Carbon-Supported Pt-Based Quaternary Alloy Nanocatalysts for the Selective Electro-Oxidation of Glycerol

The selective electrocatalytic conversion of glycerol into value-added products provides a sustainable and efficient strategy for addressing the surplus of biomass-derived waste generated from the biodiesel production. In this paper, a series of carbon-supported PtPdRhRu quaternary alloy nanocatalysts (PtPdRhRu/C) with different atomic ratios (Equi, Pt-rich, Pd-rich, Rh-rich and Ru-rich) were prepared via a one-pot polyol method. The effects of these atomic ratios on the catalytic performance and the selectivity of the glycerol conversion to high-value products were investigated. The as-prepared PtPdRhRu/C nanocatalysts all possess a single-phase face-centered cubic (fcc) structure. Specifically, their mass activities are 10.5, 9.4, 8.1, 1.9 and 6.4 times higher than that of commercial Pt/C (20 wt%) for the Pt-rich, equimolar, Pd-rich, Rh-rich, and Ru-rich catalysts, respectively. This enhancement is suggested to be associated with the unique electronic modulation and synergistic effects inherent in the multicomponent surface. The Pd-rich catalyst exhibits a selectivity of 72% for glyceraldehyde, while the Rh-rich catalyst shows 53% selectivity for oxalic acid. The C2/C3 product ratio for the Rh-rich catalyst reaches 1.13, compared to 0.82 for the Ru-rich catalyst, suggesting that the presence of Rh and Ru atoms promotes C-C bond cleavage. In contrast, the C2/C3 ratios of the Pt-rich and Pd-rich catalysts are relatively low; notably, the C2/C3 ratio of the Pd-rich catalyst is only 0.20. This implies that the inclusion of Pt and Pd elements in the quaternary alloy is more conductive to the retention of C3 frameworks. These findings highlight the PtPdRhRu platform as a versatile framework for tuning the geometric and electronic environment of catalysts, providing a strategic approach for the selective electro-conversion of complex polyols.