**3.4 Electrochemical analysis**

*Nanofibers - Synthesis, Properties and Applications*

substitution (DS), which can be obtained from Eq. (1):

nitrogen content determined by elementary analysis.

content of 0.9% and a degree of substitution of 0.11 [30].

**3.3 Thermal analysis**

CNFs (Tinitial = 327.87 °C).

*DS*

A more accurate way to measure reaction yield is by estimating the degree of

*glu N mal M N*

<sup>⋅</sup> <sup>=</sup> − ⋅

Where DS is the degree of substitution, Mglu the molar mass of the glucose monomer (162 g/mol), MN the molar mass of the nitrogen atom, Mmal the molar mass of the malononitrile group introduced into the cellulose (77 g), and %N the

By means of Eq. (1), Reaction 3 exhibits the highest DS value: 0.12. Despite not being very high, this value is close to those reported in the literature for reactions in which amino groups are introduced into the nanocellulose chain [29, 30]. For instance, the nitrogen content found in the functionalization reaction of cellulose nanocrystals with propargylamine was 0.79% [29]. Another study involving nanocellulose amination with 2-hydroxy-3-chloro-propylamine yielded a nitrogen

**Figure 4** shows the thermogravimetric analysis for pure and modified CNFs as well as the derivatives of the thermogravimetric curves (dTG). The thermal behavior of both materials exhibits a single decomposition event between 305 °C and 390 °C, with pure CNFs exhibiting greater loss of mass at the end of the process (**Figure 4**). The peak corresponding to maximum mass loss for the functionalized CNFs occurs at a temperature approximately 20 °C lower (Tmax = 349.05 °C) than that for pure CNFs (Tmax = 369.34 °C), as shown in **Figure 3**. Similarly, the beginning of the decomposition process for the modified CNFs also occurs at a temperature approximately 20 °C lower (Tinitial = 306.21 °C) than that for pure

*MM N*

<sup>100</sup> % (1)

%

**122**

**Figure 4.**

*TG and dTG curves for CNFs pure and modified.*

**Figure 5** shows cyclic voltammetry profiles for the CNFs electrocatalysts with and without mode modification at 5 mv/s scanning rate and applied potential ranging from −1.5 to 1.5 (vs Ag/AgCl). Conductivity of the electrocatalyst increases when cyan groups are introduced, as shown by the increase in area and current density.

This increase in conductivity has a positive effect concerning the use of the electrocatalyst as cathode in CO2 reduction.

CO2 conversion, whether thermal or electrochemical, is associated with high energy consumption due to CO2 being a very stable molecule. In the case of electrochemical reduction of CO2, the source of energy is electricity. It is possible to reduce CO2 completely by applying a higher potential. However, an appropriate catalyst can significantly reduce energy consumption and increase end-product selectivity.

**Figure 6** shows the polarization curves for pure and modified CNFs in an atmosphere of Ar and CO2. It is possible to observe that CNFs modification with cyan groups increases current density of the CO2 reduction reaction, which implies a higher CO2 conversion rate in the products. It also points to the onset potential for CO2 reduction shifting to more positive values as compared to those observed for pure CNFs. This may be attributed to adsorption/desorption of reaction intermediates in the polymer interface due to the presence of the cyan group.

The use of CNFs modified by the dicyan group has improved the catalytic efficiency of the electrocatalyst, thereby promoting CO2 reduction, probably due to higher availability of active sites in its fibrillar structure, especially cyan groups on the surface.

**Figure 5.**

*Cyclic voltammetry for CNFs pure and modified at a scanning rate of 5 mV s-1; electrolyte: K2SO4 0.5 Mol/L saturated with Ar at 25 °C. currents normalized by the geometric area of the electrode.*

#### **Figure 6.**

*Steady-state polarization curves for electrodes containing CNFs pure and modified at a scanning rate of 5 mV s−1, K2SO4 0.5 Mol/L saturated with Ar and CO2 at 25 °C. currents normalized by the geometric area of the electrode.*

### **4. Conclusion**

AFM results indicate no significant changes in the morphology of modified cellulose nanofibrils. The best experimental conditions for chemical functionalization is 1:3 molar ratio at room temperature. As reported in other studies on chemically modified cellulose, the degradation temperature for modified cellulose nanofibrils is lower than that for pure cellulose.

From the electrochemical perspective, introducing dicyanovinyl groups into the polymeric chain of cellulose nanofibrils has led to significantly higher electrocatalytic activity in CO2 reduction as compared to that for pure cellulose nanofibrils, shifting the onset potential to more positive values as compared to that observed for the reaction with Ar. Moreover, the CO2 molecule exhibits affinity for the cellulose polymer and the polymeric layer may play an inhibitory role in water reduction.

#### **Acknowledgements**

The authors thanks the Program of Post Graduation in Science of Materials - PPGCM of the Universidade Federal de São Carlos - UFSCar, campus Sorocaba for financial support.

**125**

**Author details**

Robson V. Pereira1

and Aparecido J. de Menezes3

São Carlos, São Paulo, Brasil

, Thais E. Gallina1

\*

Rio de Janeiro - UFRJ, Campus Macaé, Macaé - Rio de Janeiro, Brasil

Carlos - UFSCar, Campus Sorocaba, Sorocaba, São Paulo, Brasil

\*Address all correspondence to: jrmenezes@ufscar.br

provided the original work is properly cited.

2 Instituto de Física de São Carlos, IFSC, Universidade de São Paulo - USP,

, Marcelo A. Pereira-da-Silva2

1 Grupo de Eletroquímica e Polímeros Naturais (GEPN), Universidade Federal do

3 Grupo de Polímeros de Fontes Renováveis - GPFR, Universidade Federal de São

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

, Kênia S. Freitas1

*Electrochemical Behavior of Cellulose Nanofibrils Functionalized with Dicyanovinyl Groups*

*DOI: http://dx.doi.org/10.5772/intechopen.96181*

#### **Conflict of interest**

The authors declare no conflict of interest.

*Electrochemical Behavior of Cellulose Nanofibrils Functionalized with Dicyanovinyl Groups DOI: http://dx.doi.org/10.5772/intechopen.96181*
