MXene Anchored with Platinum Cobalt Alloy as an Efficient and Stable Electrocatalyst for Hydrogen Evolution

It is a great challenge to prepare efficient and stable electrocatalysts for hydrogen evolution (HER) using non-precious metals. In this study, a series of PtCo/Ti₃C₂T_x-Y (Y: 16, 32, and 320, Y indicates the quality of Co(NO₃)₂) catalysts were synthesized by loading PtCo alloy on Ti₃C₂T_x. The PtCo/Ti₃C₂T_x-32 catalyst showed the best HER performance, reaching a current density of 10 mA cm^-2 with low overpotential (36 and 101 mV) and small Tafel slopes (66.37 and 105.17 mV dec^-1) in 0.5 mol L^-1 H₂SO₄ and 1 mol L^-1 KOH solution. The excellent HER activity of PtCo/Ti₃C₂T_x-32 can be attributed as follows: Ti₃C₂T_x has a unique two-dimensional structure, which can provide a large number of attachment sites for the PtCo alloy, hence exposing more active sites; on the other hand, it can also provide a fast and efficient conductive network for electron transport during electrocatalytic processes, thus enhancing the connectivity between electrolyte and catalyst. PtCo alloy makes the PtCo/Ti₃C₂T_x catalyst more hydrophilic, accelerating the release rate of bubbles. The DFT calculation results showed that the energy barrier of HER is reduced because the charge around Pt is redistributed by Co after alloying Pt and Co, so that the PtCo/Ti₃C₂T_x catalyst has a suitable ΔG_H* value. This study can be expected to provide some references for the design and synthesis of Ti₃C₂T_x-supported alloy electrocatalysts with high activity and stability for HER.