Enhanced Formic Acid Electrooxidation on Carbon Nanotube-Supported Pdm (M = Ag, Ni, Pt, Zn) Bimetallic Catalysts For Direct Formic Acid Fuel Cells

Abstract

Direct formic acid fuel cells (DFAFCs) are regarded as attractive power sources for portable devices and other small-scale energy applications. Palladium (Pd) is intrinsically highly active toward this reaction; however, monometallic Pd nanoparticles gradually lose their activity with time. This drawback can be mitigated by forming Pd-based alloys with secondary metals, which improves both stability and performance. Herein, carbon nanotube (CNT)-supported PdAg, PdNi, PdPt and PdZn catalysts were prepared via a NaBH4 sequential reduction method to investigate their formic acid electrooxidation (FAEO) behavior. Inductively coupled plasma mass spectrometry (ICP–MS) was used to determine the elemental composition of the catalyst, and transmission electron microscopy (TEM) analysis was used to determine the morphological structure. Electrochemical techniques including cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) were employed to assess and compare their FAEO performance. A current density of 16.65 mA/cm2 was achieved with PdNi/CNT at a potential of approximately 0.2 V. This is the result of a 1000 s CA analysis. Among the bimetallic catalysts, PdNi/CNT exhibited the highest activity and durability, combining a relatively large electrochemically active surface area with the lowest charge-transfer resistance and the most stable chronoamperometric response, thereby standing out as the most promising DFAFC anode catalyst.