Macroporous high‐entropy spinel oxide monoliths as efficient oxygen evolution electrocatalyst

In this paper, macroporous high‐entropy spinel oxide (HESO) (Fe 0.2 Ni 0.2 Co 0.2 Mn 0.2 Zn 0.2 ) 3 O 4 monoliths were successfully fabricated via a sol–gel method followed by calcination. Appropriate polyacrylic acid and propylene oxide contents allow the formation of three‐dimensional co‐continuous xerogel monoliths, and the water/glycerol ratio controls the macropore size of monoliths. Subsequent calcination achieves the precipitation of HESO (Fe 0.2 Ni 0.2 Co 0.2 Mn 0.2 Zn 0.2 ) 3 O 4 with a singular phase and exceptional structural stability. The macroporous HESO (Fe 0.2 Ni 0.2 Co 0.2 Mn 0.2 Zn 0.2 ) 3 O 4 demonstrates remarkable performance in the oxygen evolution reaction (OER) with an overpotential of 333 mV at 100 mA cm −2 and a Tafel slope of 43.2 mV dec –1 , surpassing that of RuO 2 (391 mV) under identical conditions. Furthermore, the catalytic stability of the HESO catalyst remains superior even after 24 h of testing. This process offers a promising avenue for the development of macroporous high‐entropy oxide OER catalysts for overall water splitting.