Direct liquid fuel cells represent one of the most rapidly emerging energy conversion devices. The main challenge in developing fuel cell devices is finding low-cost and highly active catalysts. In this work, PET bottle waste was transformed into nitrogen-doped graphene (NG) as valuable catalyst support. NG was prepared by a one-pot thermal decomposition process of mineral water waste bottles with urea at 800 °C. Then, NG/Pt electrocatalysts with Pt loadings as low as 0.9 wt.% and 1.8 wt.% were prepared via a simple reduction method in aqueous solution at room temperature. The physical and electrochemical properties of the NG/Pt electrocatalysts are characterized and evaluated for application in direct borohydride peroxide fuel cells (DBPFCs). The results show that NG/Pt catalysts display catalytic activity for borohydride oxidation reaction, particularly the NG/Pt_1, with a number of exchanged electrons of 2.7. Using NG/Pt composite in fuel cells is anticipated to lower prices and boost the usage of electrochemical energy devices. A DBPFC fuel cell using NG/Pt_1 catalyst (1.8 wt.% Pt) in the anode achieved a power density of 75 mW cm⁻² at 45 °C. The exceptional performance and economic viability become even more evident when expressed as mass-specific power density, reaching a value as high as 15.8 W mg_Pt⁻¹.

The synthesis of palladium-based trimetallic catalysts via a facile and scalable synthesis procedure was shown to yield highly promising materials for borohydride-based fuel cells, which are attractive for use in compact environments. This, thereby, provides a route to more environmentally friendly energy storage and generation systems. Carbon-supported trimetallic catalysts were herein prepared by three different routes: using a NaBH₄-ethylene glycol complex (PdAuNi/C_SBEG), a NaBH₄-2-propanol complex (PdAuNi/C_SBIPA), and a three-step route (PdAuNi/C_3-step). Notably, PdAuNi/C_SBIPA yielded highly dispersed trimetallic alloy particles, as determined by XRD, EDX, ICP-OES, XPS, and TEM. The activity of the catalysts for borohydride oxidation reaction was assessed by cyclic voltammetry and RDE-based procedures, with results referenced to a Pd/C catalyst. A number of exchanged electrons close to eight was obtained for PdAuNi/C_3-step and PdAuNi/C_SBIPA (7.4 and 7.1, respectively), while the others, PdAuNi/C_SBEG and Pd/C_SBIPA, presented lower values, 2.8 and 1.2, respectively. A direct borohydride-peroxide fuel cell employing PdAuNi/C_SBIPA catalyst in the anode attained a power density of 47.5 mW cm⁻² at room temperature, while the elevation of temperature to 75 °C led to an approximately four-fold increase in power density to 175 mW cm⁻². Trimetallic catalysts prepared via this synthesis route have significant potential for future development.