Hydroelectric dams, such as the Kariba Dam on the Zambezi river (pictured), provide a significant and growing fraction of electricity generation in sub-Saharan Africa, but rainfall variability poses disruption risks. Conway et al. analyse rainfall variability across eastern and southern Africa and examine its impact on river basins for present and planned dams, uncovering supply risks and spatial interlinkages.

See Conway et al. and News & Views by Kling.

Metal–organic frameworks (MOFs) that conduct protons have potential as electrolytes in proton–exchange membrane fuel cells. Yang et al. report a highly proton–conducting MOF (represented here) that has 1D channels decorated with sulfonic acid sites that are involved in mediating proton conduction. The MOF is structurally flexible, which is suggested to allow retention of good proton conductivity in a range of humid atmospheres.

See Yang et al. and News and Views by Shimizu

Swimming like a solar cell

Lightweight, flexible and stretchable solar cells can be processed from some polymers and organic molecules. Jinno et al. expand on these mechanical capabilities and use ultrathin barrier layers to make the flexible solar cells stable in water. Making flexible solar cells washable multiplies their integration prospects into everyday objects.

See Jinno et al. 2, 780–785 (2017) and News and Views by Li & Brabec.

Evolving catalysts evolve hydrogen

Transition metal dichalcogenides (TMDs) can be used for electrocatalytic generation of hydrogen from water. Guided by computation, Liu et al. show that high electrocatalytic activity can be achieved on the basal planes — rather than the edge sites, which are more commonly associated with high activity — of certain layered TMDs such as tantalum disulfide. The activity improves during cycling due to evolution of the catalyst morphology.

See Liu et al. 2, 17127 (2017) and News and Views by Chirdon & Wu, article 17132.

Complementary contributions

The various wavelengths of the solar spectrum can be exploited for different functionalities. Davy et al. develop an organic solar cell that harvests near-ultraviolet photons to power an electrochromic device that controls how many photons go through a smart window in other wavelength ranges, adjusting both visible light and heat ingress.

See Davy et al. 2, 17104 (2017) and News and Views by Delia Milliron, article 17116.

Burning to compress

High loading of active materials at the cathode is essential to realise the high energy density potential of Li-S batteries, but conventional cathodes have a non-compact structure that severely limits the active material loading. Tan et al. report that by burning Li foils in a CS2 vapour, highly compact Li2S–graphene nanocapsules are obtained (represented here) that can be used in high-performing Li-S batteries.

See Tan et al. 2, 17090 (2017) and News and Views by Li & Chen, article 17096.

Time to change charging habits

When electric vehicles are charged has a significant impact on their carbon footprint, but electric vehicle charging is a repetitive behavior that can be difficult to change. Nicolson et al. find that people are more likely to engage with time-of-use energy tariff information in a tailored email emphasizing reductions in home-charging costs within the first three months of electric vehicle purchase, before habits are formed.

See Nicolson et al. 2, 17073 (2017) and News & Views by Deborah Roy, article 17077.

Traffic control in silicon

Back-contacted silicon solar cells with interdigitated passivated contacts have high efficiencies but are complex to manufacture. Tomasi et al. now report a simple process to self-align the two types of electronic contacts based on the surface-dependent crystalline growth of silicon and fabricate solar cells with a certified efficiency above 22%.

See Tomasi et al. 2, 17062 (2017).

Seawater source

There are huge amounts of uranium present in the oceans that could be used for nuclear fuel, but recovery methods suffer from low capacity and limited extraction rates. Liu et al. use a pulsed electric field to migrate uranyl ions to a polymer-functionalized electrode, where they deposit on the surface as uranium oxide (shown here). The uptake capacity and kinetics of the extraction are improved relative to conventional physicochemical methods.

See Liu et al. 2, 17007 (2017) and News & Views by Costas Tsouris, article 17022.

Additives work wonders

Lithium-metal batteries offer great potential for high-energy-density storage but suffer from limited charging capability and cycling stability. Zheng et al. report that by tuning a dual salt electrolyte composition with additives, the performance of lithium-metal batteries (whose working lithium electrode is shown here) can be significantly improved.

See Zheng et al. 2, 17012 (2017) and News and Views by Zheng & Wei, article 17029.

The costs of going solo

Energy storage coupled with solar panels is increasingly viewed as a way for homes to cut reliance on utilities. Exploiting data from real homes in Texas, USA, Fares and Webber investigate the impacts of solar energy storage, and find that although peak demand could be reduced, average annual consumption and emissions may actually increase.

See Fares and Webber 2, 17001 (2017) and News & Views by Eric Hittinger, article 17006.

Wet work for perovskites

Organometal-halide perovskites are well-known for their photovoltaic performance but also their instability towards moisture. Park et al. show that by exploiting dynamic equilibrium, methylammonium lead iodide can be used to photocatalytically evolve hydrogen from aqueous hydrogen iodide solutions, harnessing solar energy to produce storable chemicals rather than electricity as in solar cells.

See Park et al. 2, 16185 (2016) and News & Views by Peter Vesborg, article 16205.