Harnessing energy for a sustainable world.

Innovation through scientific discovery is a necessary component of much societal advancement. To truly implement sustainable practices, energy must be harnessed more cleanly and stored for efficient distribution and use. This systems-level change, sometimes referred to as the New Industrial Revolution, will require novel materials as well as savvy analysis and modeling to ensure success. We have thus chosen a theme of “Harnessing Energy for a Sustainable World” for this issue of JACS Select, which for the first time draws content from two ACS journals: Journal of the American Chemical Society (JACS) and EnVironmental Science & Technology (ES&T). The theme was timed in concert with the 2010 ACS Spring National Meeting’s similar focus on “Chemistry for a Sustainable World”. The publications selected from JACS concern materials and methods for energy production and storage; those from ES&T speak to how energy could (viz. should) be cleverly harnessed. The 11 JACS articles and communications in this collection consider structural aspects of energy conversion and storage. The hydrogen fuel cell in automobiles is a promising technology for reduction of carbon emissions that result from burning fossil fuels, but its development requires the discovery of more active and less expensive electrocatalysts for the oxygen reduction reaction (ORR) at the fuel cell cathode. Catalytic platinum particles have been the technological mainstay of the field for decades, but scientific breakthroughs in relating catalyst structure to ORR activity, as well as the development of less-expensive non-noble-metal catalysts, are rapidly appearing. Wang and Adzic reported enhancement of the ORR by depositing monolayer Pt films on Pd3Co nanoparticles, a consequence of the influence of compressive strains in the Pt shell on the oxygen binding energy. The reverse of the ORR, i.e., the splitting of water, is a viable means to store chemical energy using solar-generated electricity, but this process also requires new and inexpensive catalysts. Two very different approaches to water oxidation catalysts reported in JACS show particular promise: Nocera developed an inexpensive and self-healing oxygen-evolving catalyst based on the electrodeposition of thin films of Co2+ salts, while Murray used freely diffusing 1.6 nm catalytic IrO2 nanoparticles in aqueous solution as the redox mediator to oxidize water to O2. 3 Both chemistries exhibit 100% Faradaic efficiencies at relatively low electrical driving force. While lithium-ion batteries remain the leading technology for powering electronics and electric vehicles, recent advances in materials chemistry are providing opportunities for more environmentally friendly and efficient electrical energy storage devices. For example, using the tetralithium salt of tetrahydroxybenzoquinone, Poizot demonstrated a Li-ion battery that cycles between Li2C6O6 and Li6C6O6. 4 These sustainable “organic” electrodes may replace cobaltand iron-based battery electrodes in the future. In addition to the new electrode materials, advanced membranes for batteries and fuel cells are required, and many have been reported. A room-temperature fast-ion conductor was discovered by Maekawa by mixing lithium halides with LiBH4, yielding a new electrolyte candidate for all-solid-state room-temperature batteries. 5