Boosted water splitting with high entropy metal oxide–CeO ₂ heterostructure and redox additive

Efficient bifunctional electrocatalysts are essential for advancing alkaline water splitting, addressing oxygen evolution (OER) and hydrogen evolution reactions (HER). This work employs redox-additive electrolytes to enhance electrode-electrolyte interactions through interface engineering. A high-entropy metal oxide (HEMO)-CeO2 heterostructure (Zn, Ni, Co, Fe, Ag) achieved an OER overpotential of 380 mV at 10 mA cm−2, reduced to 209 mV with 0.1 M KI addition, alongside stable operation for 20 hours. For HER, integrating KI in electrolyte led to incredible improvement in performance with lowering of overpotential from 223 mV to 148 mV, revealing improved catalytic activity. In a bifunctional cell, 1.7 V was required at 10 mA cm−2, further reduced to 1.5 V after prolonged operation. This study demonstrates the potential of KI-integrated electrolytes to significantly improve HEMO-CeO2 performance for sustainable hydrogen production.