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Adv. Mater. 2019, 31, 1901174
2019-07-11 14:39  

Adv. Mater. 2019, 31, 1901174

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Haijing Yan, Ying Xie, Aiping Wu, Zhicheng Cai, Lei Wang, Chungui Tian,*

Xiaomeng Zhang, and Honggang Fu*, Anion-Modulated HER and OER Activities of 3D Ni–V-Based Interstitial Compound Heterojunctions for High-Efficiency and Stable Overall Water Splitting. (Adv. Mater. 2019, 1901174)

The popular bifunctional catalysts usually show good activity for one of the half reactions but at the expense of the activity for the other half reaction, resulting in a moderate water splitting ability.Although there are some reports on coupling good HER and OER catalysts in the same medium, the catalysts in two electrodes usually show large differences in their metal elements, which can make the preparation inconvenient and cause potential mutual interference due to possible dissolution and redeposition of the catalysts during the reaction. Therefore, the coupling of good HER and OER catalysts with an easy preparation technique and minimal mutual influence is desirable for efficient overall water splitting.

Herein, anion-modulation of 3D Ni–V-based transition metal interstitial compound (TMIC) heterojunctions supported on nickel foam (Ni3N-VN/NF and Ni2P-VP2/NF) as coupled hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalysts for efficient overall water splitting is demonstrated. The heterointerface in

 

Ni3N-VN has a suitable H* absorption energy, being favorable for enhancing HER activity with onset overpotential (ηonset) of zero and Tafel slope of 37 mV dec−1 in 1 m KOH (close to that of Pt/C/NF). For the OER, the synergy of Ni2P-VP2 with oxide species can give enhanced activity with ηonset of 220 mV and Tafel slope of 49 mV dec1. 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 Ni3N-VN/NF and Ni2P-VP2/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 cm2, and remarkable durability for 100 h. It can be driven by a solar cell (1.5 V), indicating its potential to store intermittent energy.The nitridebased heterojunction (Ni3N-VN/NF) exhibits excellent activity for the HER in alkaline media (close to that of Pt/C/NF), while Ni2P-VP2/NF shows an OER performance superior to that of RuO2/NF. This work opens up a promising avenue to create superior and easily coupled HER and OER catalysts for overall water splitting.

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