspond to the standard deviation based on the measurements at three points within the selected region. Source data are provided as a Source data file.

Fig. 3. Reduction process for PtPdRhRuCu MMNs.

a Time-dependent HAADF images (scale bars: 100 nm) and b composition distributions (determined by SEM‒EDS) of PtPdRhRuCu MMNs. c Schematic illustration of the formation of PtPdRhRuCu MMNs. Source data are provided as a Source data file.

Fig. 4. Electrochemical HER performance.

a HER polarization curves of PtPdRhRuCu MMNs, Pt MNs, and Pt/C in 1.0 M KOH electrolyte after manual iR correction. b Comparison of overpotentials required to achieve 10 mA cm⁻² and TOF values at an overpotential of 50 mV for PtPdRhRuCu MMNs and Pt MNs. Error bars correspond to the standard deviation of three independent experiments. c LSV curves before (solid lines) and after 10,000 CV cycles (dashed lines) for various catalysts in alkaline media. d Long-term stability tests of PtPdRhRuCu MMNs through the chronopotentiometry method at current densities from 10 to 100 mA cm⁻². e CV stability tests of PtPdRhRuCu MMNs in 0.5 M H₂SO₄ and 1.0 M PBS solutions. f Comparison of the overpotentials at 10 mA cm⁻² (η₁₀) with recently reported nanosized MMA and Pt-based HER catalysts in alkaline (1.0 M KOH), neutral (1.0 M PBS), and acidic media (0.5 M H₂SO₄), originating from Supplementary Tables 6, 7. LSV scan rate: 5 mV s⁻¹. Source data are provided as a Source data file.