Anchoring a Pt-based alloy on oxygen-vacancy-defected MXene nanosheets for efficient hydrogen evolution reaction and oxygen reduction reaction.

Rational design and controllable synthesis of Pt-based materials with intimate interfacial contact open up the possibility for boosting the performance of the ORR (oxygen reduction reaction) and HER (hydrogen evolution reaction). However, it is still challenging to prevent the oxidation of Pt during the formation of alloys and to clarify the interfacial synergistic effects on the catalytic performance between Pt alloys and the dispersed substrate. Herein, the wet chemical stripping and intercalation methods were employed to synthesize a two-dimensional (2D) MXene with abundant defect sites, which can anchor PtCo/PtNi nanoparticles and prevent the oxidation of Pt during the process of atomic rearrangement at high temperatures. The obtained PtCo/MXene and PtNi/MXene displayed different phase compositions and alloying degrees on adjusting the annealing temperature. Electrochemical test results showed that the optimized HER and ORR electrocatalytic activities occurred at 700 °C. Compared with PtNi/MXene-700, PtCo/MXene-700 exhibited an HER overpotential of 1.3 mV at a current density of 10 mA cm, and a Tafel slope of 27.11 mV dec in 0.1 M HClO solution. Furthermore, PtCo/MXene-700 exhibited an ORR half-wave potential of 0.897 V, and a mass activity of 241.1 mA mg in 0.1 M HClO solution. This can be attributed to the formation of intermetallic compounds in PtCo/MXene. The electronic structure analysis showed that the enhanced performance could be assigned to the electron-capturing capability of the MXene, less oxidation of Pt and synergistic interactions between the Pt alloy and the MXene substrate. These findings provide a new strategy for the synthesis of highly active HER/ORR catalysts and broaden the way for the design of MXene-based catalysts.