Title: Morphology Control of Carbon-Free Spinel NiCo ₂ O ₄ Catalysts for Enhanced Bifunctional Oxygen Reduction and Evolution in Alkaline Media

Abstract

Spinel NiCo₂O₄ is considered a promising precious metal-free catalyst that is also carbon-free for oxygen electrocatalysis. Current efforts mainly focus on optimal chemical doping and substituent to tune its electronic structures for enhanced activity. Here, we study its morphology control and elucidate the morphology-dependent catalyst performance for bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Three types of NiCo₂O₄ catalysts with significantly distinct morphologies were prepared using temple-free, Pluronic-123 (P-123) soft, and SiO₂ hard templates, respectively, via hydrothermal methods following by a calcination. While the hard-template yields sphere-like dense structures, soft-template assists the formation of a unique nano-needle cluster assembly containing abundant meso- and macro pores. Furthermore, the effect of morphology of NiCo₂O₄ on their corresponding bifunctional catalytic performance was systematically investigated. The flower-like nano-needle assembly NiCo₂O₄ catalyst via the soft template method exhibited the highest catalytic activity and stability for both ORR and OER. In particular, it exhibited an onset and half-wave potentials of 0.94 and 0.82 V vs. RHE, respectively, for the ORR in alkaline media. Although it is still inferior to Pt, the NiCo₂O₄ represents one of the best ORR catalyst compared to other reported carbon-free oxides. Meanwhile, remarkable OER activity and stability were achievedmore » with an onset potential of 1.48 V and a current density of 15 mA/cm² at 1.6 V, showing no activity loss after 20,000 potential cycles (0 to 1.9 V). The demonstrated stability is even superior to Ir for the OER. The morphology-controlled approach provides an effective solution to create a robust 3D architecture with increased surface areas and enhanced mass transfer. More importantly, the soft template can yield high degree of spinel crystallinity with ideal stoichiometric ratios between Ni and Co, thus promoting structural integrity with enhanced electrical conductivity and catalytic properties.« less

Authors:

Devaguptapu, Surya V. ^[1]; Hwang, Sooyeon ^[2]; Karakalos, Stavros  ^[3];

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Zhao, Shuai ^[4]; Gupta, Shiva ^[1]; Su, Dong  ^[2];

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Xu, Hui ^[4]; Wu, Gang  ^[1]

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• Search OSTI.GOV for ORCID "0000-0003-0885-6172"
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+ Show Author Affiliations

1. Univ. at Buffalo, NY (United States). Dept. of Chemical and Biological Engineering
2. Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)
3. Univ. of South Carolina, Columbia, SC (United States). Dept. of Chemical Engineering
4. Giner Inc., Newston, MA (United States)

Publication Date:

2017-12-06

Research Org.:

Brookhaven National Lab. (BNL), Upton, NY (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); Univ. at Buffalo (SUNY), Buffalo, NY (United States); National Science Foundation (NSF); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Fuel Cell Technologies Office

OSTI Identifier:

1425005

Report Number(s):

BNL-114859-2017-JAAM
Journal ID: ISSN 1944-8244

Grant/Contract Number:  

SC0012704; CBET-1604392; EE000696

Resource Type:

Journal Article: Accepted Manuscript

Journal Name:

ACS Applied Materials and Interfaces

Additional Journal Information:

Journal Volume: 9; Journal Issue: 51; Journal ID: ISSN 1944-8244

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

29 ENERGY PLANNING, POLICY AND ECONOMY