Development of enhanced materials for direct-methanol fuel cell by combinatorial method and nanoscience

Emerging beyond-graphene elemental 2D materials for energy and catalysis applications

Elemental two-dimensional (2D) materials have emerged as promising candidates for energy and catalysis applications due to their unique physical, chemical, and electronic properties. These materials are advantageous in offering massive surface-to-volume ratios, favorable transport properties, intriguing physicochemical properties, and confinement effects resulting from the 2D ultrathin structure. In this review, we focus on the recent advances in emerging energy and catalysis applications based on beyond-graphene elemental 2D materials. First, we briefly introduce the general classification, structure, and properties of elemental 2D materials and the new advances in material preparation. We then discuss various applications in energy harvesting and storage, including solar cells, piezoelectric and triboelectric nanogenerators, thermoelectric devices, batteries, and supercapacitors. We further discuss the explorations of beyond-graphene elemental 2D materials for electrocatalysis, photocatalysis, and heterogeneous catalysis. Finally, the challenges and perspectives for the future development of elemental 2D materials in energy and catalysis are discussed.

Ternary PtFeCo alloys on graphene with high electrocatalytic activities for methanol oxidation

Ternary PtFeCo alloys as alternatives to conventional Pt electrocatalysts are highly important in the field of the methanol oxidation reaction. In this study, we demonstrate a one-pot two-step reduction method for the synthesis of graphene supported PtFeCo alloy nanocomposites as an integrated binder-free catalyst. The synergistic effect of alloying with Fe and Co as well as graphene decorating contributes to an increase in the utilization of the noble metal, namely, reducing the amount of Pt in the nanocomposites to 7%. After tailoring the elemental composition of the alloys, Pt₅₂Fe₂₉Co₁₉@G-7% exhibits a mass activity/specific activity of 1758.2 mA mg^-1_Pt/3.42 mA cm^-2 that is 3.13/3.45 times that of commercial Pt/C in an acidic medium. Impressively, it showed a superior mass current density of 9356.1 mA mg^-1_Pt at 60 °C which is close to the operating temperature of direct methanol fuel cells. Moreover, the as-obtained Pt₅₂Fe₂₉Co₁₉@G-7% also exhibited excellent CO tolerance and reliable stability compared to commercial Pt/C. The structural characterization further verifies that the surface strain and electronic effect play a critical role in determining the electrocatalytic properties of PtFeCo@G nanocomposites for the methanol oxidation reaction.

Combinatorial high-throughput screening for highly active Pd-Ir-Ce based ternary catalysts in electrochemical oxygen reduction reaction

A combinatorial library having 66 different ternary compositions of Pd-Ir-Ce was prepared via the impregnation method to find the optimum ternary composition with the highest performance toward oxygen reduction reaction (ORR) in acid media. Its performance in ORR activity of the combinatorial array was evaluated through two different combinatorial high-throughput screening methods to gain validity: (1) multielectrode half-cell method and (2) optical screening method. From the combinatorial results, the spot at 79:12:9 for Pd-Ir-Ce (at. %) in the array showed the highest ORR activity. The electrochemical characterizations of the single catalyst demonstrates that the optimized Pd79Ir12Ce9/C catalyst shows 1.5 times the ORR activity compared to that of Pd/C catalyst at 0.85 V (vs. RHE). In the Pd-Ir-Ce based catalysts, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results reveal that Ir and Ce are present in the form of IrO2 and CeO2, respectively, and the electron configuration of Pd is effectively modified through the decoration with IrO2 and CeO2. From the results, we suggest that the electro-modification of Pd through strong metal-metal oxide interaction with IrO2-CeO2 was a reason for the enhanced ORR activity.