Nature-inspired molecules present a family of affordable, environmentally friendly catalysts to enable and enhance next-generation energy storage systems. In this study, we report the use of cobalt-based polyoxometalates (Co-POMs) with an oxo-bridged tetracobalt active site, which is reminiscent of the natural oxygen-evolving complex, as an efficient and stable redox catalyst for Li-O 2 batteries. Interestingly, Co-POMs exhibit catalytic activity for both oxygen evolution and reduction reactions (OER and ORR, respectively) under a certain condition when it forms a stable dispersion of molecular aggregates, which can be controlled by the types of electrolyte solvents and exposure to light. As a result of the optimized OER/ORR bifunctional activity, Li-O 2 cells facilitated by Co-POM redox reactions successfully achieve improved efficiency and a longer cycle life in comparison to reference cells. The reversibility of the Li-O 2 reactions in the presence of the bifunctional Co-POM catalysts is confirmed by ex situ characterizations.

Electrochemical Li-CO 2 cells, which provide a sustainable and environmentally friendly pathway away from greenhouse gases, often suffer from sluggish kinetics for the growth and evolution of the cathode species on an electrode. The problematic irreversibility of the solid-to-gas conversion reactions can be addressed by the introduction of efficient catalysts into the Li-CO 2 cell. Here, we report the direct utilization of hemoglobin proteins, which are plentiful bioresources extracted from blood wastes, to effectively boost two-way Li-CO 2 reactions. The hemoglobin was immobilized on a cathodic electrode and showed excellent catalytic activity and improved capacity for CO 2 reduction and evolution reactions with a desirable weight ratio between the conductive carbons and the hemoglobin catalysts. We also verified the structural characteristics of lithium carbonate product species and the reversibility of the Li-CO 2 reaction by ex situ studies. The iron ion active site in a heterocyclic porphyrin ring of hemoglobin can participate in the Li-CO 2 reaction as a redox component.

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Quantum dot (QD) light-emitting diode (QLED) displays are highly promising optoelectronic devices, but several critical issues remain to be solved. The hole-electron charge balance is particularly important but hole-injection is more difficult than electron-injection in QLEDs; as a result, good hole injection ability is required. Here, we introduce a graphene oxide (GO) layer between the anode electrode and a typical hole injection layer of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) to improve the hole injection ability of a QLED device. The device with the GO/PEDOT:PSS bilayer hole injection layer exhibits a three-fold increase in brightness and external quantum efficiency as well as doubled current efficiency compared to a counterpart device using a single PEDOT:PSS layer. In addition, the turn-on voltage is improved from 8.35 V to 5.35 V. The dramatic improvements in the optoelectronic performance are attributed to the stepwise energy band structure in the hole injection bilayers; the work function of the GO layer is measured to be 4.98 eV, which reduces the interfacial barrier energy between the anode and PEDOT:PSS layer.