Anion-Modulated HER and OER Activities of 3D Ni-V-Based Interstitial Compound Heterojunctions for High-Efficiency and Stable Overall Water Splitting.
basic_science · Level V
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- Also identified by DOI 10.1002/adma.201901174.
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Abstract
Overall water splitting driven by a low voltage is crucial for practical H<sub>2</sub> evolution, but it is challenging. Herein, anion-modulation of 3D Ni-V-based transition metal interstitial compound (TMIC) heterojunctions supported on nickel foam (Ni<sub>3</sub> N-VN/NF and Ni<sub>2</sub> P-VP<sub>2</sub> /NF) as coupled hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalysts for efficient overall water splitting is demonstrated. The heterointerface in Ni<sub>3</sub> N-VN has a suitable H* absorption energy, being favorable for enhancing HER activity with onset overpotential (η<sub>onset</sub> ) of zero and Tafel slope of 37 mV dec<sup>-1</sup> in 1 m KOH (close to that of Pt/C/NF). For the OER, the synergy of Ni<sub>2</sub> P-VP<sub>2</sub> with oxide species can give enhanced activity with η<sub>onset</sub> of 220 mV and Tafel slope of 49 mV dec<sup>-1</sup> . The good activity is ascribed to heterointerface for activating the intermediates, good conductivity of TMICs for electron-transfer, and porous structure facilitation of mass-transport. Additionally, the minimal mutual influence of Ni<sub>3</sub> N-VN/NF and Ni<sub>2</sub> P-VP<sub>2</sub> /NF allows easy coupling for efficient overall water splitting with a low driving voltage (≥1.43 V), a voltage of 1.51 V at 10 mA cm<sup>-2</sup> , and remarkable durability for 100 h. It can be driven by a solar cell (1.5 V), indicating its potential to store intermittent energy.