Heterometallic Polyoxotitanium Clusters as Bifunctional Electrocatalysts for Overall Water Splitting.

Incorporating heterometal into titanium-oxygen clusters (TOCs) is an effective way to improve its catalytic activity. Herein, we synthesize three novel heterometallic TOCs with the formula of [Ti 6 Cu 2 O 7 (Dmg) 2 (OAc) 4 ( i PrO) 6 ][H 2 Ti 6 Cu 2 O 7 (Dmg) 2 (OAc) 4 ( i PrO) 8 ] ( {Ti 6 Cu 2 } ), [Ti 8 Cu 2 O 9 (Dmg) 2 (OAc) 2 ( i PrO) 12 ] ( {Ti 8 Cu 2 } ), and [Ti 10 Co 2 O 6 (Dmg) 2 (Pdc) 4 ( i PrO) 18 Cl 3 ] ( {Ti 10 Co 2 } , DmgH 2 = dimethylglyoxime; PdcH 2 = pyridine-2,3-dicarboxylic acid) using dimethylglyoxime and different carboxylates as the synergistic ligands. By depositing the clusters {Ti 6 Cu 2 } and {Ti 10 Co 2 } on carbon cloth as electrodes, we investigated the electrocatalytic performance of TOCs for full water splitting for the first time. To reach a 10 mA cm -2 current density in an alkaline solution, the {Ti 10 Co 2 } @CC electrode needs an overpotential as low as 120 and 400 mV for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), respectively. In addition, full water-splitting equipment with {Ti 10 Co 2 } @CC as a cathode and an anode need only 1.67 V to deliver a current density of 10 mA cm -2 . Our work confirmed the potential of noble metal-free TOCs as bifunctional cluster-based electrocatalysts for water splitting, and their activities can be tuned by doping with different metal ions.