Parallel Nanosheet Arrays for Industrial Oxygen Production.

According to the traditional nucleation theory, crystals in solution nucleate under thermal fluctuations with random crystal orientation. Thus, nanosheet arrays grown on a substrate always exhibit disordered arrangements, which impede mass transfer during catalysis. To overcome this limitation, here, we demonstrate stress-induced, oriented nucleation and growth of nanosheet arrays. A regularly self-growing parallel nanosheet array is realized on a curved growth substrate. During electrochemical oxygen production, the ordered array maintains a steady flow of liquids in the microchannels, suppressing the detrimental production of flow-blocking oxygen bubbles typical of randomly oriented nanosheet arrays. Controllable parallel arrays, fully covered fluffy-like ultrathin nanosheets, and amorphous disordered structures altogether enable full-scale design of hierarchical interfaces from the micro- to the atomic scale, significantly improving the otherwise sluggish kinetics of oxygen evolution toward industrial ultrafast production. Record-high ultrafast oxygen production of 135 L·min-1·m-2 with high working current of 4000 mA·cm-2 is steadily achieved at a competitively low cell voltage of 2.862 V. These results and related insights lay the basis for further developments in oriented nucleation and growth of crystals beyond classical nucleation approaches, with benefits for large-scale, industrial electrochemical processes as shown here for ultrafast oxygen production.

Graphene oxide bulk material reinforced by heterophase platelets with multiscale interface crosslinking.

Graphene oxide (GO) and reduced GO possess robust mechanical, electrical and chemical properties. Their nanocomposites have been extensively explored for applications in diverse fields. However, due to the high flexibility and weak interlayer interactions of GO nanosheets, the flexural mechanical properties of GO-based composites, especially in bulk materials, are largely constrained, which hinders their performance in practical applications. Here, inspired by the amorphous/crystalline feature of the heterophase within nacreous platelets, we present a centimetre-sized, GO-based bulk material consisting of building blocks of GO and amorphous/crystalline leaf-like MnO2 hexagon nanosheets adhered together with polymer-based crosslinkers. These building blocks are stacked and hot-pressed with further crosslinking between the layers to form a GO/MnO2-based layered (GML) bulk material. The resultant GML bulk material exhibits a flexural strength of 231.2 MPa. Moreover, the material exhibits sufficient fracture toughness and strong impact resistance while being light in weight. Experimental and numerical analyses indicate that the ordered heterophase structure and synergetic crosslinking interactions across multiscale interfaces lead to the superior mechanical properties of the material. These results are expected to provide insights into the design of structural materials and potential applications of high-performance GO-based bulk materials in aerospace, biomedicine and electronics.