Low Pt loading with lattice strain for direct ethylene glycol fuel cells

Abstract

Low Pt loading electrodes are pivotal but challenging in direct ethylene glycol fuel cells (DEGFCs), necessitating a substantial enhancement in both the active site quantity and the catalytic capacity of Pt, which is a long-lasting contradiction in commonly used Pt alloy catalysts. Imparting a certain strain to Pt has been demonstrated to be effective in enhancing Pt activity, which is expected to resolve this bottleneck in alloy catalysts with high Pt weight fractions. However, conventional strain imposition strategies are disadvantageous under harsh conditions of high temperature and pressure as well as high facility requirements. Here, we activated Fe vacancies, induced the rearrangement of Pt atoms, and thereby successfully introduced compressive strain through an in situ facile one-step electrochemical process under ambient conditions. Consequently, the obtained Pt–Fe alloy catalyst (95.8 wt% Pt) achieved unprecedentedly high mass activity and specific activity in ethylene glycol oxidation (22.7 A mg_Pt⁻¹ and 23.4 mA cm_Pt⁻²). Of particular note is that the DEGFC achieves the highest power density and the best stability with a very low Pt loading electrode (Pt loading: 0.1 mg cm⁻²), surpassing all DEGFCs and many direct methanol fuel cells even with decent noble metal loading electrodes (noble metal loading: >1 mg cm⁻²) reported. Density-functional theory calculations demonstrate that Fe₃ vacancies prefer to adsorb Pt atoms mostly compared to other vacancies and atoms, leading to Pt redistribution and compressive strain. In situ FTIR and online mass spectrometry confirmed that the compression-strained Pt–Fe significantly improved the C–C bond cleavage efficiency and resistance to CO poisoning, revealing the intrinsic mechanism of its excellent performance.