Direct imaging of the bulk heterojunction (BHJ) thin film morphology in polymer-based solar cells is essential to understand device function and optimize efficiency. The morphology of the BHJ active layer consists of bicontinuous domains of the donor and acceptor materials, having characteristic length scales of several tens of nanometers, that reduces charge recombination, enhances charge separation, and enables electron and hole transport to their respective electrodes. Direct imaging of the morphology from the molecular to macroscopic level, though, is lacking. Though transmission electron tomography provides a 3D, real-space image of the morphology, quantifying the structure is not possible. Here we used high-resolution atomic force microscopy (AFM) in the tapping and nanomechanical modes to investigate the BHJ active layer morphology that, when combined with Ar(+) etching, provided unique insights with unparalleled spatial resolution. PCBM was seen to form a network that interpenetrated into the fibrillar network of the hole-conducting polymer, both being imbedded in a mixture of the two components. The free surface was found to be enriched with polymer crystals having a "face-on" orientation and the morphology at the anode interface was markedly different.

We aim to achieve resource recycling by capturing and using CO 2 generated in a chemical production and disposal process. We focused on CO 2 conversion to CO by the reverse water gas shift–chemical looping (RWGS-CL) reaction. This reaction proceeds in two steps (H 2 + MO x ⇆ H 2 O + MO x –1 ; CO 2 + MO x –1 ⇆ CO + MO x ) via a metal oxide that acts as an oxygen carrier. High CO 2 conversion can be achieved owing to a low H 2 O concentration in the second step, which causes an unwanted back reaction (H 2 + CO 2 ⇆ CO + H 2 O). However, the RWGS-CL process is difficult to control because of repeated thermochemical redox cycling, and the CO 2 and H 2 conversion extents vary depending on the metal oxide composition and experimental conditions. In this study, we developed metal oxides and simultaneously optimized experimental conditions to satisfy target CO 2 and H 2 conversion extents by using machine learning and Bayesian optimization. We used transfer learning to improve the prediction accuracy of the mathematical models by incorporating a data set and knowledge of oxygen vacancy formation energy. Furthermore, we analyzed the RWGS-CL reaction based on the prediction accuracy of each variable and the feature importance of the random forest regression model.

Mn and Li promoted Rh catalysts supported on SiO 2 with a thin TiO 2 layer were synthesized by stepwise incipient wetness impregnation approach. The thin TiO 2 layer on the surface of SiO 2 was proved to stabilize those small Rh nanoparticles and hinder their agglomeration. The reducibility of Rh on these catalysts depends on Rh particle size as well as the position of manganese oxide, and large Rh nanoparticles with MnO on Rh nanoparticles can be only reduced at an elevated temperature. Catalyst with large Rh particles exhibits a higher CO conversion and higher products selectivity towards long chain hydrocarbons and C2-oxygenates at the expense of decreasing methane formation than a similar catalyst with smaller Rh particles. This was attributed to the synergistic effect of Mn and Li promotion and molar ratio between Rh 0 and Rh δ+ sites on the surface of Rh nanoparticles. Moreover, Rh nanoparticles on MnO are proved to be more efficient in promoting hydrogenation of acetaldehyde to ethanol than its counterpart with MnO on Rh nanoparticles. Finally, in order to target high C2-oxygenates selectivity, low reaction temperature together with a low H 2 /CO ratio in the feed is recommended.

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Quinone-based organic materials have reversal multielectron redox reactions. Cations in electrolytes are withdrawn or released by reduced quinone-based materials. Lithium ions being adopted, quinone-based materials are applied as an active material for lithium secondary battery. Due to their multielectron redox reactions, organic materials have an energy density even equal to inorganic materials. Inorganic materials must keep their crystal structure during cell operation, relating to reversibility of charge-discharge capacity, and the lithium conducting path in their crystal structure limit the mobility of lithium. On the other hand, organic materials do not need to keep their crystal structure owing to redox reaction within a molecule. Their electrochemical performances are not controlled by the lithium mobility in the lithium conducting path as in the case of inorganic materials. In addition, organic materials are relatively low-cost due to no metal elements and can be easily designed to fabricate their organic structure. However, their high solubility to electrolytes gives a large capacity loss, and their insulating properties lead directly to poor electron conduction during their redox reaction. These properties limit the rate performance and utilization ratio of organic materials. In this study, several organic materials, anthraquinone (AQ), 9,10-phenanthrenequinone (PQ), 1,10-phenanthroline-5,6-dione (N2PQ), and so on, were supported as much as possible on the surface of activated carbon (Maxsorb®) with nano-sized pores as a current collector for compensating their insulating properties. The organic materials-supported activated carbon was covered by a lithium conductive polymer (polyethyleneoxide, PEO) in order to restrict a dissolution of organic materials to electrolytes. The effect of organic structures on the electrochemical performance as positive electrodes was discussed. Discharge curves of positive electrodes using AQ, PQ, and N2PQ at 0.2 C show that two clear plateaus are detected for PQ (2.7 and 2.3 V) and N2PQ (2.9 and 2.5 V), respectively, and one plateau is detected for AQ (2.1 V). When two ketone groups in PQ and N2PQ are adjacent, radical anions reduced from neutral molecules through one electron redox reaction could exist stably by coordinating a lithium ion for a bridge formation. The coexistence regions of neutral molecules-radical anions and of radical anions-divalent anions result in two plateaus in the charge-discharge test of PQ and N2PQ. Redox potentials of PQ are higher than those of AQ because 1,2-diketone compound (PQ) receives a repulsion of two dipoles from each ketone, leading to a destabilization of neutral molecules and to easily reduction at the higher potential than 1,4-diketone compound (AQ). Heterocyclic compound (N2PQ) offers higher redox potential than PQ. In the field of complex chemistry, N2PQ behaves as a ligand for chelation. A resonance form of reduced N2PQ gives a negative charge to nitrogen atoms, and lithium ions are possibly withdrawn not only at oxygen atoms but also at nitrogen atoms. This coordinating ability of nitrogen atoms stabilizes the reduced form of N2PQ more than that of non-heterocyclic compound (PQ), reflecting higher redox potentials of N2PQ. Low polarization and high redox potentials in the charge-discharge test for N2PQ gives a high energy density of about 600 mWh g-1 when an electric double layer capacitance obtained from the activated carbon was removed. This value is comparable to inorganic active materials. A charge-discharge curve for N2PQ at 1.0 C shows two plateaus at 2.8 and 2.4 V. Discharge capacity in the 5th cycle at 0.2 and 1.0 C was 226 and 194 mAh g-1, respectively, and their utilization ratios of N2PQ (theoretical discharge capacity: 255 mAh g-1) were 89 and 76 %. The redox reaction of N2PQ through stable radical anion occurs smoothly to offer highly discharge capacity and rate performance.