Highly-Active Pt-Fe Catalysts towards CO Preferential Oxidation with an Ultra-wide Temperature Window

Abstract

Preferential oxidation of CO in H2 is a promising solution to remove residual CO in feed stream to avoid Pt poisoning in proton-exchange-membrane fuel cells, in which the development of high-efficiency catalysts with a wide temperature window remains a great challenge. Herein, we report a Fe(OH)x modified Pt clusters (~1.6 nm) catalyst supported on MgAlOx derived from PtFeMgAl-layered double hydroxides precursor, which is featured with abundant Ptδ+–(OH)x–Fe3+ interfacial sites. Impressively, the optimal catalyst Pt-Fe(OH)x/MA exhibits exceptional catalytic performance towards CO-PROX, which can completely remove CO in a H2-rich stream with an ultra-wide full CO conversion window (25−225 °C) at a rather high space velocity (130000 mL gcat−1 h−1). The mass-specific activity reaches to 9.09 molCO gPt−1 h−1 at 25 °C, which is preponderant to the state-of-the-art catalysts. In addition, a 240-h stream-on-line test over Pt-Fe(OH)x/MA shows a satisfactory stability. A comprehensive investigation based on in situ experimental studies and theoretical calculations reveals that the –OH group at the Ptδ+–(OH)x–Fe3+ interfacial site is easily bound to the linearly-adsorbed CO at the adjacent Ptδ+ site to form carboxylate intermediate, followed by its decomposition to CO2. Meanwhile, the generated coordination unsaturated Fe2+ site facilitates the activation cracking of O2 molecule without energy barrier.