Bifunctional PdMoPt trimetallene boosts alcohol-water electrolysis

Abstract

Substituting oxygen evolution with alcohol oxidation is crucial for enhancing the cathodic hydrogen evolution reaction (HER) at low voltages. However, the development of high-performance bifunctional catalysts remains a challenge. In this study, an ultrathin and porous PdMoPt trimetallene is developed using a wet-chemical strategy. The synergetic effect between alloying metals regulates the adsorption energy of reaction intermediates, resulting in exceptional activity and stability for the electrooxidation of various alcohols. Specifically, the mass activity of PdMoPt trimetallene toward the electrooxidation of methanol, ethylene glycol, and glycerol reaches 6.13, 5.5, and 4.37 A mg_Pd+Pt ^-1, respectively. Moreover, the catalyst demonstrates outstanding HER activity, requiring only a 39 mV overpotential to achieve 10 mA cm^-2. By employing PdMoPt trimetallene as both the anode and cathode catalyst, we established an alcohol-water hybrid electrolysis system, significantly reducing the voltage requirements for hydrogen production. This work presents a promising avenue for the development of bifunctional catalysts for energy-efficient hydrogen production.

Fig. 1. Preparation and characterization of PdMoPt trimetallene. (a) Schematic illustration of the synthesis of PdMoPt trimetallene. (b) TEM micrograph of PdMoPt trimetallene and (c) magnified details of the yellow square area. (d) HAADF-STEM micrograph of PdMoPt trimetallene and (e) magnified details of the orange square area. (f) Representative HRTEM images of a PdMoPt trimetallene sheet, and (g) magnified view of its yellow square area and (h) the magnified view of the orange square area. (i) AC HAADF-STEM image of a representative PdMoPt trimetallene. (j) STEM image and corresponding elemental mappings of PdMoPt trimetallene.

Fig. 2. MOR performance. (a) CV curves of the catalysts in a 1 M KOH solution. (b) CV curves of the catalysts normalized to the loading amounts of Pd and Pt in a 1 M KOH with 1 M methanol solution. (c) CV curves of the catalysts normalized to ECSA in a 1 M KOH with 1 M methanol solution. (d) Comparison of specific and mass activities of the catalysts. (e) CA curves of the catalysts in a 1 M KOH with 1 M methanol solution. (f) CA curves of the catalysts with CV reactivation every 1000 s. (g) The calculated MOR free-energy profiles. (h) ΔG_CO* on the surfaces of Pd, PdMo, and PdMoPt.

Fig. 3. EGOR and GOR performance. (a) CV curves of the catalysts in a 1 M KOH with 1 M ethylene glycol solution. (b) Comprehensive comparison of the catalysts for EGOR measurements. (c) CV curves of the catalysts in a 1 M KOH with 1 M glycerol solution. (d) Comprehensive comparison of the catalysts for GOR measurements.

Fig. 4. HER performance. (a) Polarization curves of the catalysts in a 1 M KOH solution. (b) Tafel plots of the catalysts for the HER. (c) Chronopotentiometric curves of the PdMoPt catalyst carried out in 1 M KOH with a constant current density of 10 and 100 mA cm⁻². (d) Calculated free energy diagram for hydrogen adsorption on the Pd, Pt, PdMo, and PdMoPt surfaces.

Fig. 5. Alcohol–water electrolysis performance. (a) Schematic diagram of an alcohol–water hybrid electrolyzer. (b) LSV curves of the cells equipped with PdMoPt as both anode and cathode catalysts in the AOR-HER based electrolyzer and equipped with IrO₂ as the anode and Pt/C as the cathode in alkaline solution. (c) Comparison of the cell voltage for Pt/C, PdMo and PdMoPt in the AOR-HER hybrid electrolyzers. (d) Comparison of recent electrolysis performances of catalysts for alcohol–water hybrid electrolyzers. (e) Chronopotentiometric curves of PdMoPt as both anode and cathode catalysts with a constant current density of 10 mA cm⁻² in the AOR-HER based electrolyzers. (f) HAADF-STEM and elemental mappings of the PdMoPt catalyst at the anode after the stability measurement. (g) HAADF-STEM and elemental mappings of the PdMoPt catalyst at the cathode after the stability measurement.