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. 2023 Mar 16;13(6):1071.
doi: 10.3390/nano13061071.

WO3 Nanorods Decorated with Very Small Amount of Pt for Effective Hydrogen Evolution Reaction

Giacometta Mineo  1   2 , Luca Bruno  1   2 , Elena Bruno  1   2 , Salvo Mirabella  1   2
Affiliations

WO3 Nanorods Decorated with Very Small Amount of Pt for Effective Hydrogen Evolution Reaction

Giacometta Mineo et al. Nanomaterials (Basel). .

Abstract

The electrochemical hydrogen evolution reaction (HER) is one of the most promising green methods for the efficient production of renewable and sustainable H2, for which platinum possesses the highest catalytic activity. Cost-effective alternatives can be obtained by reducing the Pt amount and still preserving its activity. The Pt nanoparticle decoration of suitable current collectors can be effectively realized by using transition metal oxide (TMO) nanostructures. Among them, WO3 nanorods are the most eligible option, thanks to their high stability in acidic environments, and large availability. Herein, a simple and affordable hydrothermal route is used for the synthesis of hexagonal WO3 nanorods (average length and diameter of 400 and 50 nm, respectively), whose crystal structure is modified after annealing at 400 °C for 60 min, to obtain a mixed hexagonal/monoclinic crystal structure. These nanostructures were investigated as support for the ultra-low-Pt nanoparticles (0.2-1.13 μg/cm2): decoration occurs by drop casting some drops of a Pt nanoparticle aqueous solution and the electrodes were tested for the HER in acidic environment. Pt-decorated WO3 nanorods were characterized by performing scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Rutherford backscattering spectrometry (RBS), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and chronopotentiometry. HER catalytic activity is studied as a function of the total Pt nanoparticle loading, thus obtaining an outstanding overpotential of 32 mV at 10 mA/cm2, a Tafel slope of 31 mV/dec, a turn-over frequency of 5 Hz at -15 mV, and a mass activity of 9 A/mg at 10 mA/cm2 for the sample decorated with the highest Pt amount (1.13 μg/cm2). These data show that WO3 nanorods act as excellent supports for the development of an ultra-low-Pt-amount-based cathode for efficient and low-cost electrochemical HER.

Keywords: WO3; electrochemistry; hydrogen evolution reaction; nanorods; ultra-low Pt amount.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) Tilted low-magnification SEM images of bare WO3 electrode, composed of 3D agglomeration of nanorods; (b) low-magnification SEM images of WO3 nanorods decorated with Pt nanoparticles (highlighted in orange circles); (c) RBS spectrum of Pt nanoparticles on a flat Si substrate for the 5Pt_WO3, the 10Pt_WO3, and the 20Pt_WO3 electrodes (blue, yellow, and green lines, respectively).
Figure 2
Figure 2
(a) LSV curves of the WO3, the 5Pt_WO3, the 10Pt_WO3, and the 20Pt_WO3 electrodes (red, blue, yellow, and green lines, respectively); (b) current density at −0.09 V as a function of Pt dose of the 5Pt_WO3, the 10Pt_WO3, and the 20Pt_WO3 electrodes; (c) Tafel plot and liner fit of WO3, 5Pt_WO3, the 10Pt_WO3, and the 20Pt_WO3 electrodes (red, blue, yellow, and green circles and lines, respectively).
Figure 3
Figure 3
(a) TOF of the 5Pt_WO3, the 10Pt_WO3, and the 20Pt_WO3 electrodes (red, blue, yellow, and green circles, respectively) as a function of the overpotential; (b) comparison between the mass activity of the Pt-based electrodes reported in the literature (blue balls) [6] and our Pt-decorated WO3 electrodes (red balls); (c) chronopotentiometry analysis of the 20Pt_WO3 electrode.
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