Enhanced Performance of Sn@Pt Core-Shell Nanocatalysts Supported on Two Different Carbon Structures for the Hydrogen Oxidation Reaction in Acid Media

Sn@Pt core-shell nanocatalysts, supported on Vulcan XC-72 and home-developed nitrogen-doped graphene (Sn@Pt/C and Sn@Pt/NG, respectively), were evaluated for the hydrogen oxidation reaction (HOR) in acid electrolyte. The nanocatalysts were synthesized by the bromide anion exchange (BAE) method. TEM characterization confirmed the nanosize nature of Sn@Pt/C and Sn@Pt/NG, with an average particle size of 2.1 and 2.3 nm, respectively. Sn@Pt/C delivered a similar mass limiting current density (jl, m) of the HOR compared to Sn@Pt/NG, which was higher than those of Pt/C and Pt/NG (ca. 2 and 2.3-fold increase, respectively). Moreover, the Sn@Pt/C and Sn@Pt/NG core-shell nanocatalysts demonstrated a higher specific activity related to Pt/C and Pt/NG. Mass and specific Tafel slopes further demonstrated the improved catalytic activity of Sn@Pt/C for the HOR, followed by Sn@Pt/NG. The application of the nanocatalysts was proposed for polymer electrolyte membrane fuel cells (PEMFC).

Green Power Generation by Microbial Fuel Cells Using Pharmaceutical Wastewater as Substrate and Electroactive Biofilms (Bacteria/Biocarbon)

In this work, electroactive biofilms of Bacillus subtilis (B. subtilis) or Escherichia coli (E. coli) were supported on functionalized biocarbon (AB7-F), which was synthesized from waste leather and was used as catalysts to develop bioanodes for microbial fuel cells (MFCs). This way, bioanodes were fabricated and further evaluated in a three-electrode cell using pharmaceutical wastewater (PWW) as substrate. The electrochemical measurements showed a higher performance of the bioanode based on AB7-f+ B. subtilis to oxidize organic matter from PWW. The polarization curves in the dual-chamber MFC showed that AB7-f+ B. subtilis bioanode can generate an open circuit voltage of 602 mV and a power density of 77 mW m−2. During long-term tests of the MFC, a variation in performance was observed, with a maximum of 96.3 mW m−2 on day 7. Such variation was attributed to the development of more stable biofilm as well as consumption of some compounds metabolized by bacteria grown on the bioanode. The results showed that AB7-f+ B. subtilis can be used as bioanode for MFCs with PWW as substrate removing around 45% of the chemical oxygen demand (COD).