S, N-Co-Doped Graphene-Nickel Cobalt Sulfide Aerogel: Improved Energy Storage and Electrocatalytic Performance.

Guanjie He,Wenyao Li,Rujia Zou,Jawwad A Darr,Tingting Zhao,Junqing Hu,Bo Li,Maria‐Magdalena Titirici,Mo Qiao,Yao Lu,Ivan P Parkin

doi:10.1002/advs.201600214

Abstract

Metal sulfides are commonly used in energy storage and electrocatalysts due to their redox centers and active sites. Most literature reports show that their performance decreases significantly caused by oxidation in alkaline electrolyte during electrochemical testing. Herein, S and N co‐doped graphene‐based nickel cobalt sulfide aerogels are synthesized for use as rechargeable alkaline battery electrodes and oxygen reduction reaction (ORR) catalysts. Notably, this system shows improved cyclability due to the stabilization effect of the S and N co‐doped graphene aerogel (SNGA). This reduces the rate of oxidation and the decay of electronic conductivity of the metal sulfides materials in alkaline electrolyte, i.e., the capacity decrease of CoNi2S4/SNGA is 4.2% for 10 000 cycles in a three‐electrode test; the current retention of 88.6% for Co—S/SNGA after 12 000 s current–time chronoamperometric response in the ORR test is higher than corresponding Co—S nanoparticles and Co—S/non‐doped graphene aerogels. Importantly, the results here confirm that the Ni—Co—S ternary materials behave as an electrode for rechargeable alkaline batteries rather than supercapacitors electrodes in three‐electrode test as commonly described and accepted in the literature. Furthermore, formulas to evaluate the performance of hybrid battery devices are specified.

Highlights

Graphene possesses unique properties, Metal sulfides are commonly used in energy storage and electrocatalysts due such as high theoretical surface area to their redox centers and active sites
Form graphite,[6] which leads to a and N co-doped graphene aerogel (SNGA). This reduces the rate of oxidation and the decay of electronic conductivity of the metal sulfides materials in alkaline electrolyte, i.e., the capacity decrease of CoNi2S4/SNGA is 4.2% for 10 000 cycles in a three-electrode test; the current retention of 88.6% for sharp decrease in surface area and kinetic ion transport, affecting the performance of these materials when used in energy storage[4] and electrocatalysis.[7]
The high-rate hybrid battery based on CoNi2S4/SNGA as the positive electrode and SNGA as the negative electrode delivered a high volumetric power density of 17.5 W cm−3 while it retained its high volumetric enegy density of 1.95 mWh cm−3 at the current of 1 mA

Summary

Introduction

Graphene possesses unique properties, Metal sulfides are commonly used in energy storage and electrocatalysts due such as high theoretical surface area to their redox centers and active sites. CoNi2S4/SNGA samples in our work for the three-electrode test proved to have superior specific capacity and cycling performances among the most of the reported for nickel/cobalt sulfide materials (see Table S2, Supporting Information, for comparison).

Results

Conclusion