In Situ Electrochemical Conversion of an Ultrathin Tannin Nickel Iron Complex Film as an Efficient Oxygen Evolution Reaction Electrocatalyst

The oxygen evolution reaction (OER) is an important half reaction in many energy conversion and storage techniques. However, the development of a low‐cost easy‐prepared OER electrocatalyst with high mass activity and rapid kinetics is still challenging. Herein, we report the facile deposition of tannin‐NiFe (TANF) complex film on carbon fiber paper (CP) as a highly efficient OER electrocatalyst. TANF gives rapid OER reaction kinetics with a very small Tafel slope of 28 mV dec^?1. The mass activity of TANF reaches 9.17×10³ Ag^?1 at an overpotential of 300 mV, which is nearly 200‐times larger than that of NiFe double layered hydroxide. Furthermore, tannic acid in TANF can be electrochemically extracted under anodic potential, leaving the inorganic composite Ni_xFe_1?xO_yH_z as the OER‐active species. This work may provide a guide to probing the electrochemical transformation and investigating the reactive species of other metal–organic complexes as heterogeneous electrocatalysts.     

Non‐metal Single‐Iodine‐Atom Electrocatalysts for the Hydrogen Evolution Reaction

Common‐metal‐based single‐atom catalysts (SACs) are quite difficult to design due to the complex synthesis processes required. Herein, we report a single‐atom nickel iodide (SANi‐I) electrocatalyst with atomically dispersed non‐metal iodine atoms. The SANi‐I is prepared via a simple calcination step in a vacuum‐sealed ampoule and subsequent cyclic voltammetry activation. Aberration‐corrected high‐angle annular dark‐field scanning transmission electron microscopy and synchrotron‐based X‐ray absorption spectroscopy are applied to confirm the atomic‐level dispersion of iodine atoms and detailed structure of SANi‐I. Single iodine atoms are found to be isolated by oxygen atoms. The SANi‐I is structural stable and shows exceptional electrocatalytic activity for the hydrogen evolution reaction (HER). In situ Raman spectroscopy reveals that the hydrogen adatom (H_ads) is adsorbed by a single iodine atom, forming the I‐H_ads intermediate, which promotes the HER process.     

Anionic Dopant Delocalization through p‐Band Modulation to Endow Metal Oxides with Enhanced Visible‐Light Photoactivity

An N‐doped TiO₂ model reveals a conceptually different mechanism for activating the N dopant based on delocalized orbital hybridization through O vacancy incorporation. Synchrotron‐based X‐ray absorption spectroscopy, time‐resolved fluorescence, and DFT studies revealed that O vacancy incorporation can effectively stimulate the delocalization of N impurity states through p‐band orbital modulation, which leads to a significant enhancement in photocarrier lifetime. Consequently, this effect also results in a remarkable increase in the incident photon‐to‐electron conversion efficiency in the range of 400–550 nm compared to that of conventional N‐incorporated TiO₂ (15 % versus 1 % at 450 nm). This work reveals the fundamental necessity of orbital modulation in the band engineering of metal oxides for driving solar water splitting and beyond.