Cyclic Trinickel(II) Clusters in a Metal‐Azolate Framework for Efficient Overall Water Splitting

Abstract Herein, a stable metal‐azolate framework with cyclic trinickel(II) clusters, namely [Ni 3 ( μ 3 ‐O)(BTPP)(OH)(H 2 O) 2 ] ( Ni‐BTPP , H 3 BTPP=1,3,5‐tris((1 H ‐pyrazol‐4‐yl)phenylene)benzene), achieved a current density of 50 mA cm −2 at a cell voltage of 1.8 V in 1.0 M KOH solution, while the current density of 20%Pt/C@NF||IrO 2 @NF is just 35.8 mA cm −2 at 2.0 V under the same condition. Moreover, no obvious degradation was observed over 12 hours of continuous operation at a large current density of 50 mA cm −2 . Theoretical calculations revealed that the μ 3 ‐O atom in the cyclic trinickel(II) cluster serves as hydrogen‐bonding acceptor to facilitate the dissociation of a H 2 O molecule adsorbed on the adjacent Ni(II) ion, giving a lower energy barrier of H 2 O dissociation compared with Pt/C; meanwhile, the μ 3 ‐O atom can also participate in the water oxidation reaction to couple with the adjacent *OH adsorbed on Ni(II) ion, providing a low‐energy coupling pathway, thus Ni‐BTPP achieves a high performance for overall water splitting.