Highly Active Pt-Fe Catalysts Towards CO Preferential Oxidation with an Ultra-Wide Temperature Window

Preferential oxidation of CO in H₂ (CO-PROX) is a promising solution to remove the residual CO in the feed stream to avoid Pt poisoning in proton-exchange-membrane fuel cells (PEMFCs), 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 MgAlO_x (denoted as MA) derived from PtFeMgAl-layered double hydroxides (PtFeMgAl-LDHs) precursor, which is featured with abundant Pt^{δ +}-(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°C-225 °C) at a rather high space velocity (130 000 mL g_cat ^-1 h^-1). The mass-specific activity reaches to 9.09 mol_CO g_Pt ^-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 Pt^{δ +}-(OH)_x-Fe³⁺ interfacial site is easily bound to the linearly-adsorbed CO at the adjacent Pt^{δ +} 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. A structure design strategy of interfacial synergistic catalysis towards CO-PROX is proposed in this work, which shows fundamental significance and application prospects in hydrogen purification.