Controlling Electronic Metal‐Support Interaction for Proficient Electrocatalytic Water Splitting

The efficiency of electrochemical water splitting is primarily limited by the anodic oxygen evolution reaction (OER), which is hindered by high energy barriers, sluggish kinetics, and considerable overpotentials, much more so than the cathodic hydrogen evolution reaction (HER). The Ni‐based catalysts have gained considerable interest due to the redox‐active Ni 2+ /Ni 3+ couple. Enhancing the oxidation from Ni 2+ to Ni 3+ is a key strategy to improve OER performance. In this study, we show through comprehensive structural and surface analyses that the highly reducible CeO 2 –ZrO 2 support in the Ce 0.6 Zr 0.35 Ni0 .05 O 2‐δ combustion synthesized solid solution significantly promotes the Ni 2+ → Ni 3+ oxidation and facilitates lattice oxygen evolution during OER. In contrast, the non‐reducible and inert Al 2 O 3 support in the composite NiO/Al 2 O 3 does not aid Ni oxidation during OER, but effectively supports Ni 2+ reduction during HER, making NiO/Al 2 O 3 a superior cathodic catalyst. Our in‐depth study demonstrates that the combination of Ce 0.6 Zr 0.35 Ni0 .05 O 2‐δ as the anode and NiO/Al 2 O 3 as the cathode in a two‐electrode alkaline water‐splitting device offers a cost‐effective and efficient catalyst pair with excellent overall performance for practical alkaline electrolysis.