Graphical Heptanol oxidation : Melamine modification of commercial activated carbon can greatly tune the performance of Pt−Bi catalysts in n -heptanol oxidation. C 3 N 4 -modified AC favors the formation of PtBi alloy in comparison to N-doped AC, and consequently boosts the activity and selectivity to heptanoic acid. Different bimetallic platinum and bismuth catalysts supported on melamine-modified activated carbon (AC) are designed by a co-impregnation method. Through controlling the activation temperatures of the melamine−AC mixture, a series of N-doped and C 3 N 4 -modified AC (N−AC and C 3 N 4 −AC) are prepared. Combined powder X-ray diffractions, X-ray photoelectron spectroscopic, and high-angle annual dark-field scanning transmission electron microscopic studies demonstrate that the introduction of C 3 N 4 favors the formation of PtBi alloy and leads to increased particle sizes in comparison to the pristine and N-doped AC-supported bimetallics. The catalytic performance of the developed catalysts is evaluated in the oxidation of n -heptanol oxidation in a batch mode using O 2 as the oxidant. PtBi/C 3 N 4 −AC exhibits significantly boosted activity as well as selectivity to heptanoic acid as compared with the other catalysts. A high yield of heptanoic acid of 69 % can be achieved under the optimized reaction conditions. Furthermore, our work points to the PtBi alloy as the most active sites for the alcohol oxidation. Catalyst deactivation occurs in the cycling tests, mainly due to the collapse of the alloy phase and likely the decrease in particle sizes.
Nanostructured bimetallic Pt–Bi catalysts are designed by defect engineering of N-doped carbons as the hosts. The optimal catalyst delivers good yields (>98%) in the direct oxidation of C5–C9 linear α-alcohols to corresponding fatty acids, significantly outperforming activated carbon-supported benchmarks and rivaling the state-of-the-art systems. A combined kinetic and computational study on n-heptanol oxidation as a model reaction unveils the kinetic and thermodynamic origins of the better performance of the PtBi alloy than neat or Bi-modified Pt(111) surfaces. Structure–performance correlations further identify that the metal particle size, surface Bi/Pt ratio, and strong basicity strongly influence the catalyst performance in alcohol oxidation. The creation of nitrogen defects facilitates the formation of the surface PtBi alloy and brings strong basicity, accounting for the boosted performance. These findings enable a step closer toward the manufacture of valuable fatty acids from abundant coal by coupling the advanced oxidation with the recently piloted higher alcohol synthesis via the Co–Co2C-catalyzed Fischer–Tropsch reaction.
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