Cost-Effective Biobased Proton Exchange Membranes Fabricated Mainly from Modified Sodium Alginate and Diatomite

The proton exchange membranes mainly derived from natural algal resources (APEMs) with low cost and environmental friendliness were constructed by combining the modified sodium alginate and porous diatomite, as well as cross-linking. APEMs showed good thermal, dimensional, and mechanical stability, as well as excellent methanol barrier due to the formation of three-dimensional network structure. At the same time, the introduction of a large number of acidic groups and the construction of more proton transfer channels made APEMs have good proton conductivity. The membrane containing 4% additive showed the best adaptation to DMFC due to its high proton conductivity (0.0507 S cm–1) and low methanol diffusion coefficient (2.45 × 10–7 cm2 s–1). Therefore, it exhibited the highest selectivity of 2.1 × 105 Ss cm–3 and the best maximum power density of 65.0 mW cm–2. This work provides a unique perspective for the design of high-performance and low-cost PEMs, which is of great significance for expanding the types of PEMs, effectively utilizing natural resources, protecting the environment, and maintaining social sustainability.