Carbon nanotube sponges are synthesized by chemical vapor deposition, in which nanotubes are self‐assembled into a three‐dimensionally interconnected framework. The sponges are very light, highly porous, hydrophobic in pristine form, and can be elastically and reversibly deformed into any shape. The sponges can float on water surfaces and absorb large‐area spreading oil films (see images), suggesting promising environmental applications.

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Electrochemical water splitting is a promising method for storing light/electrical energy in the form of H fuel; however, it is limited by the sluggish anodic oxygen evolution reaction (OER). To improve the accessibility of H production, it is necessary to develop an efficient OER catalyst with large surface area, abundant active sites, and good stability, through a low-cost fabrication route. Herein, a facile solution reduction method using NaBH as a reductant is developed to prepare iron-cobalt oxide nanosheets (Fe Co -ONSs) with a large specific surface area (up to 261.1 m g ), ultrathin thickness (1.2 nm), and, importantly, abundant oxygen vacancies. The mass activity of Fe Co -ONS measured at an overpotential of 350 mV reaches up to 54.9 A g , while its Tafel slope is 36.8 mV dec ; both of which are superior to those of commercial RuO , crystalline Fe Co -ONP, and most reported OER catalysts. The excellent OER catalytic activity of Fe Co -ONS can be attributed to its specific structure, e.g., ultrathin nanosheets that could facilitate mass diffusion/transport of OH ions and provide more active sites for OER catalysis, and oxygen vacancies that could improve electronic conductivity and facilitate adsorption of H O onto nearby Co sites.

Defects derived by the removal of heteroatoms from graphene are demonstrated, both experimentally and theoretically, to be effective for all three basic electrochemical reactions, e.g., oxygen reduction (ORR), oxygen evolution (OER), and hydrogen evolution (HER). Density function theory calculations further reveal that the different types of defects are essential for the individual electrocatalytic activity for ORR, OER, and HER, respectively.

Herein, the authors demonstrate a heterostructured NiFe LDH-NS@DG10 hybrid catalyst by coupling of exfoliated Ni-Fe layered double hydroxide (LDH) nanosheet (NS) and defective graphene (DG). The catalyst has exhibited extremely high electrocatalytic activity for oxygen evolution reaction (OER) in an alkaline solution with an overpotential of 0.21 V at a current density of 10 mA cm , which is comparable to the current record (≈0.20 V in Fe-Co-Ni metal-oxide-film system) and superior to all other non-noble metal catalysts. Also, it possesses outstanding kinetics (Tafel slope of 52 mV dec ) for the reaction. Interestingly, the NiFe LDH-NS@DG10 hybrid has also exhibited the high hydrogen evolution reaction (HER) performance in an alkaline solution (with an overpotential of 115 mV by 2 mg cm loading at a current density of 20 mA cm ) in contrast to barely HER activity for NiFe LDH-NS itself. As a result, the bifunctional catalyst the authors developed can achieve a current density of 20 mA cm by a voltage of only 1.5 V, which is also a record for the overall water splitting. Density functional theory calculation reveals that the synergetic effects of highly exposed 3d transition metal atoms and carbon defects are essential for the bifunctional activity for OER and HER.