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Photocatalytic water splitting for green hydrogen production is hindered by the sluggish kinetics of oxygen evolution reaction (OER). Loading a co-catalyst is essential for accelerating the kinetics, but the detailed reaction mechanism and role of the co-catalyst are still obscure. Here, we focus on cobalt oxide (CoOx) loaded on bismuth vanadate (BiVO4) to investigate the impact of CoOx on the OER mechanism. We employ photoelectrochemical impedance spectroscopy and simultaneous measurements of photoinduced absorption and photocurrent. The reduction of V5+ in BiVO4 promotes the formation of a surface state on CoOx that plays a crucial role in the OER. The third-order reaction rate with respect to photohole charge density indicates that reaction intermediate species accumulate in the surface state through a three-electron oxidation process prior to the rate-determining step. Increasing the excitation light intensity onto the CoOx-loaded anode improves the photoconversion efficiency significantly, suggesting that the OER reaction at dual sites in an amorphous CoOx(OH)y layer dominates over single sites. Therefore, CoOx is directly involved in the OER by providing effective reaction sites, stabilizing reaction intermediates, and improving the charge transfer rate. These insights help advance our understanding of co-catalyst-assisted OER to achieve efficient water splitting. [ABSTRACT FROM AUTHOR]

Solar-powered electrochemical production of hydrogen through water electrolysis is an active and important research endeavor. However, technologies and roadmaps for implementation of this process do not exist. In this perspective paper, we describe potential pathways for solar-hydrogen technologies into the marketplace in the form of photoelectrochemical or photovoltaic-driven electrolysis devices and systems. We detail technical approaches for device and system architectures, economic drivers, societal perceptions, political impacts, technological challenges, and research opportunities. Implementation scenarios are broken down into short-term and long-term markets, and a specific technology roadmap is defined. In the short term, the only plausible economical option will be photovoltaic-driven electrolysis systems for niche applications. In the long term, electrochemical solar-hydrogen technologies could be deployed more broadly in energy markets but will require advances in the technology, significant cost reductions, and/or policy changes. Ultimately, a transition to a society that significantly relies on solar-hydrogen technologies will benefit from continued creativity and influence from the scientific community.

A semiconductive oxide, La2CuO4 (LCO), was investigated as a potential material to compose photocathode for sunlight-driven hydrogen evolution by splitting water. LCO, despite involving partially filled Cu 3d orbitals, behaves as a semiconductor and absorbs visible light on the bandgap formed by significant Coulomb repulsion between the electronic orbitals. An epitaxial LCO film was grown on a SrRuO3/SrTiO3 (SRO/STO) single-crystal substrate by pulsed laser deposition to obtain a photocathodic specimen for water photo-splitting. An LCO photocathode dressed with a Pt cocatalyst for hydrogen evolution (Pt/LCO/SRO/STO) exhibited a cathodic photocurrent with a density of 0.4 mA cm−2 at 0 VRHE under simulated AM1.5 G sunlight. This photocathode responded to incident light up to 800 nm, which is one of the longest wavelengths so far reported for an oxide photoelectrode. Together with a counter-electrode for oxygen evolution, the Pt/LCO/SRO/STO photocathode generated hydrogen with the expected H2 : O2 = 2 : 1 stoichiometric ratio with a Faradaic efficiency of approximately 80%. [ABSTRACT FROM AUTHOR]

Among the different forms of cerebellar ataxia, autoimmune cerebellar ataxia (ACA) or immune‐mediated cerebellar ataxia (IMCA), which appears to be based on an autoimmune mechanism, has long been considered important from the viewpoint of paraneoplastic syndrome. With the expansion of the concept of immune‐mediated neurological diseases and the identification of many novel autoantibodies, ACA has recently become an important neurological syndrome. Although no definitive diagnostic criteria of ACA exist, Hadjivassilou et al suggested diagnostic criteria for primary ACA in 2020 and Dalmau and Graus showed proposed diagnostic criteria for ACA in 2022. The proposed diagnostic criteria for ACA by Dalmau and Graus emphasize the importance of antibody reliability. In the future, additional studies should be conducted to identify new antibodies associated with ACA and to clarify the importance of each antibody. Moreover, ACA is a disease for which immunological therapeutic intervention is feasible and requires early treatment to maintain cerebellar function. Many cases with ACA have reported the efficacy of immunotherapy. The concept of ACA may have the potential for further expansion and becomes increasingly important in the diagnosis of cerebellar ataxia. [ABSTRACT FROM AUTHOR]

A water-soluble Co complex with dimethyl-bipyridine ligands reduced CO2 to CO electrochemically with almost 100% selectivity at −0.80 V vs. NHE in an aqueous medium (pH 6.8) without an organic solvent. The reaction overpotential was 270 mV. A possible CO formation mechanism was discussed based on experiments and calculations. [ABSTRACT FROM AUTHOR]

Ag+ substitution was applied to a tungsten-bronze-type metal oxide. An AgSr2Ta5O15 photocatalyst has emerged for water splitting and CO2 reduction. DFT calculation and diffuse reflection spectra revealed that the Ag d-orbital formed a new valence band, leading to a narrow band gap (3.91 eV) compared to that of NaSr2Ta5O15 (4.11 eV). [ABSTRACT FROM AUTHOR]