Exceptional performance of gold supported on fluoridated hydroxyapatite catalysts in CO-cleanup of H2-rich stream: High activity and resistance under PEMFC operation conditions

Abstract

• A novel Au/F(x)-HAP catalyst formulation with different amounts of F was investigated for the COPROX process. • Significant changes in the chemical, textural and structural properties were observed on the partially fluorinated catalysts. • The reduced catalysts comprised relatively small Au particle sizes (< 5 nm). • The HAP modification with F affects its proton conductivity and the electronic properties of the Au particles. • The optimized COPROX catalyst proves to be able to eliminate CO completely under realistic COPROX conditions. Proton-exchange-membrane fuel cells (PEMFCs) appear to be the most promising solution for future automotive applications. Facing the lack of efficient hydrogen storage and transportation solutions, current research is focused on the development of on-board catalytic reformers. In this strategy, the purity of hydrogen stream is still an unresolved issue that needs to be addressed in order to avoid poisoning of the Pt electrodes of PEMFC. Here we report the extraordinary performance of gold supported on fluorine-substituted hydroxyapatite (HAP) catalysts in the CO preferential oxidation (COPROX) process. At 80 °C, the optimized catalyst (Au/F-(1)) proves to be highly active, selective (showing a CO conversion (X CO ) of 100 % and selectivity towards CO 2 production (S CO2 ) close to 62 %) and very resistant to deactivation, even in the presence of H 2 O (15 %) and CO 2 (20 %). In addition, these results were obtained at relatively high weight hourly space velocity (WHSV: 60,000 cm 3 g −1 h −1 ). It should be highlighted that our catalysts clearly outperform state-of-the-art gold catalysts. Our discovery introduces Au/F(x)-HAP catalysts as a viable solution for an effective elimination of CO to feed PEMFCs with CO-free hydrogen streams.

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