Abstract
Developing superior efficient and durable oxygen reduction reaction (ORR) catalysts is critical for high-performance fuel cells and metal–air batteries. Herein, we successfully prepared a 3D, high-level nitrogen-doped, metal-free (N–pC) electrocatalyst employing urea as a single nitrogen source, NaCl as a fully sealed nanoreactor and gingko shells, a biomass waste, as carbon precursor. Due to the high content of active nitrogen groups, large surface area (1133.8 m2 g−1), and 3D hierarchical porous network structure, the as-prepared N–pC has better ORR electrocatalytic performance than the commercial Pt/C and most metal-free carbon materials in alkaline media. Additionally, when N–pC was used as a catalyst for an air electrode, the Zn–air battery (ZAB) had higher peak power density (223 mW cm−2), larger specific-capacity (755 mAh g−1) and better rate-capability than the commercial Pt/C-based one, displaying a good application prospect in metal-air batteries.
Highlights
The oxygen reduction reaction (ORR) plays a key role in fuel cells and metal–air batteries to implement electrochemical energy conversion [1,2]
N-doping has been considered to be one of the most effectual ways to enhance the electrocatalytic activities of carbon materials for ORR [18,19] because the N-doping can improve the electrical conductivity of carbon and change the charge distribution of the carbon atoms close to the dopants and make them positively charged, which is beneficial to the adsorption and reduction of oxygen at the corresponding sites and improving the ORR activity [7,20,21]
NaCl and urea were first mixed to a refined powder by ball-milling
Summary
The oxygen reduction reaction (ORR) plays a key role in fuel cells and metal–air batteries to implement electrochemical energy conversion [1,2]. Heteroatom-doped carbon materials, such as P-doped carbon xerogel [10], N-doped nanotube [11,12], S-doped carbon [13,14] and B-doped graphene [15], are among the most promising electrocatalysts for ORR due to their advantages of relatively low cost, abundant reserves, good electronic conductivity and environmental friendliness [16,17]. N-doping has been considered to be one of the most effectual ways to enhance the electrocatalytic activities of carbon materials for ORR [18,19] because the N-doping can improve the electrical conductivity of carbon and change the charge distribution of the carbon atoms close to the dopants and make them positively charged, which is beneficial to the adsorption and reduction of oxygen at the corresponding sites and improving the ORR activity [7,20,21]
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