A Review of Proton Conductivity in Cellulosic Materials

Abstract

Cellulose is derived from biomass and is useful in a wide range of applications across society, most notably in paper and cardboard. Nanocellulose is a relatively newly discovered variant of cellulose with much smaller fibril size, leading to unique properties such as high mechanical strength. Meanwhile, electrochemical energy conversion in fuel cells will be a key technology in the development of the hydrogen economy, but new lower cost proton exchange membrane (PEM) materials are needed. Nanocellulose has emerged as a potential candidate for this important application. In this review we summarize scientific developments in the area of cellulosic materials with special emphasis on the proton conductivity, which is the most important parameter for application in PEMs. We cover conventional cellulose and nanostructured cellulose materials, polymer composites or blends, and chemically modified cellulose. These developments are critically reviewed, and we identify interesting trends in the literature data. Finally, we speculate on future directions for this field.

“Artificial Wood” Lignocellulosic Membranes: Influence of Kraft Lignin on the Properties and Gas Transport in Tunicate-Based Nanocellulose Composites

“…However, the result is relevant because there is a strong interest in utilizing widely available biopolymers such as cellulose and lignin in a variety of applications. In respect to gas permeability, nanocellulose is often mentioned as a good gas barrier material, and therefore is suggested to be used for sustainable packaging or other applications [ 1 , 3 , 10 , 11 , 12 , 43 , 44 , 45 ]. The results of our work show that this cannot be a default assumption, as the gas barrier will strongly depend on the material micromorphology and crystallinity.…”

“…Nanocellulose is a form of cellulosic material that can be obtained from the smallest organisms (i.e., bacteria) to the largest high plants (i.e., trees). Due to its combination of high mechanical strength and low density, it is expected to be used in a variety of emerging applications, such as in environmentally friendly composite materials, films, coatings, and membranes in the food and pharmaceutical industries and for energy applications [ 1 , 2 , 3 ]. Taking into their account natural origin, renewable character, and biodegradability, biomass-derived materials are an important research direction, with the aim of substituting the multitude of materials obtained from fossil fuels.…”

A Review of Recent Developments and Advanced Applications of High-Temperature Polymer Electrolyte Membranes for PEM Fuel Cells

“…To measure the proton conductivity in liquid water or at relative humidity lower than 100%, the cell is placed in a distilled deionized water or a humid chamber with controlled humidity (thermos-controlled humid chamber), respectively. In-plane conductivity can be calculated as follows [214][215][216][217]:…”

“…To determine the resistance, the high-frequency intercept of the impedance with the real axis should be used. The following equation can be used for the through-plane conductivity calculations [214][215][216]:…”

Proton Conductive, Low Methanol Crossover Cellulose-Based Membranes

“…The hydroxyl group’s vigorous inter and intrachain interactions (hydrogen bonding) are the reason for the structure to be rigid, closely packed, and exceedingly complicated [ 24 ]. Cellulose has been widely investigated as a potential electrolyte membrane for DMFC [ 25 ], either in its pristine form, blended with other polymers [ 26 ], or chemically modified [ 27 ]. For example, introducing a proton-donating acid groups method was followed by crosslinking cellulose fibers with sulfonic acid linkers to enhance the proton conductivity [ 28 ].…”