RESUMEN
Even the most stable Ir-based oxides inevitably encounter a severe degradation problem during the oxygen evolution reaction (OER) in acid, resulting in quick formation of amorphous IrOx layers on the catalyst surface. Unfortunately, there is still a lack of fundamental understanding of such hydrous IrOx layers, including the atomic arrangement, key active structure, compositions, chemical stability, and so on. In this work, we demonstrate an electrochemical strategy to prepare two types of protonated iridium oxides with well-defined crystalline structures: one possesses a 2D layered structure (denoted as α-HxIrO3) and the other consists of 3D interconnected polymorphs (denoted as ß-HxIrO3). Both protonated iridium oxides demonstrate superior electrochemical stabilities with 6 times suppressed Ir dissolution comparing to the initial Li2IrO3 and rutile IrO2. It is hypothesized that the enriched protons and fast diffusions in these two protonated HxIrO3 crystal oxides may promote surface structural stability by suppressing the formation of high-valence Ir species at the solid-liquid interfaces during OER. Overall, the results of this work shed light on the role of proton dynamics toward the OER processes on the catalyst surface in acid media.
RESUMEN
Solar-driven water splitting has been regarded as a promising strategy for renewable hydrogen production. Among many semiconductor photocatalysts, graphitic carbon nitride (g-C3N4) has received tremendous attention due to its two-dimensional structure, appropriate band gap and decent photocatalytic activity. However, it suffers severe charge recombination problems, affecting its practical performance. In this work, we demonstrated that dual heteroatoms (C and O) doped g-C3N4 can exhibit about 3 times higher catalytic performance for hydrogen evolution than that of the normal g-C3N4 with a hydrogen evolution rate reaching 2595.4 umol g-1h-1 and an apparent quantum efficiency at 420 nm of 16.6%. The heteroatoms (C and O) doped g-C3N4 photocatalyst also exhibited superior removal performance when removing Rhodamine B (RhB) . X-ray photoelectron spectroscopy (XPS), solid-state nuclear magnetic resonance (ssNMR) and X-ray absorption near-edge structure (XANES) spectroscopy reveal that the carbon and oxygen dopants replace the sp2 nitrogen and bridging N atom, respectively. DFT calculations demonstrate the codoping of carbon and oxygen- induced the generation of mid-gap state, leading to the improvement of light harvesting and charge separation.