Carbon dioxide reduction is an essential component of many prospective technologies for the renewable synthesis of carbon-containing fuels. Known catalysts for this reaction generally suffer from low energetic efficiency, poor product selectivity, and rapid deactivation. We show that the reduction of thick Au oxide films results in the formation of Au nanoparticles ("oxide-derived Au") that exhibit highly selective CO(2) reduction to CO in water at overpotentials as low as 140 mV and retain their activity for at least 8 h. Under identical conditions, polycrystalline Au electrodes and several other nanostructured Au electrodes prepared via alternative methods require at least 200 mV of additional overpotential to attain comparable CO(2) reduction activity and rapidly lose their activity. Electrokinetic studies indicate that the improved catalysis is linked to dramatically increased stabilization of the CO(2)(•-) intermediate on the surfaces of the oxide-derived Au electrodes.

The importance of tin oxide (SnO(x)) to the efficiency of CO(2) reduction on Sn was evaluated by comparing the activity of Sn electrodes that had been subjected to different pre-electrolysis treatments. In aqueous NaHCO(3) solution saturated with CO(2), a Sn electrode with a native SnO(x) layer exhibited potential-dependent CO(2) reduction activity consistent with previously reported activity. In contrast, an electrode etched to expose fresh Sn(0) surface exhibited higher overall current densities but almost exclusive H(2) evolution over the entire 0.5 V range of potentials examined. Subsequently, a thin-film catalyst was prepared by simultaneous electrodeposition of Sn(0) and SnO(x) on a Ti electrode. This catalyst exhibited up to 8-fold higher partial current density and 4-fold higher faradaic efficiency for CO(2) reduction than a Sn electrode with a native SnO(x) layer. Our results implicate the participation of SnO(x) in the CO(2) reduction pathway on Sn electrodes and suggest that metal/metal oxide composite materials are promising catalysts for sustainable fuel synthesis.

A family of three-dimensional chiral metal-formate frameworks of [NH(4)][M(HCOO)(3)] (M = Mn, Fe, Co, Ni, and Zn) displays paraelectric to ferroelectric phase transitions between 191 and 254 K, triggered by disorder-order transitions of NH(4)(+) cations and their displacement within the framework channels, combined with spin-canted antiferromagnetic ordering within 8-30 K for the magnetic members, providing a new class of metal-organic frameworks showing the coexistence of magnetic and electric orderings.

We present here a structural and mechanistic description of how a protein changes its fold and function, mutation by mutation. Our approach was to create 2 proteins that (i) are stably folded into 2 different folds, (ii) have 2 different functions, and (iii) are very similar in sequence. In this simplified sequence space we explore the mutational path from one fold to another. We show that an IgG-binding, 4␤؉␣ fold can be transformed into an albumin-binding, 3-␣ fold via a mutational pathway in which neither function nor native structure is completely lost. The stabilities of all mutants along the pathway are evaluated, key high-resolution structures are determined by NMR, and an explanation of the switching mechanism is provided. We show that the conformational switch from 4␤؉␣ to 3-␣ structure can occur via a single amino acid substitution. On one side of the switch point, the 4␤؉␣ fold is >90% populated (pH 7.2, 20°C). A single mutation switches the conformation to the 3-␣ fold, which is >90% populated (pH 7.2, 20°C). We further show that a bifunctional protein exists at the switch point with affinity for both IgG and albumin.evolution ͉ NMR ͉ protein design ͉ protein folding