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Platinum and platinum-based catalysts are some of the most effective catalysts used in fuel cells. However, electrocatalysts used for direct liquid fuel cells (DLFCs) and electrolyzers are high cost and suffer from several other problems, thus hindering their commercialization as power sources to produce clean energy. Common issues in electrocatalysts are low stability and durability, slow kinetics, catalyst poisoning, high catalyst loading, high cost of the catalytic materials, poisoning of the electrocatalysts, and formation of intermediate products during electrochemical reactions. The use of catalyst supports can enhance the catalytic activity and stability of the power sources. Thus, nickel foam and graphene foam with 3D structures have advantages over other catalyst supports. This paper presents the application of nickel foam and graphene foam as catalyst supports that enhance the activities, selectivity, efficiency, specific surface area, and exposure of the active sites of DLFCs. Selected recent studies on the use of foam in electrolyzers are also presented.

Methanol crossover affects the performance of a direct methanol fuel cell (DMFC). To overcome this problem, this study introduced a modified microporous diffusion layer (MPL) with addition of titanium dioxide (TiO 2 ) to the carbon nano-fibre (CNF) and carbon black (CB) material at the anode side of DMFC. The main objectives of this work were to present a surface characterization of the modified MPL via scanning electron microscopy (SEM) and discussed the detailed mechanism on the drop of the power density due to increment of methanol concentration. Secondly, this work also tested the performance and stability of the modified MPL. The SEM imaging showed a reduced surface crack at the anode diffusion layer in CB + TiO 2 , the pore network improved on the mixture of CNF-TiO 2 . Electrochemical impedance spectroscopy (EIS) showed that TiO 2 has low resistance and helps to reduce the resistance when added to the CNF and CB. These findings showed that the mixture of TiO 2 with CNF and CB presented a good effect in reducing the methanol crossover by presenting the lowest percentage for stability drop as 0.31% and 1.37% compared to other researchers. It also improved the stability of the DMFC power output over the long-term performance test. Highlights:• This study presents a surface characterization of the modified MPL of TiO 2 -CNF-CB • It also discusses in detail the mechanism on the power density drop due to increment of methanol concentration • This study will also test the performance and stability of the modified MPL.• The results show that the mixture of TiO 2 -CNF-CB improved the stability of the DMFC K E Y W O R D S anode diffusion layer, carbon nano-fibre, direct methanol fuel cell, titanium dioxide

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BACKGROUNDDirect ethanol fuel cells (DEFC) need fillers to mitigate the issue of ethanol crossing over from the anode to the cathode, which lowers performance. Therefore, this study developed calcium carbonate (CaCO3) from chicken eggshells as a filler in a Nafion composite membrane for DEFC. Three cluster models of CaCO3 filler were developed, namely (CaCO3)2, (CaCO3)3, and (CaCO3)4, to form the Nafion composite membranes. The properties of composite membranes, such as proton conductivity, ethanol permeability, and selectivity, were studied using the molecular dynamics method. In addition, the three main factors influencing the composite membranes’ properties were analyzed in this study; these were cluster size of CaCO3, mass loading of the filler, and ethanol concentration.RESULTSThe results show that filler has reduced proton conductivity and ethanol permeability in the DEFC application compared to the Nafion membrane. However, the selectivity is used as a trade‐off between ion conductivity and ethanol permeability in the composite membrane, thus requiring a suitable size structure and mass loading to balance the high ion conductivity rate and reduce the ethanol permeability rate. The composite membrane C‐(CaCO3)4, which has a large cluster size in this study, shows that it is necessary to restrict ethanol permeability at a high ethanol concentration of 5 mol L−1. However, the structure size in cluster B – (CaCO3)3 – can reduce ethanol permeability but requires high mass loading by 5 wt%. Analysis of variance showed significant values for ion conductivity, ethanol permeability, and selectivity responses.CONCLUSIONCaCO3 successfully reduced ethanol crossover in DEFC, with all three composite membranes being suitable for use at low ethanol concentrations. However, specific size structure and mass loading are required to overcome ethanol crossover at high ethanol concentration. © 2023 Society of Chemical Industry (SCI).