Single Crystals of α-MoO 3 -Intercalated {Ni(H 2 O) 6 } 2+ and Electrocatalytic Water Reduction: Toward a Class of Molybdenum Bronzes.

We have successfully intercalated {Ni II (H 2 O) 6 } 2+ into the α-MoO 3 layer, leading to the isolation of green single crystals of [Mo VI 2 O 6 (CH 3 COO){Ni II (H 2 O) 6 } 0.5 ]·H 2 O ( 1 ). The homogeneous electrochemistry of 1 in its aqueous solution exhibits electrocatalytic hydrogen evolution reaction (HER) with concomitant electrochemical deposition of [HMo 3 VI Mo V O 12 (CH 3 COO){Ni II (H 2 O) 5 (OH)}] ( 2 ). Compound 2 , a new molybdenum bronze, acts as an efficient and stable heterogeneous electrocatalyst for water reduction to molecular hydrogen. This work represents the first paradigm of a molybdenum bronze intercalating a transition metal-aqua ion.