The electrochemical reduction of carbon monoxide is a promising approach for the renewable production of carbon-based fuels and chemicals. Copper shows activity toward multi-carbon products from CO reduction, with reaction selectivity favoring two-carbon products; however, efficient conversion of CO to higher carbon products such as n-propanol, a liquid fuel, has yet to be achieved. We hypothesize that copper adparticles, possessing a high density of under-coordinated atoms, could serve as preferential sites for n-propanol formation. Density functional theory calculations suggest that copper adparticles increase CO binding energy and stabilize two-carbon intermediates, facilitating coupling between adsorbed *CO and two-carbon intermediates to form three-carbon products. We form adparticle-covered catalysts in-situ by mediating catalyst growth with strong CO chemisorption. The new catalysts exhibit an n-propanol Faradaic efficiency of 23% from CO reduction at an n-propanol partial current density of 11 mA cm−2.

As the lightest and cheapest transition metal dichalcogenide, TiS possesses great potential as an electrode material for lithium batteries due to the advantages of high energy density storage capability, fast ion diffusion rate, and low volume expansion. Despite the extensive investigation of its electrochemical properties, the fundamental discharge-charge reaction mechanism of the TiS electrode is still elusive. Here, by a combination of ex situ and operando X-ray absorption spectroscopy with density functional theory calculations, we have clearly elucidated the evolution of the structural and chemical properties of TiS during the discharge-charge processes. The lithium intercalation reaction is highly reversible and both Ti and sulfur are involved in the redox reaction during the discharge and charge processes. In contrast, the conversion reaction of TiS is partially reversible in the first cycle. However, Ti-O related compounds are developed during electrochemical cycling over extended cycles, which results in the decrease of the conversion reaction reversibility and the rapid capacity fading. In addition, the solid electrolyte interphase formed on the electrode surface is found to be highly dynamic in the initial cycles and then gradually becomes more stable upon further cycling. Such understanding is important for the future design and optimization of TiS based electrodes for lithium batteries.

Efforts have been made to elucidate the origin of d(0) magnetism in ZnO nanocactuses (NCs) and nanowires (NWs) using X-ray-based microscopic and spectroscopic techniques. The photoluminescence and O K-edge and Zn L3,2-edge X-ray-excited optical luminescence spectra showed that ZnO NCs contain more defects than NWs do and that in ZnO NCs, more defects are present at the O sites than at the Zn sites. Specifically, the results of O K-edge scanning transmission X-ray microscopy (STXM) and the corresponding X-ray-absorption near-edge structure (XANES) spectroscopy demonstrated that the impurity (non-stoichiometric) region in ZnO NCs contains a greater defect population than the thick region. The intensity of O K-edge STXM-XANES in the impurity region is more predominant in ZnO NCs than in NWs. The increase in the unoccupied (occupied) density of states at/above (at/below) the conduction-band minimum (valence-band maximum) or the Fermi level is related to the population of defects at the O sites, as revealed by comparing the ZnO NCs to the NWs. The results of O K-edge and Zn L3,2-edge X-ray magnetic circular dichroism demonstrated that the origin of magnetization is attributable to the O 2p orbitals rather than the Zn d orbitals. Further, the local density approximation (LDA) + U verified that vacancies in the form of dangling or unpaired 2p states (due to Zn vacancies) induced a significant local spin moment in the nearest-neighboring O atoms to the defect center, which was determined from the uneven local spin density by analyzing the partial density of states of O 2p in ZnO.

Proton exchange membrane fuel cells (PEMFCs) offer an attractive zero-emission mobile power source. However, the requirement of excessive platinum group metal (PGM) catalysts to facilitate the sluggish oxygen reduction reaction (ORR) in PEMFCs has prevented their widespread adoption. Despite tremendous progress in catalyst development with greatly increased catalytic activities, the reduction of PGM loading in practical PEMFCs remains a challenge. The ORR in PEMFCs occurs at a catalyst-electrolyte-gas three-phase interface, with multi-faceted challenges involving the activity of the catalysts, available active sites, and concerted transport of the reactants (oxygen, protons) to and removal of the product (water) from the active sites. The reduction of PGM loading reduces the number of catalytic sites, requiring a higher reaction rate on each site to sustain the overall power output, which in turn necessitates faster delivery of the reactants to and removal of the products from each active site. A desirable interface must allow efficiently feeding oxygen and protons to the catalytic sites without starving the reaction and must allow timely removal of water to avoid interface flooding. Herein we report the design of the three-phase microenvironment in PEFMCs by tailoring the interactions between the carbon supports and the electrolyte ionomers. We show that the carbon surface with 2.4% oxygen interacts with the ionomers through both its hydrophilic and hydrophobic regions, creating favorable transport paths for rapid delivery of both oxygen and protons, and timely removal of water. Such an elaborated interfacial design allows reducing costly platinum catalysts while maintaining state-of-the-art performance. For the first time we demonstrate PEMFCs with all key ORR catalyst performance metrics, including mass activity, rated power and durability, surpassing the U.S. DOE targets.