Yeast Cells-Derived Hollow Core/Shell Heteroatom-Doped Carbon Microparticles for Sustainable Electrocatalysis Xiaoxi Huang, † Xiaoxin Zou, ∥ Yuying Meng, ‡ Elis ̌ ka Mikmekova ́ , # Hui Chen, ∥ Damien Voiry, § Anandarup Goswami, †,‡ Manish Chhowalla, § and Tewodros Asefa* ,†,‡,⊥ † Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States ‡ Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States § Department of Materials Science and Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States ⊥ Institute for Advanced Materials, Devices and Nanotechnology (IAMDN), Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States ∥ State Key Laboratory of Inorganic Synthesis & Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, China # Institute of Scientific Instruments of the ASCR, Brno 612 64, Czech Republic * S Supporting Information ABSTRACT: The use of renewable resources to make various synthetic materials is increasing in order to meet some of our sustainability challenges. Yeast is one of the most common household ingredients, which is cheap and easy to reproduce. Herein we report that yeast cells can be thermally transformed into hollow, core−shell heteroatom-doped carbon microparticles that can effectively electrocatalyze the oxygen reduction and hydrazine oxidation reactions, reactions that are highly pertinent to fuel cells or renewable energy applications. We also show that yeast cell walls, which can easily be separated from the cells, can produce carbon materials with electrocatalytic activity for both reactions, albeit with lower activity compared with the ones obtained from intact yeast cells. The results reveal that the intracellular components of the yeast cells such as proteins, phospholipids, DNAs and RNAs are indirectly responsible for the latter’s higher electrocatalytic activity, by providing it with more heteroatom dopants. The synthetic method we report here can serve as a general route for the synthesis of (electro)catalysts using microorganisms as raw materials. KEYWORDS: yeast, heteroatom-doped carbon, oxygen reduction, ORR, hydrazine electrooxidation ■ INTRODUCTION Over the past three decades, carbon nanomaterials have captured scientists’ imagination because of their fascinating properties as well as numerous potential applications. The past few years are no exception; amidst the strings of their known unique properties, the recent reports on carbon nanomaterials’ interesting catalytic properties for a number of important reactions, 1,2 e.g., the hydrogen evolution reaction (HER), 3 the oxygen evolution reaction (OER) 4,5 and the oxygen reduction reaction (ORR), 6−11 have been equally captivating. Moreover, because the materials can be synthesized from a variety of carbon precursors, both synthetic as well as natural ones, the materials have also been fascinating from a synthetic point of view. Although many synthetic substances such as dicyandia- mide, 3 polyaniline, 11 phenol and triphenylphosphine, 7 poly- pyrrole, 12,13 etc. have been successfully employed as precursors for making carbon materials with good electrocatalytic activity, most of them are toxic and unfriendly to the environment. Hence, natural precursors, especially those that are relatively cheap, abundant, renewable and environmental friendly, are preferred, and can constitute sustainable synthetic routes for these catalysts. Such precursors can generally be divided into two groups: (1) inanimate sources such as cellulose, 14 silk cocoon, 15 corn protein, 16 hemoglobin, 17 and human urine 18 and (2) living organisms such as microalgae, 19 grass, 20 plant Typha orientalis, 21 peat moss, 22 etc. More importantly, as many of these precursors inherently contain nitrogen and other heteroatoms, they can directly lead to heteroatom-doped carbon materials by simple pyrolysis. This is quite important because the heteroatom species present on carbon nanoma- terials are the ones mainly responsible for the materials’ electrocatalytic activity toward reactions such as ORR 20,23,24 and hydrazine oxidation reaction (HOR). 12,14,25 Moreover, because through powerful techniques of genetic engineering Received: November 7, 2014 Accepted: December 30, 2014 Published: December 30, 2014 Research Article www.acsami.org © 2014 American Chemical Society 1978 DOI: 10.1021/am507787t ACS Appl. Mater. Interfaces 2015, 7, 1978−1986