The oxygen reduction reaction (ORR) is the core process - but also the bottleneck - for the cathode reaction of energy-conversion devices like certain types of fuel cells and metal-air batteries. Nanocarbon materials are very promising alternatives for the noble metal catalysts, especially platinum, that have been used to boost this reaction. New work comprehensively reviews and correlates activity origins of nanocarbon-based ORR electrocatalysts, considering the dopants, edges, and defects. Specific doping at defective edges is expected to render practical applications for metal-free nanocarbon electrocatalysts.
Methanol fuel cells are widely considered as a potential source of future energy due to the usage of methanol as a liquid fuel; simplicity in operation; higher energy density of methanol fuel; high power density obtained etc. However their commercialization is greatly hindered by methanol crossover taking place in the membrane area of fuel cells, leading to short circuits and greatly affecting overall performance. By using two-dimensional (2D) materials - graphene and hexagonal boron nitride (hBn) - in methanol fuel cell systems, researchers now have overcome this bottleneck.
Flexible thermoelectric generators that are capable of producing electricity out of a temperature difference could have many applications in consumer and medical electronics. However, conventional thermoelectric materials are rigid and brittle and don't lend themselves to be used with flexible devices. Researchers have now demonstrated a flexible paper-based devices can be easily stacked or efficiently folded and cut through origami and kirigami techniques so that it is possible to achieve higher power densities. This allows for enough electricity to be generated to supply low-power systems, especially in applications where flexibility is advantageous, such as robotics, cybernetics, wearable devices or bio-integrated systems.
Lithium-sulfur (Li-S) batteries, which employ sulfur as cathode and metallic lithium as anode materials, have been extensively studied as promising alternatives to the widely used lithium-ion batteries because - theoretically - they can render 3-6 times higher energy density than conventional lithium-ion batteries. However, due to the intrinsic insulating nature of the active material (sulfur and lithium sulfide), Li-S batteries have suffered from low utilization of sulfur and thus low energy density. In new work, researchers have designed coaxial nanotubes with adjustable content of MnO2 to encapsulate sulfur as a high-performance cathode for Li-S batteries.
Efficient water splitting for large-scale, industrial applications requires highly active, low cost, and robust catalysts. Motivated by this challenge, enormous efforts have been devoted to developing cost-efficient alternatives including sulfides, selenides, phosphides, and many other nonprecious transition metal compounds. Now, scientists have shown for the first time that metals or metal hydroxides can be rapidly converted into phosphides at low temperature using a newly developed plasma-assisted route.
Researchers have demonstrated a fully stretchable energy harvester for thermal waste, which is very simple to fabricate and uses inexpensive substrate materials such polymers or paper. Thermoelectric generators (TEGs) promise a cheap and pragmatic way to obtain energy out of waste heat. The novelty of this work is to effectively integrate the high-performance of inorganic thermoelectric materials with the mechanical advantages of affordable organic materials (polymers, paper) and the use of innovative geometries that can be inherently stretched (spirals, helixes).
Oxygen evolution reaction (OER) is the core process - but also the bottleneck - in many energy devices such as metal-air batteries and water-splitting techniques, calling for new insights in rational design of OER electrocatalysts. The perovskite family exhibits superb OER reactivity, but its poor conductivity remains a big problem, not to mention that the morphology of perovskite oxides is hard to control. In situ hybridization of perovskite oxides with conductive frameworks is an efficient strategy to solve these problems, as researchers report in new work.
Solar cells absorb incoming sunlight and convert a part of photon energy into electricity. The remainder of photon energy is dissipated as heat. Although the idea is rather counter-intuitive, 'reverse solar cell' systems can also generate electric power by emitting rather than absorbing photons. Such systems - known as thermoradiative cells - generate voltage and electric power via non-equilibrium thermal radiation of infrared photons. Thermoradiative cells offer an opportunity to generate clean energy by harvesting radiation from largely untapped terrestrial thermal emission sources, potentially including the Earth itself.