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/Ti3C2Tx-Y (Y: 16, 32, and 320, Y indicates the quality of Co(NO3)2) catalyst was synthesized by loading PtCo alloy on Ti3C2Tx. The PtCo/Ti3C2Tx-32 exhibited the best HER performance with low overpotentials (36 and 101 mV) to reach a current density of 10 mA cm−2, 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 and stability of PtCo/Ti3C2Tx-32 can be attributed as follows: Ti3C2Tx has a unique two-dimensional structure, which can provide a large number of attachment sites for the PtCo alloy, thus exposing more active sites; on the other hand, it can 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/Ti3C2Tx catalyst more hydrophilic, which can accelerate 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 PtCo/Ti3C2Tx catalyst has a suitable ΔGH* value. This study can be expected to provide some references for the design and synthesis of Ti3C2Tx supported alloy electrocatalysts with high activity and stability for HER.

Increasing the loading density of nanoparticles on carbon support is essential for making Pt-alloy/C catalysts practical in H2-air fuel cells. The challenge lies in increasing the load-ing while suppressing the sintering of Pt-alloy nanoparticles. This work presents a 40% Pt-weighted sub-3 nm PtCo/C alloy catalysts via a simple incipient wetness impregnation method. By carefully optimizing the synthetic conditions such as Pt/Co ratios, calcination temperature and time, the size of supported PtCo alloy nanoparticles is successfully con-trolled below 3 nm, and a high electrochemical surface area achieves of 94 m2/g is achieved, which is 2.8 times of commercial PtCo/C-TKK catalysts. Demonstrated by elec-trochemical oxygen reduction reaction, PtCo/C alloy catalysts present an enhanced mass activity of 0.45 A/mg at 0.9 V vs. RHE, which is 1.7 times that of PtCo/C-TKK catalyst. Therefore, the developed PtCo/C alloy catalyst can potentially be a highly practical cata-lyst for H2-air fuel cells.