Microbial fuel cell (MFC) technology has the potential to become a major renewable energy resource by degrading organic pollutants in wastewater. The performance of MFC directly depends on the kinetics of the electrode reactions within the fuel cell, with the performance of the electrodes heavily influenced by the materials they are made from. A wide range of materials have been tested to improve the performance of MFCs. In the past decade, carbon-based nanomaterials have emerged as promising materials for both anode and cathode construction. Composite materials have also shown to have the potential to become materials of choice for electrode manufacture. Various transition metal oxides have been investigated as alternatives to conventional expensive metals like platinum for oxygen reduction reaction. In this review, different carbon-based nanomaterials and composite materials are discussed for their potential use as MFC electrodes.

Clean water supply in off-grid locations remains a stumbling stone for socio-economic development in remote areas where solar energy is abundant. In this regard, several technologies have already introduced various solutions to the off-grid freshwater predicament; however, most of them are either costly or complex to operate. Nonetheless, photothermal membrane distillation (PMD) has emerged as a promising candidate with great potential to be autonomously driven by solar energy. Instead of using energy-intensive bulk feed heating in conventional MD systems, PMD membranes can directly harvest the incident solar light at the membrane interface as an alternative driving energy resource for the desalination process. Because of its excellent photothermal properties and stability in ionic environments, herein, Ti 3 C 2 T x MXene was coated onto commercial polytetrafluoroethylene (PTFE) membranes to allow for a self-heated PMD process. An average water vapor flux of 0.77 kg/m 2 h with an excellent temporal response under intermitting lighting and a photothermal efficiency of 65.3% were achieved by the PMD membrane under one-sun irradiation for a feed salinity of 0.36 g/L. Naturally, the efficiency of the process decreased with higher feed concentrations due to the reduction of the evaporation rate and the scattering of incident sunlight toward the membrane photothermal surface, especially at rates above 10 g/L. Notably, with such performance, 1 m 2 of the MXene-coated PMD membrane can fulfill the recommended daily potable water intake for a household, that is, ca. 6 L/day.

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At present, around 25% of water desalination processes are based on distillation. Similar to classical distillation, membrane distillation is a phased-change process in which a hydrophobic membrane separates two phases. Membrane distillation is considered an emerging player in the desalination, food processing and water treatment market. Due to its high salt rejection, less fouling propensity, operating at moderate temperature and pressure, membrane distillation is considered as a future sustainable desalination technology. The distillation process is quite well known in desalination. However, membrane distillation emerged a few decades ago, and a thorough understanding is needed to adapt this technique in the near future. This review chapter introduces the classical distillation and membrane distillation as an emerging technology in the desalination arena. Heat and mass transfer and thermodynamics in membrane distillation, characteristics of the performance metrics of membrane distillation are also described. Finally, the performance evaluation of MD is presented. The possibility of using low-grade heat in membrane distillation allows it to integrate directly to solar energy and industrial waste heat.