Corrigendum to "A novel approach for electroanalytical determinations employing discharge of pseudocapacitor by electroactive species" [Analytica Chimica Acta 1006 (2018) 1-9].

The purpose of this Corrigendum is to cite and comment on an important reference that brings some support to the ideas developed in this paper and should be chronologically inserted into the history of advances in this area.

A novel approach for electroanalytical determinations employing discharge of pseudocapacitor by electroactive species.

In this paper, we introduce a novel approach for the detection of electroactive analytes by using oxidant species accumulated in pseudocapacitors surface. We demonstrated that pseudocapacitors can be quickly discharged when in contact with electroactive species. Thus, the variation of potential can be monitored during the discharging process and correlated with the analyte concentration. Based on this, two electroanalytical methods were proposed: continuous discharging detection and pulsed discharging detection. As a proof of concept, these methods were employed for glucose, fructose and sucrose detection using an ion chromatograph containing an electrochemical detector. Copper|cupric oxide in alkaline medium was used as the pseudocapacitive system. The obtained results proved to be very promising and the analytical curves showed good linearity in both methods. In addition, this novel approach for the detection of saccharides based on potential variation as a result of the discharging of the pseudocapacitor in contact with the analyte is very attractive because it does not require current reading. Therefore, our approach can be applied to other pseudocapacitive systems, opening new possibilities for several electroanalytical applications.

Insight into the Electro-Oxidation Mechanism of Glucose and Other Carbohydrates by CuO-Based Electrodes.

In this work, a new hypothesis for the electrocatalytic behavior of CuO electrodes is presented. Different from the established mechanism, here we discuss why CuIII species do not participate in the oxidation mechanism of carbohydrates. We show that hydroxyl ion adsorption and the semiconductive properties of the material play a more significant role in this process. The relationship between the flat band potential and the potential that begin oxidation suggests that the concentration of vacancies in the charge region acts upon the reactivity of the adsorbed hydroxyl ions through a partial charge transfer reaction. In the presence of carbohydrate molecules, the electron transfer is facilitated and involves the transfer of electrons from the adsorbed hydroxyl ions to the CuO film. This mechanism is fundamentally relevant since it helps the understanding of several experimental misleads. The results can also lead to obtaining better catalysts, since improvements in the material should focus on enhancing the semiconductive properties rather than the CuII/CuIII redox transition. The results shed light on different aspects of carbohydrate molecules oxidation that could lead to novel applications and possibly a better description of other semiconductor mechanisms in electrocatalysis.

Microwave-assisted synthesis of palladium nanoparticles intercalated nitrogen doped reduced graphene oxide and their electrocatalytic activity for direct-ethanol fuel cells.

Palladium nanoparticles decorated reduced graphene oxide (Pd-rGO) and palladium nanoparticles intercalated inside nitrogen doped reduced graphene oxide (Pd-NrGO) hybrids have been synthesized by applying a very simple, fast and economic route using microwave-assisted in-situ reduction and exfoliation method. The Pd-NrGO hybrids materials show good activity as catalyst for ethanol electro oxidation for direct ethanol fuel cells (DEFCs) as compared to Pd-rGO hybrids. The enhanced direct ethanol fuel cell can serve as alternative to fossil fuels because it is renewable and environmentally-friendly with a high energy conversion efficiency and low pollutant emission. As proof of concept, the electrocatalytic activity of Pd-NrGO hybrid material was accessed by cyclic voltammetry in presence of ethanol to evaluate its applicability in direct-ethanol fuel cells (DEFCs). The Pd-NrGO catalyst presented higher electro active surface area (∼6.3 m2 g-1) for ethanol electro-oxidation when compared to Pd-rGO hybrids (∼3.7 m2 g-1). Despite the smaller catalytic activity of Pd-NrGO, which was attributed to the lower exfoliation rate of this material in relation to the Pd-rGO, Pd-NrGO showed to be very promising and its catalytic activity can be further improved by tuning the synthesis parameters to increase the exfoliation rate.

Direct laser writing of micro-supercapacitors on thick graphite oxide films and their electrochemical properties in different liquid inorganic electrolytes.

In this article we demonstrate a simple approach to fabricate interdigitated in-plane electrodes for flexible micro-supercapacitors (MSCs). A nanosecond ultraviolet laser treatment is used to reduce and pattern the electrodes on thick graphite oxide (GO) freestanding films. These laser-treated regions obtained by direct writing provide the conducting channels for electrons in the capacitors. The electrochemical performance of the MSCs was evaluated in the presence of two different electrolytes and they exhibit characteristics of nearly electrical double layer capacitors. The MSCs have areal capacitances as 2.40, 2.23 and 1.62µF/cm2 for NaOH, Na2SO4 and KCl electrolytes respectively, for measurements performed at the scan rate of 50mV/s. They retain ∼93.1% of their initial capacitances after 3500 cycles (scan rate=80mV/s) in NaOH electrolyte. The proposed laser treatment approach enables facile and fast fabrication of flexible MSCs without the need for tedious processing methods such as photolithographic micro-patterning and deposition of porous carbon or metallic current collectors.

Triboelectric effect as a new strategy for sealing and controlling the flow in paper-based devices.

We reported here for the first time that triboelectric charges on PET sheets can be used to seal and control the flow rate in paper-based devices. The proposed method exhibits simplicity and low cost, provides reversible sealing and minimizes the effect of sample evaporation.