Superior Formic Acid Electrooxidation Activity on Carbon Nanotube-Supported Binary Pd Nanocatalysts Prepared Via Sequential Sodium Borohydride Reduction Technique

Abstract

In this study, multiwalled carbon nanotube (MWCNT)-supported M (Pd, Ni, Co, Mn, V, Zn)/MWCNT monometallic and M (Ni, Co, Zn, V, Ag, Mn)@(Pd/MWCNT) binary nanocatalysts were investigated to examine the effect of second metal promotion to Pd on formic acid electrooxidation (FAEO) activity. The sequential sodium borohydride (SBH) reduction technique was used for the preparation of nanocatalysts. For binary nanocatalysts, first of all, the monometallic Pd/MWCNT nanocatalyst was prepared. Then, second metal precursors (NiCI2, CoCl2, ZnCI2, V2O5, AgNO3, and MnCI2) were added to Pd/MWCNT and further reduced with NaBH4. After filtration and drying, binary nanocatalysts M@(Pd/MWCNT) were obtained. X-ray diffractometry (XRD), inductively coupled plasma mass spectrometer (ICP-MS), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) methods were used to characterize the obtained nanocatalysts. In addition, cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) measurements were utilized to examine the electrochemical activities of the nanocatalysts for FAEO. The results indicate that Ni@(Pd/MWCNT) nanocatalyst is better than the other nanocatalysts with 10.75-mA cm(-2) specific and 2924.48-mA mg(-1) Pd mass activity. Furthermore, Ni@(Pd/MWCNT) nanocatalyst has 110.4-m(2) g(-1) electrochemical active surface area (ECSA). Consequently, it is clear that Ni@(Pd/MWCNT) nanocatalyst is a promising nanocatalyst for direct formic acid fuel cells (DFAFCs).