Electrochemical splitting of water to produce oxygen (O) and hydrogen (H) through a cathodic hydrogen evolution reaction (HER) and an anodic oxygen evolution reaction (OER) is a promising green approach for sustainable energy supply. Here we demonstrated a porous nickel-copper phosphide (NiCuP) nano-foam as a bifunctional electrocatalyst for highly efficient total water splitting. Prepared from a bubble-templated electrodeposition method and subsequent low-temperature phosphidization, NiCuP has a hierarchical pore structure with a large electrochemical active surface area. To reach a high current density of 50 mA cm, it requires merely 146 and 300 mV with small Tafel slopes of 47 and 49 mV dec for HER and OER, respectively. The total water splitting test using NiCuP as both the anode and cathode showed nearly 100% Faradic efficiency and surpassed the performances of electrode pairs using commercial Pt/C and IrO catalysts under our test conditions. The high activity of NiCuP can be attributed to (1) the conductive NiCu substrates, (2) a large electrochemically active surface area together with a combination of pores of different sizes, and (3) the formation of active Ni/Cu oxides/hydroxides while keeping a portion of more conductive Ni/Cu phosphides in the nano-foam. We expect the current catalyst to enable the manufacturing of affordable water splitting systems.

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With the aid of cold energy from regasification of liquefied natural gas (LNG), freeze desalination (FD) is an emerging technology for seawater desalination because of its low energy characteristics and insensitivities to fouling problems. This work aims to investigate the major operating parameters of FD such as coolant temperature, freezing duration, supercooling, seeding, agitation, crystallizer material and subsequent washing procedure on ice production and water quality. It was found that the optimal freezing duration per batch was 1 h for an iron crystallizer and 1.5 h for a glass crystallizer. The optimal coolant temperature should be around -8 °C. The optimal amount of washing water to clean the raw ice was about 50 wt% of the raw ice. Over 50 wt% of the feed could be recovered as raw ice within 1 h, which means an overall ice recovery rate of higher than 25% (of the original seawater), considering the consumption of washing water. Both artificial and real seawater were tested under the optimized conditions. The total dissolved solid in the product ice was around 300 ppm, which met the World Health Organization (WHO) potable water salinity standard of 500 ppm. Therefore, the process parameters optimized in this study can be directly used for the freeze desalination of seawater.

Management of produced water from shale gas production is a global challenge. Vacuum membrane distillation (VMD) is considered a promising solution because of its various advantages. However, low-surface-tension species in produced water can easily deposit on the membrane surface and cause severe fouling or wetting problems. To solve the problems, an omniphobic polyvinylidene difluoride (PVDF) hollow-fiber membrane has been developed via silica nanoparticle deposition followed by a Teflon AF 2400 coating in this study. The resultant membrane shows good repellency toward various liquids with different surface tensions and chemistries, including water, ethylene glycol (EG), cooking oil, and ethanol. It also exhibits stable performance in 7 h VMD tests with a feed solution containing up to 0.6 mM of sodium dodecyl sulfate (SDS). In addition, the effects of surface energy and surface morphology as well as nanoparticle size on membrane omniphobicity have been systematically investigated. This work may provide valuable guidance to molecularly design omniphobic VMD membranes for produced water treatment.

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