Cobalt-Doped Ceria/Reduced Graphene Oxide Nanocomposite as an Efficient Oxygen Reduction Reaction Catalyst and Supercapacitor Material

Abstract

Design and development of highly active and durable oxygen reduction reaction (ORR) catalyst to replace Pt-and Pt-based materials are present challenges in fuel cell research including direct methanol fuel cells (DMFC). The methanol crossover and its subsequent oxidation at the cathode is another unwanted issue that reduces the efficiency of DMFC. Herein we report cobalt-doped ceria (Co-CeO 2 ) as a promising electrocatalyst with competent ORR kinetics mainly through a four-electron reduction pathway, and it surpasses Pt/C by a great margin in terms of stability and methanol tolerance. The Co-CeO 2 nanoparticles of diameter 4−7 nm were uniformly grown on reduced graphene oxide (rGO) by a facile single-step hydrothermal process. The assynthesized Co-CeO 2 nanoparticles/rGO nanocomposites are further demonstrated as active energy storage materials in supercapacitors, underscoring the importance of the studied materials in renewable energy industries.

Microwave‐Assisted Synthesis of ZnO–rGO Core–Shell Nanorod Hybrids with Photo‐ and Electro‐Catalytic Activity

“…Although the ZnO–rGO hybrid NRs cannot yet match the level of ORR performance shown by N‐GQD/graphene catalysts, our results are comparable to the ORR activity of rGO‐supported metal oxides, such as the ZnO@rGO materials reported by Sun et al . and Co‐doped Ceria/rGO nanocomposites reported by Parwaiz et al . Following the lead of the successful catalysts described above, we anticipate that the catalytic activity and durability of the ZnO–rGO hybrid NRs can be improved by incorporation of heteroatoms (such as nitrogen) into rGO and/or by doping the ZnO NPs with other transition metals.…”

“…prepared a PtCu@graphene quantum dot (GQD) composite which has better catalytic activity than commercial Pt black . In the presence of the GQDs, the ORR onset potential for the PtCu catalyst shifted in a positive direction, indicating that the ORR process occurs much more easily when using the hybrid . Similarly, in our system we also observed a positive shift in the half‐wave potential of 0.08 V on addition of rGO to ZnO.…”

Development of an Efficient Non‐Noble Metal Based Anode Electrocatalyst to Promote Methanol Oxidation Activity in DMFC

“…The current density value in the absence of methanol is 37.4 mA cm À 2 while in the presence of methanol the current density values for Co BTC MOF and their composites such as 1 wt%, 2 wt% and 5 wt% are118 mA cm À 2 , 130 mA cm À 2 , 125 mA cm À 2 and 115 mA cm À 2 respectively. Among all the prepared composites and Co BTC MOF, 1 wt% show high current density value and considered to be an [1,44,57,60,68,69] In order to understand the effect of change in scan rate values on current density of the prepared catalysts, the cyclic voltammetry experiments were performed at 2, 5, 10, 25 and 50 mV s À 1 in alkaline medium by selecting voltage window from À 0.1-0.7 V. Increase in current density due to maximum approach of electro active species toward electrode surface with corresponding increase in scan rate is evidently elaborated in Figure 7 a-d. [56,70] Linear relationship of (scan rate) 1/2 vs current density giving an idea about diffusion coefficient calculated by Randles Sevcik equation is shown in Figure 8. 1wt % rGO/Co BTC composite with paramount value of diffusion coefficient (0.26 x10 À 5 ) and R 2 value almost equal to 1 justify a diffusion controlled process to be followed in methanol oxidation process.…”

AgCoO2−Co3O4/CMC Cloudy Architecture as High Performance Electrodes for Asymmetric Supercapacitors

“…Supercapacitors can store charges either by ion adsorption phenomenon (electric double layer capacitor, EDLC) or fast Faradic reactions (pseudocapacitor) . Conventionally, carbonaceous materials (graphene, CNT, activated carbon) and pseudocapacitive materials (transition metal oxides and conducting polymers) serve as electrode materials in supercapacitors …”

“…[4] Conventionally, carbonaceous materials (graphene, CNT, activated carbon) and pseudocapacitive materials (transition metal oxides and conducting polymers) serve as electrode materials in supercapacitors. [5][6][7][8] Cobalt oxide (Co 3 O 4 ) has attracted special interest widely as an electrode material for supercapacitors owing to its multiple redox states (Co + , Co 2 + , Co 3 + , Co 4 + ), high theoretical capacitance (~3560 F g À 1 ), excellent thermal and electrochemical stability, etc. [9][10][11][12] Nevertheless, its poor conductivity (10 À 3 to 10 À 4 S cm À 1 ), low rate capability and limited availability (3 0 ppm in earth curst) restricts its commercialization as an electrode in supercapacitor applications .…”