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Despite the fruitful achievements in the development of hydrogen production catalysts with record-breaking performances, there is still a lack of durable catalysts that could work under large current densities (>1000 mA cm−2). Here, we investigated the catalytic behaviors of Sr2RuO4 bulk single crystals. This crystal has demonstrated remarkable activities under the current density of 1000 mA cm−2, which require overpotentials of 182 and 278 mV in 0.5 M H2SO4 and 1 M KOH electrolytes, respectively. These materials are stable for 56 days of continuous testing at a high current density of above 1000 mA cm−2 and then under operating temperatures of 70 °C. The in-situ formation of ferromagnetic Ru clusters at the crystal surface is observed, endowing the single-crystal catalyst with low charge transfer resistance and high wettability for rapid gas bubble removal. These experiments exemplify the potential of designing HER catalysts that work under industrial-scale current density.

Funding: F.J., A.P.M., and C.W.H. acknowledge the financial support of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - TRR 288 - 422213477 (project A10). H.S.R. and S.H.S. acknowledge the financial support of the Engineering and Physical Sciences Research Council (UK). H.S.R. acknowledges support from the Aker Scholarship. T.S. acknowledges the support of the Natural Sciences and Engineering Research Council of Canada (NSERC), in particular the Discovery Grant [RGPIN-2020-05842], the Accelerator Supplement [RGPAS-2020-00060], and the Discovery Launch Supplement [DGECR-2020-00222]. N.K. is supported by a KAKENHI Grants-in-Aids for Scientific Research (Grant Nos.17H06136, 18K04715, and 21H01033), and Core-to-Core Program (No. JPJSCCA20170002) from the Japan Society for the Promotion of Science (JSPS) and by a JST-Mirai Program (Grant No. JPMJMI18A3). Applying in-plane uniaxial pressure to strongly correlated low-dimensional systems has been shown to tune the electronic structure dramatically. For example, the unconventional superconductor Sr2RuO4 can be tuned through a single Van Hove point, resulting in strong enhancement of both Tc and Hc2. Out-of-plane (c axis) uniaxial pressure is expected to tune the quasi-two-dimensional structure even more strongly, by pushing it towards two Van Hove points simultaneously. Here, we achieve a record uniaxial stress of 3.2 GPa along the c axis of Sr2RuO4. Hc2 increases, as expected for increasing density of states, but unexpectedly Tc falls. As a first attempt to explain this result, we present three-dimensional calculations in the weak interaction limit. We find that within the weak-coupling framework there is no single order parameter that can account for the contrasting effects of in-plane versus c-axis uniaxial stress, which makes this new result a strong constraint on theories of the superconductivity of Sr2RuO4. Publisher PDF

We report dye-degradation effects of a semiconductor LiBiO3 revealed under illumination of a conventionally used white fluorescent light. Optical absorbance spectra of LiBiO3 were broadened so smoothly, with the absorption edge penetrated to around 730 nm, that the material was able to absorb a wide range of visible light. Results showed that solution of a standard dye, methylene blue, was degraded completely after 4 h illumination. Furthermore, the value of total organic carbon decreased 70% in the decolorized solution, suggesting that the molecular form of the original methylene blue was mineralized effectively to nonorganic fragments by the photoinduced oxidization effect. Moreover, the wavelength dependence of apparent photonic efficiency was evaluated using a standard Xe lamp coupled with monochromatic filters. These results were interpreted from the viewpoint of this material’s electronic structure.

A break in periodicity occurs in the actinide series between plutonium and americium as the result of the localization of 5f electrons. The subsequent chemistry of later actinides is thought to closely parallel lanthanides in that bonding is expected to be ionic and complexation should not substantially alter the electronic structure of the metal ions. Here we demonstrate that ligation of californium(III) by a pyridine derivative results in significant deviations in the properties of the resultant complex with respect to that predicted for the free ion. We expand on this by characterizing the americium and curium analogues for comparison, and show that these pronounced effects result from a second transition in periodicity in the actinide series that occurs, in part, because of the stabilization of the divalent oxidation state. The metastability of californium(II) is responsible for many of the unusual properties of californium including the green photoluminescence., The chemistry of the post-plutonium actinides is thought to resemble lanthanides in that bonding is primarily ionic. Here, the authors show that a californium(III) complex displays significantly different properties to those predicted for the free ion owing to a second break in actinide periodicity.