Constructing Atomic Heterometallic Sites in Ultrathin Nickel-Incorporated Cobalt Phosphide Nanosheets via a Boron-Assisted Strategy for Highly Efficient Water Splitting.

Zhao, Yufei; Zhang, Jinqiang; Xie, Yuhan; Sun, Bing; Jiang, Junjie; Jiang, Wen-Jie; Xi, Shibo; Yang, Hui Ying et al. · Nano Lett · 2021

basic_science · Level V

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Abstract

Identification of active sites for highly efficient catalysts at the atomic scale for water splitting is still a great challenge. Herein, we fabricate ultrathin nickel-incorporated cobalt phosphide porous nanosheets (Ni-CoP) featuring an atomic heterometallic site (NiCo<sub>16-<i>x</i></sub>P<sub>6</sub>) via a boron-assisted method. The presence of boron induces a release-and-oxidation mechanism, resulting in the gradual exfoliation of hydroxide nanosheets. After a subsequent phosphorization process, the resultant Ni-CoP nanosheets are implanted with unsaturated atomic heterometallic NiCo<sub>16-<i>x</i></sub>P<sub>6</sub> sites (with Co vacancies) for alkaline hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The optimized Ni-CoP exhibits a low overpotential of 88 and 290 mV at 10 mA cm<sup>-2</sup> for alkaline HER and OER, respectively. This can be attributed to reduced free energy barriers, owing to the direct influence of center Ni atoms to the adjacent Co/P atoms in NiCo<sub>16-<i>x</i></sub>P<sub>6</sub> sites. These provide fundamental insights on the correlation between atomic structures and catalytic activity.