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Proton exchange membrane fuel cells suffer from performance degradation caused by the oxidation and corrosion of carbon supports. Metal–platinum interactions can enhance the catalytic activity and stability due to compositional and geometric effects. Two-dimensional MXenes have been intensively studied in recent years and are expanding rapidly in both types and applications. Recently, ORR performances of dual-transition metal MXenes with abundant surface Mo vacancy have been demonstrated as efficient electrocatalysts toward oxygen reduction reaction in an alkaline solution. In this study, the electrochemical performances of Mo-based MXenes-supported Pt electrocatalysts toward oxygen reduction reaction are investigated in an acidic solution. Compared with the Pt/C catalysts, Pt/Mo2TiC2Fx exhibits improved durability, with a 28.7 mV negative shift of the half-wave potential after continuous scanning of 5000 cycles, which is superior to Pt/C with an 84.3 mV negative shift. The proton-exchange membrane fuel cell with Pt/Mo2TiC2Fx as the cathode catalyst also shows excellent activity and stability with a 0.7% potential fade after 9 h. According to the morphology evolution during oxygen reduction, the excellence in electrochemistry is due to the coherent interface between Pt and MXene, which provides a high binding force between Pt nanoparticles and the supporting materials. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide production through the electrochemical two-electron oxygen reduction presents a compelling alternative to the anthraquinone process due to the cheap starting materials and low operating temperature and pressure. Transition metal species featuring with multi-active sites, offer high electrochemical activity and selectivity. MXenes, distinguished by excellent electrical conductivity and the two-dimensional structure facilitating smooth ion transportation, further enhance the prospects of this production approach. In this study, three Mo-based MXenes were synthesized: Mo 2 TiC 2 F x , Mo 2 Ti 2 C 3 F x and Mo 2 CF x. Among these, Mo 2 TiC 2 F x emerged as the most promising catalyst for 2e−ORR, achieving a remarkable H 2 O 2 yield of up to 0.54 mol·g cat −1·h−1. Moreover, it also exhibits a high H 2 O 2 selectivity ranging from 81.3 % at 0.2 V to 94.1 % at 0.6 V vs. RHE, coupled with an impressive faradaic efficiency of 76.4 % at 0.4 V using H-cell. Further analysis indicates that the superior 2e−ORR performance can be attributed to the presence of metallic Mo on the surface of Mo 2 TiC 2 F x. [ABSTRACT FROM AUTHOR]

The production of H 2 O 2 by oxygen reduction reaction (ORR) is low energy consumption and environmentally friendly. Pd/C is an effective electrocatalyst for oxygen reduction, while its selectivity is low due to a tendentious four-electron pathway ORR process. The limited reserves of palladium and inevitable corrosion issue of carbon support add extra obstacles toward practical application. In this work, Pd nanoparticles with 3–5 nm were synthesized on MXene sheets. Results indicated that Pd/MXene exhibited 3.5∼4.2 times ring current than Pd/C and much higher H 2 O 2 selectivity. The H 2 O 2 yield of Pd/MXene was measured to be 1.43 mol g−1 h−1. The excellence in electrochemistry was from the synergistic effect of Pd and MXene. The existence of MXene increases metallic Pd on the surface. This study on MXenes as supports of Pd nanoparticles for two-electron oxygen reduction provides extensive reference significance to H 2 O 2 generation. [ABSTRACT FROM AUTHOR]