Abstract In order to achieve highly‐efficient water electrolysis, an effective strategy is to design three‐dimensional hierarchical nanostructures by decorating the surface of the main catalysts with co‐catalytic metal compounds. Herein, leave‐like ultrathin Co(OH) 2 nanoflakes are grown on branch‐like Cu(OH) 2 nanowires via the combination of an anodization process together with an electrodeposition process. The resulting hierarchical Cu(OH) 2 @Co(OH) 2 nanotrees can be used as efficient OER electrocatalysts with an overpotential as low as 283 mV to reach 10 mA cm −2 . After 20 hours of multi‐current density stability test, the electrode shows negligible degradation while retaining an overpotential of 290 mV to reach 10 mA cm −2 , thus showing a high electrocatalytic capability and stability. This work provides a new strategy to improve transition metal electrocatalysts in view of low‐cost water oxidation in alkaline media.
Abstract We report on the use of 2,2′,6,6′‐tetraphenyldipyranylidene (DIPO‐Ph 4 ), a large quinoidal planar π‐conjugated heterocycle, as a simple, easy‐to‐synthetize, and efficient dopant‐free hole‐transport material in perovskite solar cells (PSCs). PSCs using pristine DIPO‐Ph 4 show photon conversion efficiencies up to 10.1 %, which is higher than a PSC utilizing dopant‐free spiro‐OMeTAD (5.1 %). DIPO‐Ph 4 ‐based PSCs exhibit a short‐circuit current density of 19.52 mA cm −2 and an open‐circuit voltage of 0.933 V, values that are superior to dopant‐free spiro‐OMeTAD and comparable to doped spiro‐OMeTAD. These better performances find their origin in a higher HOMO level (−4.74 eV) and a much higher hole mobility (2×10 −2 cm 2 V −1 s −1 ). Finally, PSCs based on DIPO‐Ph 4 possess a superior stability compared to doped‐spiro‐OMeTAD‐based devices when tested over 600 h.
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