We report the electrochemical reduction of CO2 at copper foams with hierarchical porosity. We show that both the distribution of products formed from this reaction and their faradaic efficiencies differ significantly from those obtained at smooth electropolished copper electrodes. We attribute these differences to be due to high surface roughness, hierarchical porosity, and confinement of reactive species. We provide preliminary evidence in support of these claims.

Sodium-ion batteries hold promise as an enabling technology for large-scale energy storage that is safer, less expensive, and lower environmentally impactful than their equivalent lithium-ion batteries. Reported herein is the one-pot hydrothermal synthesis, crystal structure, and electrochemical properties of a promising sodium-ion battery cathode material, an alluaudite phase of Na1.702Fe3(PO4)3. After ball milling and carbon coating, this material exhibits a reversible capacity of ∼140 mAh/g with good cycling performance (93% of the initial capacity is retained after 50 cycles) and excellent rate capability. This alluaudite compound and its method of preparation is a promising cathode for large-scale battery applications that are earth-abundant and sustainable.

Nanoreactors are material structures that provide engineered internal cavities that create unique confined nanoscale environments for chemical reactions. Crumpled graphene nanoparticles or "nanosacks" may serve as nanoreactors when filled with reactive or catalytic particles and engineered for a specific chemical function. This article explores the behavior of crumpled graphene nanoreactors containing nanoscale ZnO, Ag, Ni, Cu, Fe, or TiO2 particles, either alone or in combination, in a series of case studies designed to reveal their fundamental behaviors. The first case study shows that ZnO nanoparticles undergo rapid dissolution inside the nanoreactor cavity accompanied by diffusive release of soluble products to surrounding aqueous media through the irregular folded shell. This behavior demonstrates the open nature of the sack structure, which facilitates rapid small-molecule exchange between inside and outside that is a requirement for nanoreactor function. In a case study on copper and silver nanoparticles, encapsulation in graphene nanoreactors is shown in some cases to enhance their oxidation rate in aqueous media, which is attributed to electron transfer from the metal core to graphene that bypasses surface oxides and allows reduction of molecular oxygen on the high-area graphene shell. Nanoreactors also allow particle-particle electron transfer interactions that are mediated by the connecting conductive graphene, which give rise to novel behaviors such as galvanic protection of Ag nanoparticles in Ag/Ni-filled nanoreactors, and the photochemical control of Ag-ion release in Ag/TiO2-filled nanoreactors. It is also shown that internal graphene structures within the sacks provide pockets that reduce particle mobility and inhibit particle sintering during thermal treatment. Finally, these novel behaviors are used to suggest and demonstrate several potential applications for graphene nanoreactors in catalysts, controlled release, and environmental remediation.