The study of the electrochemical catalyst conversion of renewable electricity and carbon oxides into chemical fuels attracts a great deal of attention by different researchers. The main role of this process is in mitigating the worldwide energy crisis through a closed technological carbon cycle, where chemical fuels, such as hydrogen, are stored and reconverted to electricity via electrochemical reaction processes in fuel cells. The scientific community focuses its efforts on the development of high-performance polymeric membranes together with nanomaterials with high catalytic activity and stability in order to reduce the platinum group metal applied as a cathode to build stacks of proton exchange membrane fuel cells (PEMFCs) to work at low and moderate temperatures. The design of new conductive membranes and nanoparticles (NPs) whose morphology directly affects their catalytic properties is of utmost importance. Nanoparticle morphologies, like cubes, octahedrons, icosahedrons, bipyramids, plates, and polyhedrons, among others, are widely studied for catalysis applications. The recent progress around the high catalytic activity has focused on the stabilizing agents and their potential impact on nanomaterial synthesis to induce changes in the morphology of NPs.

Proton Exchange Membrane Fuel Cells (PEMFCs): Advances and Challenges

Graphene oxide (GO) has attracted substantial interest in various fields of science and technology, owing to its remarkable mechanical, electrical and optical properties. It is prepared using the modified Hummers' method and employed as a precursor for the fabrication of graphene-based nanostructure materials. The facile synthesis of reduced graphene oxide and surface-modified GO using GO offers extensive opportunities in analytical chemistry. The surface modification of GO is realized via elemental doping and covalent and non-covalent bonding. It results in the functionalization of GO with different groups such as C–N, N N, N–H, and C–O–C. GO-based sensor technologies are extensively applied to identify numerous trace level analytes. These fluorescent, and electrochemical sensors are utilized primarily for detecting organic, inorganic, and biomolecules and for humidity sensing and bioimaging. The present review provides a holistic summary of not only the important literary aspects associated with GO but also the diverse practical applications of GO-based analytical strategies for the assaying of various target molecules.

Surface modifications and analytical applications of graphene oxide: A review

An overview of proton exchange membranes for fuel cells: Materials and manufacturing

Fuel cells are among the promising sources of clean energy, considering the low costs, low acoustical pollution, and the high-energy conversion. The remarkable features of graphene and its derivatives have triggered research studies on their applications in PEMFCs. PEMFCs still face some operational challenges for large-scale applications, including high costs, low proton conductivities at high temperatures, mechanical/thermal stabilities, and high fuel crossover. The unique characteristics of graphene-based materials, i.e., high electrochemical stability, good mechanical strength, large surface area, and excellent thermal stability, have been exploited in PEMFCs. This review discusses the potential role of graphene and graphene oxide (GO) in the membranes’ structural modifications, and utilization of polymer matrices such as SPEEK, PBI, PANI, SPAES, Nafion, and PVA polymers. The synthesis/functionalization of GO has been investigated with novel composite membranes and mechanisms involved in the enhancements of proton conductions, water uptakes, IECs, and power densities. Graphene materials showed excellent dispersion in solvents and alteration of membrane morphologies. The preceding properties are attributed to the formation of oxygen-based functional groups in GO nano-layers. The incorporation of graphene in other fuel cells, i.e., direct methanol fuel cells and biofuel cells, has exhibited commendable performance and appeared promising for commercial applications, especially with the reduction of fuel crossover. 

Recent developments in graphene and graphene oxide materials for polymer electrolyte membrane fuel cells applications

High-pressure PEM water electrolyser: A review on challenges and mitigation strategies towards green and low-cost hydrogen production

Sulfonated graphene oxide as an inorganic filler in promoting the properties of a polybenzimidazole membrane as a high temperature proton exchange membrane

An overview on the development of nanofiber-based as polymer electrolyte membrane and electrocatalyst in fuel cell application

One of the barriers to the large-scale commercialization of proton exchange membrane fuel cells (PEMFCs) is the high-priced of noble metals such as platinum (Pt). Therefore, in this paper, bimetallic electrocatalyst FeCo supported nitrogen-doped reduced graphene oxide (FeCo-NG) for oxygen reduction reaction (ORR) is proposed and has been successfully prepared through annealing of a mixture containing Fe, Co salts, dicyandiamide (DCDA) and graphene oxide (GO). The starting material GO appeared to be in multilayer sheets through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis. Due to the high annealing temperature and the absence of the surfactant, agglomeration of FeCo nanoparticles was observed from the morphology analysis. The macrostructure size of the metals particles was observed to be increased over temperature. As the temperature increases, the agglomeration gets more intense because of the increased of van der Waals cohesive forces between the nanoparticles. In addition, the weak electrostatic interaction between the metal cations with the nitrogen and the GO sheets could also be the cause of the agglomeration. The weak electrostatic interaction caused the nanoparticles (Fe and Co) not attracted onto the GO sheets thus inhibit the reduction of FeCo and GO to occur in situ simultaneously. It is believed that the agglomeration of the electrocatalyst FeCo-NG could results to poor electrocatalytic activity of PEMFC.

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Morphological Studies on the Agglomeration of FeCo Supported Nitrogen-doped Reduced Graphene Oxide Catalyst Prepared at Varying Annealing Temperature

Direct formic acid fuel cells (DFAFCs) have become an important technology and a clean energy source for various applications. However, some drawbacks in DFAFC applications, such as sluggish kinetics of formic acid oxidation (FAO) reaction at the anodic side, significantly affect DFAFC performance. An excellent catalyst, platinum (Pt), is very effective and performs excellently in FAO, but it is expensive and tends to form carbon monoxide-poisoning species on the catalyst surface. Therefore, new strategies must be developed to overcome problems related to Pt and simultaneously reduce or replace the use of Pt catalysts. This review paper covers the electrocatalytic activities of platinum and palladium (Pd)-based catalysts, which are commercial catalysts and effective for FAO and DFAFC applications. In this paper, the current progress of electrocatalyst development for anodic FAO and DFAFC applications using commercial Pt and Pd catalysts is presented, focusing on the understanding of Pt and Pd catalytic activities with the addition of alloys, metallic metals, trimetallic/tetrametallic metals, transition metals, and metal oxides. Highly potential nanostructured carbon catalyst supports (graphene-based materials, carbon nanotubes, carbon nanofibers, and graphitic carbon nitride) for FAO and DFAFC applications are also discussed. This review article also examines the literature related to Pt and Pd electrocatalysts on the synthesis routes, electrochemical conditions, and fuel cell performance within 10 years from 2013 until 2023. The challenges and strategies for electrocatalyst commercialization in the field are discussed at the end of the paper. 

Yusra Nadzirah Yusoff

Papers

Sulfonated graphene oxide as an inorganic filler in promoting the properties of a polybenzimidazole membrane as a high temperature proton exchange membrane

An overview on the development of nanofiber-based as polymer electrolyte membrane and electrocatalyst in fuel cell application

Morphological Studies on the Agglomeration of FeCo Supported Nitrogen-doped Reduced Graphene Oxide Catalyst Prepared at Varying Annealing Temperature

Electrocatalytic activities of platinum and palladium catalysts for enhancement of direct formic acid fuel cells: An updated progress

Fabrication of hybrid tin oxide‐cellulose nanocomposite as the flexible and thin supercapacitor