High-performance photocatalytic nonoxidative conversion of methane to ethane and hydrogen by heteroatoms-engineered TiO2

Abstract

Nonoxidative coupling of methane (NOCM) is a highly important process to simultaneously produce multicarbons and hydrogen. Although oxide-based photocatalysis opens opportunities for NOCM at mild condition, it suffers from unsatisfying selectivity and durability, due to overoxidation of CH4 with lattice oxygen. Here, we propose a heteroatom engineering strategy for highly active, selective and durable photocatalytic NOCM. Demonstrated by commonly used TiO2 photocatalyst, construction of Pd–O4 in surface reduces contribution of O sites to valence band, overcoming the limitations. In contrast to state of the art, 94.3% selectivity is achieved for C2H6 production at 0.91 mmol g–1 h–1 along with stoichiometric H2 production, approaching the level of thermocatalysis at relatively mild condition. As a benchmark, apparent quantum efficiency reaches 3.05% at 350 nm. Further elemental doping can elevate durability over 24 h by stabilizing lattice oxygen. This work provides new insights for high-performance photocatalytic NOCM by atomic engineering.

Oxygen Vacancies Enhanced Ozonation toward Phenol Derivatives Removal over Ov-Bi2O3

“…XPS spectra were further carried out to verify the presence of oxygen vacancies in O v -Bi 2 O 3 . As shown in Figure a, compared with Bi 2 O 3 , the intensity for adsorbed oxygen (at 531.4 eV) for O v -Bi 2 O 3 significantly enhances, consistent with the beneficial effect of oxygen vacancies on oxygen adsorption. − In addition, the Bi 4f spectra show that, compared with Bi 2 O 3 (at 159.0 and 164.3 eV), the Bi 4f 7/2 and 4f 5/2 of O v -Bi 2 O 3 (at 158.9 and 164.2 eV) shift toward a lower binding energy, which means that the introduction of oxygen vacancies increases the electron density of Bi (Figure b) . What is more, UV–vis DRS spectra show that, compared with Bi 2 O 3 , O v -Bi 2 O 3 displays an absorption band nearly covering the full spectra, which can be ascribed to the presence of oxygen vacancies (Figure c) .…”

Direct Photocatalytic Synthesis of Acetic Acid from Methane and CO at Ambient Temperature Using Water as Oxidant

“…This AQY is comparable to the most advanced photocatalytic methane transformation systems in nonoxidative coupling (Table S1). ,,,− Note that this AQY in this work was achieved using water as a soft oxidizing agent and without the use of toxic or aggressive oxidants such as H 2 O 2 or O 2 .…”

Beyond reduction cocatalysts: critical role of metal cocatalysts in photocatalytic oxidation of methane with water

“…have generally been recognized as reduction cocatalysts that capture photogenerated electrons and promote reduction reactions such as H2 evolution, while oxidation reactions are generally believed to be accelerated by non-metallic cocatalysts such as metal oxides (CoOx, CuOx, PdOx, etc.) [14][15][16][17][18] as reported in various spectroscopic and theoretical studies [39][40][41][42][43] . Although the possibility of hole accumulation in the metallic cocatalyst was discussed in the previous DFT calculation 44 and surface molecular spectroscopy 45 , these studies assumed that the hole-accumulated metal cocatalyst acts as just a recombination center of the photogenerated charges (e − and h + ) and cannot promote well the photocatalytic reactions 44,45 .…”