Etched and doped Co9S8/graphene hybrid for oxygen electrocatalysis

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Abstract

Simultaneous etching and doping of cobalt sulfides–graphene hybrid with NH ₃-plasma effectively enhances the oxygen electrocatalytic activity.

Abstract

Highly efficient electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have been regarded as the core elements in a wide range of renewable energy technologies. Surface engineering of the electrocatalysts is one of the most popular strategies to improve their catalytic activity. Herein, we, for the first time, designed an advanced bi-functional electrocatalyst for the ORR and OER by simultaneously etching and doping a cobalt sulfides–graphene hybrid with NH ₃-plasma. The graphene supported Co ₉S ₈ nanoparticles were prepared (denoted as Co ₉S ₈/G) first, followed by the NH ₃-plasma treatment, which could not only lead to nitrogen doping into both Co ₉S ₈ and graphene, but also partially etch the surface of both Co ₉S ₈ and graphene. The heteroatom doping could efficiently tune the electronic properties of Co ₉S ₈ and graphene, and the surface etching could expose more active sites for electrocatalysis, which can contribute significantly to the enhanced electrocatalytic performance for ORR and OER. The electrochemical results revealed that the etched and N-doped Co ₉S ₈/G shows excellent ORR activity, which is close to that of the commercial Pt/C catalyst, and great OER activity. The strategy developed here provides a novel and efficient approach to prepare hybrid bi-functional electrocatalysts for ORR and OER.

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Co3O4 Nanocrystals on Graphene as a Synergistic Catalyst for Oxygen Reduction Reaction

Jigang Zhou, Yongye Liang, Tom Regier … (2011)

Catalysts for oxygen reduction and evolution reactions are at the heart of key renewable energy technologies including fuel cells and water splitting. Despite tremendous efforts, developing oxygen electrode catalysts with high activity at low costs remains a grand challenge. Here, we report a hybrid material of Co3O4 nanocrystals grown on reduced graphene oxide (GO) as a high-performance bi-functional catalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). While Co3O4 or graphene oxide alone has little catalytic activity, their hybrid exhibits an unexpected, surprisingly high ORR activity that is further enhanced by nitrogen-doping of graphene. The Co3O4/N-doped graphene hybrid exhibits similar catalytic activity but superior stability to Pt in alkaline solutions. The same hybrid is also highly active for OER, making it a high performance non-precious metal based bi-catalyst for both ORR and OER. The unusual catalytic activity arises from synergetic chemical coupling effects between Co3O4 and graphene.

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Toward the rational design of non-precious transition metal oxides for oxygen electrocatalysis

Wesley T. Hong, Marcel Risch, Kelsey A. Stoerzinger … (2015)

The rational design of non-precious transition metal perovskite oxide catalysts holds exceptional promise for understanding and mastering the kinetics of oxygen electrocatalysis instrumental to artificial photosynthesis, solar fuels, fuel cells, electrolyzers, and metal–air batteries. In this Review, we discuss the state-of-the-art understanding of non-precious transition metal oxides that catalyze the oxygen reduction and evolution reactions. Understanding and mastering the kinetics of oxygen electrocatalysis is instrumental to making use of photosynthesis, advancing solar fuels, fuel cells, electrolyzers, and metal–air batteries. We first present key insights, assumptions and limitations of well-known activity descriptors and reaction mechanisms in the past four decades. The turnover frequency of crystalline oxides as promising catalysts is also put into perspective with amorphous oxides and photosystem II. Particular attention is paid to electronic structure parameters that can potentially govern the adsorbate binding strength and thus provide simple rationales and design principles to predict new catalyst chemistries with enhanced activity. We share new perspective synthesizing mechanism and electronic descriptors developed from both molecular orbital and solid state band structure principles. We conclude with an outlook on the opportunities in future research within this rapidly developing field.