Europium Oxide Evoked Multisite Synergism to Facilitate Water Dissociation for Alkaline Hydrogen Evolution

Abstract Exploring an efficient nonnoble metal catalyst for hydrogen evolution reaction (HER) is critical for industrial alkaline water electrolysis. However, it remains a great challenge due to the additional energy required for H─OH bond cleavage and the lack of enough H 2 O adsorption sites for most catalysts. Herein, the integration of oxophilic Eu 2 O 3 with NiCo alloy with evoked multisite synergism to facilitate water dissociation for alkaline HER is proposed. The optimized Eu 2 O 3 ‐NiCo exhibits excellent HER activity with a low overpotential of only 60 mV at 10 mA cm −2 and good electrochemical stability, which is superior to that of Eu 2 O 3 ‐free NiCo and comparable to benchmark Pt/C. The key roles of Eu 2 O 3 on the enhanced HER performance of Eu 2 O 3 ‐NiCo are identified by in situ Raman spectroscopy and theoretical calculations. It is discovered that the Eu 2 O 3 with strong oxophilicity facilitates the adsorption of H 2 O and the breakage of H─OH bonding while evoking the electron redistribution at Eu 2 O 3 /NiCo interface and accelerating the Volmer step in alkaline HER. Furthermore, the obtained Eu 2 O 3 ‐NiCo as both anode and cathode displays excellent overall water‐splitting activity and stability in 1.0 M KOH solution. It is believed that this study provides an important inspiration to design high‐performance electrocatalysts toward HER based on rare‐earth materials.