Copper-Doped Cobalt Spinel Electrocatalysts Supported on Activated Carbon for Hydrogen Evolution Reaction

The development of electrocatalysts based on the doping of copper over cobalt spinel supported on a microporous activated carbon has been studied. Both copper–cobalt and cobalt spinel nanoparticles were synthesized using a silica-template method. Hybrid materials consisting of an activated carbon (AC), cobalt oxide (Co3O4), and copper-doped cobalt oxide (CuCo2O4) nanoparticles, were obtained by dry mixing technique and evaluated as electrocatalysts in alkaline media for hydrogen evolution reaction. Physical mixtures containing 5, 10, and 20 wt.% of Co3O4 or CuCo2O4 with a highly microporous activated carbon were prepared and characterized by XRD, TEM, XPS, physical adsorption of gases, and electrochemical techniques. The electrochemical tests revealed that the electrodes containing copper as the dopant cation result in a lower overpotential and higher current density for the hydrogen evolution reaction.This research was funded by MINECO and FEDER (MAT2016-76595-R)

Synergistic relationship between the three-dimensional nanostructure and electrochemical performance in biocarbon supercapacitor electrode materials

A novel study presented herein correlates the multidimensional morphology with the electrochemical performance of activated bio-carbon materials, for supercapacitor devices over multiple length scales. The optimization of the potassium hydroxide (KOH)/cellulose ratio for supercapacitor electrode materials is related to morphological characteristics and corresponding electrochemical performance, as described in terms of porosity, specific surface area, specific capacitance and electrochemical impedance. KOH/cellulose samples with ratios 0.5 : 1 and 1 : 1 exhibited the best performance, characterized by a hierarchal porous network structure, high surface area and low cell resistance. Compared with the rest of the manufactured samples and commercial activated carbons, Ketjen Black (KB), Norit activated carbon (NAC) and bead-shaped activated carbon (BAC), the former two samples showed better results in three-electrode systems and coin cells, with specific gravimetric capacitances as high as 187 F g−1 at a current density of 1 A g−1. The high performance is attributed to the morphology of the samples that constituted a combination of micro-, meso- and macroporosity which consequently gave high specific surface area, high porosity, low cell resistance and high specific capacitance. This further corroborates the structure-performance relationship observed in the author's model KOH/cellulose system, highlighting that the work can be extended to other similar systems. It is clear that the three-dimensional nanostructure of a material must be understood in its entirety in order to optimize the electrochemical performance

Activated Carbons Prepared through H3PO4-Assisted Hydrothermal Carbonisation from Biomass Wastes: Porous Texture and Electrochemical Performance

Hydrothermal treatment of biomass in the presence of phosphoric acid is proposed for the production of activated carbons (ACs). Interestingly, H3PO4 promotes the fixation of carbon atoms in the solid during hydrothermal treatment, which renders higher preparation yields than those of the conventional impregnation method. Upon carbonisation of the resulting hydrochars at 450 °C, a notable development of porosity is achieved by using a low amount and concentration of phosphoric acid; these conditions are not adequate for conventional activation. The viability of this process for the sustainable production of ACs has been successfully checked in four biomasses of different composition and structures, and ACs of surface areas above 2000 m2 g−1 and tuneable pore size distribution have been obtained. Electrochemical characterisation of ACs prepared at 750 °C in 1 m H2SO4 demonstrates that capacitances of approximately 150 F g−1 with acceptable rate performance can be obtained through this simple method.This study was supported by the Ministry of Economy and Competitiveness (MINECO) of Spain (CTQ2015-66080-R MINECO/FEDER, MAT2013-42007-P, JCI-2012-12664) and Generalitat Valenciana (GRISOLIA/2014/029, PROMETEO/2013/038 and PROMETEOII/2014/010)