Nano high-entropy oxide cathode with enhanced stability for direct borohydride fuel cells

• Published in: Journal of energy chemistry 2025-01, Vol.100, p.309-316
• Main Authors: Zhang, Lei, Kuang, Lingfeng, Zhang, Lianke, Chu, Wen, Qin, Haiying, Zhang, Jing, He, Junjing, Ni, Hualiang, Chi, Hongzhong
• Format: Article
• Language: English
• Subjects: Carbothermal shock; Direct borohydride fuel cells; High-entropy oxides; Oxygen reduction reaction; Stability
• ISSN: 2095-4956
• DOI: 10.1016/j.jechem.2024.08.055

The prepared (PtFeCoNiCu)O/C, with particle sizes ranging from 2 to 4 nm, exhibits superior catalytic stability. [Display omitted] •Ultrafine carbon-loaded nano-high-entropy oxide (PtFeCoNiCu)O/C is synthesized.•(PtFeCoNiCu)O/C has high selectivity for 4-electron reaction pathways with 3.94 transferred electrons.•(PtFeCoNiCu)O/C exhibits superior durability towards ORR with 3 mV positive shift after 40 k cycles.•A DBFC using (PtFeCoNiCu)O/C cathode achieves a maximum power density of 441 mW cm−2 at 60℃. High-entropy materials have become high-activity electrocatalysis owing to their high-entropy effect and multiple active sites. Herein, we synthesize a series of carbon-supported nano high-entropy oxides (HEOs/C), specifically (PtFeCoNiCu)O/C, using a carbothermal shock (CTS) method for application as a cathode catalyst in direct borohydride fuel cells (DBFCs). The microstructure of the prepared catalysts was characterized by X-ray photoelectron spectroscopy, X-ray absorption fine structure, and transmission electron microscopy. The prepared (PtFeCoNiCu)O/C, with particle sizes ranging from 2 to 4 nm, demonstrates 3.94 transferred electrons towards the oxygen reduction reaction in an alkaline environment, resulting in a minimal H2O2 yield of 2.6%. Additionally, it exhibits a Tafel slope of 61 mV dec−1, surpassing that of commercial Pt/C (82 mV dec−1). Furthermore, after 40,000 cycles of cyclic voltammetry (CV) testing, the half-wave potential of (PtFeCoNiCu)O/C shows a positive shift of 3 mV, with no notable decline in the limiting current density. When (PtFeCoNiCu)O/C is used as a cathode catalyst in DBFCs, the DBFC achieves a maximum power density of 441 mW cm−2 at 60 °C and sustains a cell voltage of approximately 0.73 V after 52 h at 30 °C. These findings confirm that HEO/C is a promising cathode catalyst for DBFCs.