Phosphorus Regulates Coordination Number and Electronegativity of Cobalt Atomic Sites Triggering Efficient Photocatalytic Water Splitting.

Zhao, Yuqi; Wu, Xi; Wang, Hengliang; Ma, Ming; Tian, Jian; Wang, Xin · Nano Lett · 2024

basic_science · Level V

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Abstract

Optimizing the local electronic structure of a single-atom catalyst (SAC) is crucial for efficient photocatalytic hydrogen evolution reactions. This study synthesized a Co-P<sub>4</sub>/g-C<sub>3</sub>N<sub>4</sub> heterostructure by selective phosphidation of the Co metal-organic framework/graphitic carbon nitride (Co-MOF/g-C<sub>3</sub>N<sub>4</sub>), converting the Co-O<sub>6</sub> configuration into a highly electronegative, coordinatively unsaturated Co-P<sub>4</sub> configuration anchored to a carbon matrix. P-doping induces strong charge redistribution, shifting the <i>d</i>-band center toward the Fermi level, transforming the Co sites from an electron-deficient state to an electron-rich state, and resulting in a significant reduction in the free energy barrier for HER to -0.08 eV. The Co-P<sub>4</sub>/<i>g</i>-C<sub>3</sub>N<sub>4</sub> heterostructure demonstrated a HER rate of 13.51 mmol g<sup>-1</sup> h<sup>-1</sup>, approximately 4.82-8.35 times greater than those of photocatalysts loaded with noble metals. The apparent quantum efficiency (AQE) was 28.45% at 380 nm. The synergistic effect of the low coordination number and high electronegativity metal sites significantly enhances the photocatalytic HER performance.