Topotactically Transformed Polygonal Mesopores on Ternary Layered Double Hydroxides Exposing Under-Coordinated Metal Centers for Accelerated Water Dissociation

Hao Sun; Ling Chen; Yuebin Lian; Wenjuan Yang; Ling Lin; Yufeng Chen; Jiabin Xu; Dan Wang; Xiaoqin Yang; Mark H Rümmerli; Jun Guo; Jun Zhong; Zhao Deng; Yan Jiao; Yang Peng; Shizhang Qiao

doi:10.1002/adma.202006784

Topotactically Transformed Polygonal Mesopores on Ternary Layered Double Hydroxides Exposing Under-Coordinated Metal Centers for Accelerated Water Dissociation

Adv Mater. 2020 Dec;32(52):e2006784. doi: 10.1002/adma.202006784. Epub 2020 Nov 13.

Authors

Hao Sun^{1

2}, Ling Chen³, Yuebin Lian^{1

2}, Wenjuan Yang⁴, Ling Lin^{1

2}, Yufeng Chen⁵, Jiabin Xu⁵, Dan Wang^{1

2}, Xiaoqin Yang^{1

2}, Mark H Rümmerli^{1

2}, Jun Guo⁶, Jun Zhong⁵, Zhao Deng^{1

2}, Yan Jiao³, Yang Peng^{1

2}, Shizhang Qiao³

Affiliations

¹ Soochow Institute for Energy and Material Innovations, College of Energy, Soochow University, Suzhou, 215006, China.
² Key Laboratory of Advanced Carbon Materials and Wearable Energy Technologies of Jiangsu Province, Suzhou, 215006, China.
³ School of Chemical Engineering and Advanced Materials, The University of Adelaide, Adelaide, SA 5005, Australia.
⁴ SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen, 518060, China.
⁵ Institute of Functional Nano and Soft Materials Laboratory (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou, 215123, P. R. China.
⁶ Analysis and Testing Center, Soochow University, Suzhou, 215123, China.

PMID: 33184955
DOI: 10.1002/adma.202006784

Abstract

Layered double hydroxides (LDHs) have been recognized as potent electrocatalysts for oxygen evolution reaction (OER), but are lacking in hydrogen evolution reaction (HER) activities due to the sluggish kinetics of water dissociation in alkaline medium. Herein, aiming to simultaneously bolster the HER and OER kinetics, a metal-organic framework (MOF) mediated topotactic transformation tactic is deployed to fabricate holey ternary CoFeNi LDHs on nickel foam, exposing polygonal mesopores with atomistic edge steps and lattice defects. The optimized catalyst requires only an external voltage of 1.49 V to afford the water splitting current density of 10 mA cm^-2 apart from the superb electrolytic stability, far surpassing the benchmark Pt/C||RuO₂ couple. More importantly, mechanistic investigations utilizing advanced spectroscopies in conjunction with density function theory (DFT) understandings unravel while the synergetic effect among under-coordinated metal centers lowers the energy barrier of water dissociation, Fe-doping enables further modulating the d-band density of states (DOS) of Co and Ni in favor of intermediates binding, thereby promoting the intrinsic HER activity. Operando Raman studies reveal negligible structural change of the LDHs during the HER process, whereas for OER the active sites can quickly turn into oxyhydroxides in the presence of lattice defects and under-coordinated metal centers.

Keywords: defect engineering; layered double hydroxides; metal-organic frameworks; overall water splitting.

Abstract

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