Noble Metal Phosphides Supported on CoNi Metaphosphate for Efficient Overall Water Splitting.

Transition metal metaphosphates and noble metal phosphides prepared under similar conditions are potential hybrid catalysts for electrocatalytic water splitting, which is of great significance for H 2 production. Herein, the structure and electrocatalytic activity of different noble metal species (i.e., Rh, Pd, Ir) on CoNiP 4 O 12 nanoarrays have been systematically studied. Due to the different formation energies of noble metal phosphides, the phosphides of Rh (RhP x ) and Pd (PdP x ) as well as the noble metal Ir are obtained under the same phosphorylation conditions perspectively. RhP x /CoNiP 4 O 12 and PdP x /CoNiP 4 O 12 exhibit much better HER activity than Ir/CoNiP 4 O 12 due to the advantages of phosphides. Density functional theory (DFT) calculations reveal that the extraordinary activity of RhP x /CoNiP 4 O 12 originated from the strong affinity to H 2 O and optimal adsorption for H*. The best RhP x /CoNiP 4 O 12 only requires a low overpotential of 30 and 234 mV to deliver 10 mA cm -2 for HER and OER, respectively, and therefore is effective for overall water splitting (requiring 1.57 V to achieve a current density of 10 mA cm -2 ). This work not only develops a novel RhP x /CoNiP 4 O 12 electrocatalyst for overall water splitting but also provides deep insight into the formation mechanism of noble metal phosphides.