The kinetically sluggish rate of oxygen reduction reaction (ORR) on the cathode side is one of the main bottlenecks of zinc-air batteries (ZABs), and thus the search for an efficient and cost-effective catalyst for ORR is highly pursued. Co O has received ever-growing interest as a promising ORR catalyst due to the unique advantages of low-cost, earth abundance and decent catalytic activity. However, owing to the poor conductivity as a result of its semiconducting nature, the ORR activity of the Co O catalyst is still far below the expectation. Herein, we report a controllable N-doping strategy to significantly improve the catalytic activity of Co O for ORR and demonstrate these N doped Co O nanowires as an additive-free air-cathode for flexible solid-state zinc-air batteries. The results of experiments and DFT calculations reveal that the catalytic activity is promoted by the N dopant through a combined set of factors, including enhanced electronic conductivity, increased O adsorption strength and improved reaction kinetics. Finally, the assembly of all-solid-state ZABs based on the optimized cathode exhibit a high volumetric capacity of 98.1 mAh cm and outstanding flexibility. The demonstration of such flexible ZABs provides valuable insights that point the way to the redesign of emerging portable electronics.

The development of an earth-abundant, first-row water oxidation catalyst that operates at neutral pH and low overpotential remains a fundamental chemical challenge. Herein, we report the first nickel-based robust homogeneous water oxidation catalyst, which can electrocatalyze water oxidation at neutral pH and low overpotential in phosphate buffer. The results of DFT calculations verify that the O-O bond formation in catalytic water oxidation prefers a HO-OH coupling mechanism from a cis-isomer of the catalyst.

A general mechanism for H2 activation by Lewis acid–transition metal (LA-TM) bifunctional catalysts has been presented via density functional theory (DFT) studies on a representative nickel borane system, (PhDPBPh)­Ni. There are four typical H2 activation modes for LA-TM bifunctional catalysts: (1) the cis homolytic mode, (2) the trans homolytic mode, (3) the synergetic heterolytic mode, and (4) the dissociative heterolytic mode. The feature of each activation mode has been characterized by key transition state structures and natural bond orbital analysis. Among these four typical modes, (PhDPBPh)Ni catalyst most prefers the synergetic heterolytic mode (ΔG ‡ = 29.7 kcal/mol); however the cis homolytic mode cannot be totally disregarded (ΔG ‡ = 33.7 kcal/mol). In contrast, the trans homolytic mode and dissociative heterolytic mode are less feasible (ΔG ‡ = ∼42 kcal/mol). The general mechanistic picture presented here is fundamentally important for the development and rational design of LA-TM catalysts in the future.

The hydrogenation of carbon dioxide catalyzed by half-sandwich transition metal complexes (M = Co, Rh, and Ir) was studied systematically through density functional theory calculations. All metal complexes are found to process a similar mechanism, which involves two main steps, the heterolytic cleavage of H2 and the hydride transfer. The heterolytic cleavage of H2 is the rate-determining step. The comparison of three catalytic systems suggests that the Ir catalyst has the lowest activation free energy (13.4 kcal/mol). In contrast, Rh (14.2 kcal/mol) and Co (18.3 kcal/mol) catalysts have to overcome relatively higher free energy barriers. The different catalytic efficiency of Co, Rh, and Ir is attributed to the back-donation ability of different metal centers, which significantly affects the H2 heterolytic cleavage. The highest activity of an iridium catalyst is attributed to its strong back-donation ability, which is described quantitatively by the second order perturbation theory analysis. Our study indicates that the functional group of the catalyst plays versatile roles on the catalytic cycle to facilitate the reaction. It acts as a base (deprotonated) to assist the heterolytic cleavage of H2. On the other hand, during the hydride transfer, it can also serve as Brønsted acid (protonated) to lower the LUMO of CO2. This ligand assisted pathway is more favorable than the direct attack of hydride to CO2. These finds highlight that the unique features of the metal center and the functional ligands are crucial for the catalyst design in the hydrogenation of carbon dioxide.

To determine the hepatitis C virus (HCV) genotype distribution in Taiwan and to clarify the relationship between genotype and the pathogenesis of HCV infection, 1,164 subjects positive for serum HCV antibodies and HCV RNA from three HCV hyperendemic areas (Masago, Tzukuan, and Taoyuan) and a tertiary referral center in Taiwan were studied during 1995-1997. HCV genotypes and viral loads were determined using Okamoto's method and branched DNA assay, respectively. Genotype 1b was the most prevalent in Tzukuan (61.9%), Taoyuan (76.9%), and the referral center (47.0%). By contrast, genotype 2a was the major HCV type in Masago (63.5%). Prevalence of genotype 1b positively and that of genotype 2a negatively correlated to age, regardless of study populations (P < 0.01). Based on multivariate analysis, the significant factors associated with the presence of cirrhosis, with or without hepatocellular carcinoma, in chronic hepatitis C patients were genotype 1b and age. In conclusion, these results underline that independent HCV outbreaks continue in HCV hyperendemic areas in Taiwan, concomitant with a changing relative prevalence of HCV genotypes in relation to age. Both the correlation of genotype 1b with age (cohort effect) and intrinsic properties of HCV genotypes are probably responsible for the association between genotype and the pathogenesis of HCV infection.