Sonication strategy for anchoring single metal atom oxides (W, Cu, Co) on CeO2-rGO for boosting electrocatalytic oxygen evolution reaction.

In the field of electrocatalysis, single-atomic-layer tungsten, copper, and cobalt oxide on CeO2, ethylene diamine (ED) and reduced graphene oxide (rGO) supported materials shows tremendous potential. Despite the enormous interest in single metal atom oxide (SMAO) catalysts, it is still very difficult to directly convert readily available bulk metal oxide into single atom oxide. It is crucial and tough to create high performance materials for the oxygen evolution reaction (OER) in an alkaline environment. Herein, a single tungsten, copper and cobalt atom oxide (SMAO) anchored on the CeO2 atomic layer and overall components deposited on the rGO (rGO-ED-CeO2-WCuCo) is prepared through a one-pot sonication technique. The presence of SMAO is identified by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging. The electrocatalytic performance of final rGO-ED-CeO2-WCuCo-30 nanocomposite for the OER in 1 M KOH electrolyte is evidenced by providing low overpotential of 283 mV at 10 mA cm-2. The Tafel slope for OER using rGO-ED-CeO2-WCuCo-30 electrocatalysts is 57.03 mV dec-1. The electrocatalytic activity of rGO-ED-CeO2-WCuCo-30 nanocomposites for OER was noticeably increased when compared to bare CeO2 nanorods (401 mV), rGO-ED-CeO2-WCo-30 (345 mV), rGO-ED-CeO2-WCu-30 (340 mV) and rGO-ED-CeO2-WCuCo-20 (321 mV) samples.

ZnSe and CdS Co-Sensitized TiO2 Nanorod Arrays as Photoanodes for Bias-Free Solar Hydrogen Evolution.

The efficient charge separation and surface state reactions are significant in enhancing the efficiency of photoelectrochemical hydrogen evolution. Herein, we report a ternary heterostructure consisting of CdS/ZnSe sensitized TiO2 nanorod as a photoanode. The heterojunction photoanode considerably widens the photon absorption spectral range and thereby enhances the photocurrent density up to 2 mA/cm2 at 1.23 V versus RHE which is 10 times higher than pristine TiO2 photoanode. The photoelectrochemical results demonstrate a high photocurrent density of 2 mA/cm2 with a photon-to-current conversion efficiency of 1.5 % at a very low applied bias (0.2 V vs RHE). The improved PEC performances of the multidimensional hybrid photoanode could be ascribed to the efficient visible-light absorption of ZnSe and CdS nanocrystals decorated on the surface of 1D TiO2 . The rapid electron-transfer properties owing to higher carrier density, low carrier transport resistance, and an extended lifetime of photoexcited carriers in the multidimensional ZnSe/CdS/TiO2 heterostructure with suppressed surface charge recombination are responsible for enhanced hydrogen evolution activities.