Combinatorial PtSnM (M = Fe, Ni, Ru and Pd) nanoparticle catalyst library toward ethanol electrooxidation

Electrode arrays containing 91 combinations of Pt-Sn-M (M = Fe, Ni, Pd, and Ru) were prepared by borohydride reduction of aqueous metal salts on carbon paper, and screened by fluorescence assay for activity as ethanol electrooxidation catalysts. Catalysts that showed high activity for this reaction were identified as being Pt(80)Sn(10)Fe(10), Pt(80)Sn(10)Ni(10), Pt(70)Sn(20)Pd(10), and Pt(70)Sn(10)Ru(20) (numbers in parenthesis indicate atomic percent). These were significantly more active than Pt or PtSn catalysts, also present in the electrode arrays. These 4 compositions were synthesized as nanoparticles and characterized physically and electrochemically. X-ray diffraction showed a Pt face-centered cubic (fcc) structure with an average crystallite size of about 2.0 nm for all catalysts. The electrochemical tests for the oxidation of ethanol revealed excellent electrocatalytic activity and single cell (fuel cell) power density for all four catalyst formulations. Fe-containing catalysts exhibited the highest activity (13 A gPt−1) and single-cell performance (50 mW cm−2) followed by Ni- and Pd-containing materials with similar results; electrocatalytic activity around 10 A gPt−1 and power densities of 43 mW cm−2. The lowest performance was observed for the Ru-containing catalyst. However, its single-cell performance (30 mW cm−2) was still comparable to that of the commercial PtSn-Etek electrocatalyst. [Display omitted] •We applied combinatorial electrochemistry to discover promising catalyst toward ethanol electrooxidation.•Combinatorial method promotes an easy way to reduce cost when searching for better-performing materials.•66 PtSn-M/C (M = Ni, Ru, Rh and Fe) library was screened by fluorescence assay.•Single cell test confirms the combinatorial electrochemistry results.•PtSnFe/C composition furnished the highest activity towards ethanol electrooxidation (50 mW cm−2).