Cobalt hexacyanoferrate as an effective cocatalyst boosting water oxidation on oxynitride TaON photocatalyst under visible light

Enhanced catalytic activity of solubilised species obtained by counter-cation exchange of K{CoII 1.5[FeII(CN)6]} for water oxidation

A cyano-bridged coordination polymer, K{CoII 1.5[FeII(CN)6]} {(K)Co-Fe}, reported as a highly active heterogeneous catalyst for water oxidation was solubilised by a conventional counter-cation exchange of K+ with Me4N+ ions to provide the homogeneous catalyst of (Me4N){CoII 1.5[FeII(CN)6]} {(Me4N)Co-Fe}. (Me4N)Co-Fe exhibited enhanced catalytic activity for photocatalytic water oxidation using [Ru(2,2'-bipyridine)3]2+ and S2O8 2- as a photosensitiser and a sacrificial electron acceptor, respectively, in terms of the initial reaction rate (1.26 μmol min-1), which is about twice that of (K)Co-Fe (0.61 μmol min-1). Powder X-ray diffraction, pair distribution function and electrospray ionization mass spectrometry measurements of (Me4N)Co-Fe manifested that small heptanuclear clusters of {Co4[Fe(CN)6]3}4- formed by depolymerisation are catalytically active species in solution.

Aurivillius-layered Bi2WO6 nanoplates with CoOx cocatalyst as high-performance piezocatalyst for hydrogen evolution

Developing a high-performance piezocatalyst that directly transforms mechanical energy into hydrogen is highly desirable in the field of new energy. Herein, the Aurivillius-layered Bi2WO6 (BWO) nanoplates are prepared through a hydrothermal reaction at a moderate temperature of 160 °C, and exhibit strong piezoelectric properties, enabling them to catalyze water splitting through ultrasonic-induced piezocatalysis effect. The hydrogen evolution reaction (HER) and H2O2 generation efficiencies are measured to be 0.43 and 0.36 mmol g-1 h-1, respectively. To further boost piezocatalytic performance, cobalt oxide nanoparticles are intentionally photo-deposited onto these nanoplates as cocatalyst. This configuration results in a significantly boosted HER performance with an efficiency of 3.59 mmol g-1 h-1, which is 2.8 times higher than that of pristine nanoplates and demonstrates strong competitiveness compared to other reported piezocatalysts. The cobalt oxide cocatalyst plays a crucial role in facilitating efficient charge separation and migration, increasing the charge concentration, and ultimately enhancing piezocatalytic HER activity. Overall, this work highlights the potential of Aurivillius-layered bismuth oxide compounds as efficient piezocatalysts and provides valuable insights for designing high-performance piezocatalysts in the field of new energy.