From nine to five: A compositional subtraction strategy to identify Ti as the key dopant in FeCoNiAl-based high-entropy catalysts for enhanced OER activity and stability

Conventional trial-and-error optimization of high-entropy compounds (HECs) for the oxygen evolution reaction (OER) is inefficient. Herein, we propose a “compositional subtraction” strategy to screen active components in a nine-metal HEC system (Fe, Co, Ni, Al, Ti, Cr, Mn, Cu, and Zr). Stepwise elimination identifies Ti as the decisive dopant, and a series of S-FeCoNiAl-Ti x (x = 0–2.0) samples is synthesized. The S-FeCoNiAl-Ti 1.0 catalyst exhibits low overpotentials (241 mV at 10 mA cm −2 and 295 mV at 100 mA cm −2 ) and retains 95.3% of its initial activity after 72 h. XPS analysis indicates that Ti doping shifts the Fe/Co/Ni binding energies to lower values, while DFT calculations reveal that Ti elevates the d-band centers and weakens intermediate adsorption. Volcano plots identify Co as the primary active site, and Ti doping reduces the theoretical OER overpotential from 280 to 247 mV. This combinatorial screening strategy combined with d-band modulation provides a new perspective for the development of high-performance HEC-based OER electrocatalysts.