Facile synthesis of nitrogen, phosphorus and sulfur tri-doped carbon nanosheets as efficient oxygen electrocatalyst for rechargeable Zn-air batteries

Abstract

The rechargeable Zn-air battery plays vital roles in renewable energy storage and conversion, but the scarcity of highly efficient air cathode electrocatalysts severely hampers its commercial popularizing. Heteroatoms-doped carbon materials have attracted many interests, because the resulted dopants synergistic effect always brings about extraordinary electrocatalytic activities. Herein, a simple pyrolysis strategy of thiourea, phytic acid and graphene oxide was developed to prepare N, P and S tri-doped carbon nanosheets, featuring sheet structure with specific surface area of 479 m2 g−1 and sufficient dopants (3.78 at% N, 7.97 at% P, and 1.36 at% S). Benefiting from the dominated graphitic and pyridinic N moieties, as well as abundant P-C and S-C functional groups, all of which are desired active species for oxygen electrochemistry, the synthesized tri-doped carbon nanosheets exhibit superior oxygen reduction performance and enhanced oxygen evolution activity in alkaline electrolyte. As the air cathode electrocatalysts for rechargeable Zn-air batteries, the decreased charge–discharge potential gaps and robust cycling stability are observed, even superior to those of noble-metal Pt/C benchmarks. The interconnected porous architecture with high surface area, multiple active species, and significant electric conductivity capability are considered as main factors for the enhanced electrochemical activities of this tri-doped carbon material.