PtNb Deposited on High Surface Area Carbon Support as Catalyst for Ethanol Electroxidation

Abstract

Platinum-niobium catalysts have been proposed as alternative catalysts for ethanol electro-oxidation. Catalysts prepared by a combined alcohol-sodium borohydride reduction method showed crystal sizes in the range of 3-4 nm, with large amounts of niobium oxide, as TPR results confirmed. Platinum decorated on a mixture of Nb2O5 (amorphous and crystalline)/Vulcan XC-72R carbon black was also prepared , with similar crystal sizes. XANES region analyses showed a certain electronic effect in the case of the co-reduction of the two metals, in which a slight alloy fraction was detected. CO stripping results displayed a promising performance of the PtNb/C catalyst, with a small onset potential and a large current density for CO oxidation. Ethanol oxidation tests demonstrated a larger specific activity for the PtNb2O5 (crystalline)/C compared to the other catalysts. Furthermore, a large efficiency for ethanol oxidation was obtained for this platinum-niobium catalyst.

High-Temperature Synthesis of Small-Sized Pt/Nb Alloy Catalysts on Carbon Supports for Hydrothermal Reactions

“…By the Debye–Scherer equation based on the full-width at half-maximum of the PXRD patterns, the average particle sizes were estimated to be 3.6, 2.4, and 4.3 nm for Pt 3 Nb/BP2000, PtNb/BP2000, and Pt/BP2000, respectively, which indicated that metal aggregation under high temperatures could be suppressed by alloying. − We noted that the crystalline Nb 2 O 5 phase was obtained when only NbCl 5 was used with an identical high-temperature H 2 reduction (Figure S1b). This result indicates that Pt played a crucial role in Nb reduction probably by the H 2 spillover effect, , which was confirmed by H 2 -temperature-programmed-reduction (TPR) tests (Figure S2).…”

“…32−34 We noted that the crystalline Nb 2 O 5 phase was obtained when only NbCl 5 was used with an identical high-temperature H 2 reduction (Figure S1b). This result indicates that Pt played a crucial role in Nb reduction probably by the H 2 spillover effect, 26,35 which was confirmed by H 2 -temperature-programmed-reduction (TPR) tests (Figure S2). High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) observations showed that the metal nanoparticles were homogeneously dispersed over the whole C support without any large nanoparticles (Figure 1b).…”

“…Nevertheless, alloying with Nb is thermodynamically unfavorable because the extreme O affinity and very negative reduction potential of Nb restrict the reduction of Nb precursors to the metallic state. Although some efforts have been devoted to synthesizing Pt/Nb bimetallic catalysts, in most cases the prepared catalysts were actually the Pt nanoparticles supported on niobium oxide (NbO x ) or the composites of a Pt/Nb alloy and NbO x . − …”