Journal
ADVANCED MATERIALS
Volume 33, Issue 9, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adma.202007377
Keywords
electrochemical water splitting; local electric enhancement; mass transport; oxygen evolution reaction; tip-enhanced aggregation
Categories
Funding
- Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program [2017BT01N111]
- Shenzhen Geim Graphene Center
- National Nature Science Foundation of China [51578310, 52061160482]
- Guangdong Province Science and Technology Department [2020A0505100014]
- Tsinghua Shenzhen International Graduate School Overseas Collaboration Project
- Agency for Science, Technology, and Research (A*STAR) by AME Individual Research Grant [A1983c0026]
- ITC via Hong Kong Branch of National Precious Metals Material Engineering Research Center (NPMM)
- City University of Hong Kong [9380100, 9610478, 1886921]
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In this study, NiFe alloy nanocone arrays were used to enhance the oxygen evolution reaction (OER) rate and outperform state-of-the-art OER electrocatalysts. The high-curvature tips on the nanocones induce a local electric field that significantly increases the concentration of hydroxide ions near the active sites, promoting OER activity. This local field enhanced OER kinetics is suggested to be a generic effect applicable to other OER catalysts.
The slow kinetics of oxygen evolution reaction (OER) causes high power consumption for electrochemical water splitting. Various strategies have been attempted to accelerate the OER rate, but there are few studies on regulating the transport of reactants especially under large current densities when the mass transfer factor dominates the evolution reactions. Herein, NixFe1-x alloy nanocones arrays (with approximate to 2 nm surface NiO/NiFe(OH)(2) layer) are adopted to boost the transport of reactants. Finite element analysis suggests that the high-curvature tips can enhance the local electric field, which induces an order of magnitude higher concentration of hydroxide ions (OH-) at the active sites and promotes intrinsic OER activity by 67% at 1.5 V. Experimental results show that a fabricated NiFe nanocone array electrode, with optimized alloy composition, has a small overpotential of 190 mV at 10 mA cm(-2) and 255 mV at 500 mA cm(-2). When calibrated by electrochemical surface area, the nanocones electrode outperforms the state-of-the-art OER electrocatalysts. The positive effect of the tip-enhanced local electric field in promoting mass transfer is also confirmed by comparing samples with different tip curvature radii. It is suggested that this local field enhanced OER kinetics is a generic effect to other OER catalysts.
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