Controllable moderate-temperature synthesis of high entropy PtIrCoNixFe1-x for superior hydrogen evolution reaction

Platinum (Pt) is renowned for its remarkable catalytic activity in the hydrogen evolution reaction (HER); however, its significant cost constrains its widespread use. Integrating Pt with transition metals optimizes its electronic structure, enhancing catalytic efficiency while reducing Pt reliance. This study reports the synthesis of PtIrCoNi_xFe_1-x high-entropy alloy nanoparticles (HEA NPs) via a moderate-temperature solvothermal method, offering a cost-efficient solution for achieving high HER activity with reduced Pt content. Structural analyses (PXRD, XPS, TEM, EDX mapping) confirm the formation of single-phase HEAs with evenly distributed elements. By adjusting Ni and Fe ratios, PtIrCoNi_2·9Fe_3.9 HEA NPs sample show superior HER activity, outperforming commercial Pt/C with a low overpotential of 27 mV at −10 mA cm⁻² and a Tafel slope of 37.8 mV dec⁻¹ in alkaline media. DFT simulations reveal that the enhanced HER activity of the HEAs is due to d-d electron interactions and multiple active sites that lower energy barriers. Ir-5d orbitals facilitate electron transfer, while Pt-5d orbitals act as an electron reservoir. Ni-3d, Fe-3d, and Co-3d orbitals near the Fermi level create an electron depletion center, further improving HER activity. These findings highlight the potential of PtIrCoNi_xFe_1-x HEA NPs as tunable HER electrocatalysts.