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Abstract:The use of hematite as the photoanode for photoelectrochemical hydrogen production by solar energy has been actively studied due to its abundance, stability, and adequate optical properties. Deposition of an electrocatalyst overlayer on the hematite may increase kinetics and lower the onset potential for water splitting. Ni x Fe 1−x O y is one of the most effective electrocatalysts reported for this purpose. However, the condition and results of the previous reports vary significantly, and a comprehensive model for Ni x Fe 1−x O y /hematite is lacking. Here, we report a simple and novel chemical bath deposition method for depositing low-onset-potential Ni x Fe 1−x O y electrocatalyst on hematite. With a Ni percentage of 80% and an immersion time of 2 min, the as-prepared Ni x Fe 1−x O y overlayer raised the photovoltage from 0.2 V to 0.7 V, leading to a cathodic shift of the onset potential by 400 mV, while maintaining the same level of current density. The dependence of the electrochemical and photoelectrochemical characteristics of the photoanode on the condition of the electrocatalyst was studied systematically and explained based on energy level diagrams and kinetics.

The practical application of Li0.5+xLa0.5TiO3(LLTO) perovskite structural materials is limited by its low total conductivity. In order to improve the ionic conductivity, different ratios of Li-doping material were investigated in this study. LLTO materials were synthesized by the solid-state reaction method. From XRD pattern results, with increasing the ratio of Li/La to 1.6, the structure of the Li0.8La0.5TiO3 material was starting to change from complete perovskite structure to partial Ruddlesden–Popper perovskite structure. Also, the ohmic resistance of the LLTO materials decreased with the ratios of Li/La from 1 to 1.5. As the ratios of Li/La were larger than 1.6, the ohmic resistance would increase because of the structure change.