Nanocellulose/nitrogen and fluorine co-doped graphene composite hydrogels for high-performance supercapacitors

Three-dimensional graphene materials have been studied as typical supercapacitors electrode materials by virtue of their ultrahigh specific surface area and good ion transport capacity.However,improvement of the poor volumetric electrochemical performance of these graphene materials has been required although they have high gravimetric energy density.In this work,nanocellulose/nitrogen and fluorine co-doped graphene composite hydrogels(NC-NFGHs)were prepared through a convenient hydrothermal approach utilizing ammonium fluoride as the heteroatom source.Nanocellulose(NC)and high concentration of graphene oxide(GO)were utilized to adjust the structure of NC-NFGHs and increase their packing density.Subsequently,the aqueous symmetric supercapacitor based on NC-NFGH-80 exhibits remarkable gravimetric(286.6 F·g^(-1))and volumetric(421.3 F·cm^(-3))specific capacitance at 0.3 A·g^(-1),good rate performance,and remarkable cycle stability up to 10,000 cycles.Besides,the all-solid-state flexible symmetric supercapacitors(ASSC)fabricated by NC-NFGH-80 also delivered a large specific capacitance of 117.1 F·g^(-1)at 0.3 A·g^(-1)and long service life over 10,000 cycles at 10 A·g^(-1).This compact porous structure and heteroatom co-doped graphene material supply a favorable strategy for high-performance supercapacitors.

Fabrication of wide temperature lanthanum and cerium doped Cu/TNU-9 catalyst with excellent NH_(3)-SCR performance and outstanding SO_(2)+H_(2)O tolerance

The effects of La on the catalytic performance,SO_(2)and H2O resistance of Cu-Ce/TNU-9 catalyst were studied in the selective catalytic reduction of NO_(x)via ammonia(NH_(3)-SCR).The results show that the La doped Ce-Cu/TNU-9(CCL/T9)catalyst exhibits better SCR performance than Ce-Cu/TNU-9(CC/T9)and Cu/TNU-9(C/T9)in the wide temperature window(200-450℃)due to La benefiting from enhancing Cu^(+)+Ce^(4+)?Cu^(2+)-+Ce^(3+)to facilitate the electron transfer,which further accelerates the oxidation of NO into NO_(2)that leads to the"Fast SCR".The La can also enhance the surface acidic,redox property and is beneficial to the formation of oxygen vacancy.Meanwhile,the larger co ntent of Ce^(3+) can produce oxygen vacancy,resulting in rising SCR activity.The CCL/T9 has outstanding water and SO_(2) resistance,which may be due to the adso rbed S on the surface of these catalysts mainly existing in the form of a small amount of sulfate and sulfite,the decomposition of ammonium bisulphite under high temperature and the hydrophobicity of TNU-9 zeolite.