Methanol-Tolerant M–N–C Catalysts for Oxygen Reduction Reactions in Acidic Media and Their Application in Direct Methanol Fuel Cells

Abstract

Direct methanol fuel cells (DMFCs) are emerging technologies for the electrochemical conversion of the chemical energy of a fuel (methanol) directly into electrical energy, with a low environmental impact and high efficiency. Yet, before this technology can reach a large-scale diffusion, specific issues must be solved, in particular, the high cost of the cell components. In a direct methanol fuel cell system, high capital costs are mainly derived from the use of noble metal catalysts; therefore, the development of low-cost electro-catalysts, satisfying the target requirements of high performance and durability, represents an important challenge. The research is currently addressed to the development of metal-nitrogen-carbon (M-N-C) materials as cheap and sustainable catalysts for the oxygen reduction reaction (ORR) in an acid environment, for application in polymer electrolyte fuel cells fueled by hydrogen or alcohol. In particular, this mini-review summarizes the recent advancements achieved in DMFCs using M-N-C catalysts. The presented analysis is restricted to M-N-C catalysts mounted at the cathode of a DMFC or investigated in rotating disk electrode (RDE) configuration for the ORR in the presence of methanol in order to study alcohol tolerance. The main synthetic routes and characteristics of the catalysts are also presented.

Anionic Exchange Membrane for Photo-Electrolysis Application

“…Efficiency and durability to produce pure H 2 by photo-electrolysis may be improved by employing a solid polymer-electrolyte between the electrodes as a gas separator. This separation for polymer-electrolyte membrane fuel cells (PEMFCs) and their subcategories [ 19 , 20 , 21 , 22 ] has been known for many years whereas the employment of a solid-membrane electrolyte has been less studied for PEC applications [ 23 , 24 ]. Its implementation in a cost-effective tandem PEC architecture, able to capture a significant portion of the solar irradiation, is structured as photoanode/membrane/photocathode and the working mechanism has been discussed in detail in some recent work [ 25 , 26 ].…”

Performance Improvement in Direct Methanol Fuel Cells by Using CaTiO3-δ Additive at the Cathode

“…Several approaches of the last decade were explored with the aim to reduce cost and improve ORR in the presence of permeated methanol [6][7][8][9][10][11][12]. Pt-alloys exhibit enhanced electrocatalytic activity for the ORR compared to Pt alone [13,14], due to both electronic factors (i.e., higher level of Pt d-band vacancy) and geometric effects (i.e., optimized Pt-Pt interatomic distance).…”

New Insights into Properties of Methanol Transport in Sulfonated Polysulfone Composite Membranes for Direct Methanol Fuel Cells

“…State-of-the-art membranes for DMFCs are based on perfluorosulfonic acid membranes (PFSAs), such as Nafion ® membranes, which are used successfully in DMFCs operating with a low methanol concentration (1 or 2 M) at the anode [ 9 , 10 ]. Operation with high methanol concentration produces high methanol permeation through the membrane, from the anode to the cathode, leading to a loss of fuel efficiency in the DMFC together with a mixed potential at the cathode with a consequent decrease of cell voltage, unless a cathodic catalyst tolerant to the alcohol is used [ 9 , 11 , 12 ]. Consequently, the research on new proton exchange membranes is mandatory not only to reduce the methanol permeation while maintaining a good proton conductivity, but also to reduce the cost compared to the expensive PFSA membranes.…”