Ga-Doped and Pt-Loaded Porous TiO₂–SiO₂ for Photocatalytic Nonoxidative Coupling of Methane

Abstract

Photodriven nonoxidative coupling of CH4 (NOCM) is a potential alternative approach to clean hydrogen and hydrocarbon production. Herein, a Mott–Schottky photocatalyst for NOCM is fabricated by loading Pt nanoclusters on a Ga-doped hierarchical porous TiO2–SiO2 microarray with an anatase framework, which exhibits a CH4 conversion rate of 3.48 μmol g–1 h–1 with 90% selectivity toward C2H6. This activity is 13 times higher than those from microarrays without Pt and Ga. Moreover, a continuous H2 production (36 μmol g–1) with a high CH4 conversion rate of ∼28% can be achieved through a longtime irradiation (32 h). The influence of Ga on the chemical state of a surface oxygen vacancy (Vo) and deposited Pt is investigated through a combination of experimental analysis and first-principles density functional theory calculations. Ga substitutes for the five-coordinated Ti next to Vo, which tends to stabilize the single-electron trapped Vo and reduce the electron transfer from Vo to the adsorbed Pt, resulting in the formation of a higher amount of cationic Pt. The cationic Pt and electron-enriched metallic Pt form a cationic–anionic active pair, which is more efficient for the dissociation of C–H bonds. However, the presence of too much cationic Pt results in more C2+ product with a decrease in the CH4 conversion rate due to the reduced charge-carrier separation efficiency. This study provides deep insight into the effect of the doping/loading strategy on the photocatalytic NOCM reaction and is expected to shed substantial light on future structural design and modulation.

Localized Electrons Enhanced Ion Transport for Ultrafast Electrochemical Energy Storage

“…Such electrons can be introduced in defective materials instead of exteriorly injecting, [ 16–19 ] such as the localized excess electrons at Ti atoms near the oxygen vacancy in TiO 2 . [ 16,20,21 ] We expect that the interaction between the ions and localized electrons can be harnessed to significantly improve the ion transport in electrode materials for enhanced energy storage.…”

“…[ 26 ] We assume that the localized electrons are formed at the oxygen vacancy (V o ), where excess electrons are localized near Ti atoms. [ 21 ] Figure a shows the schematic concept of localized electrons enhanced ion transport through the use of TiO 2 with localized electrons as the anode. The rate for charging and discharging process can be improved by speeding up ion diffusion in electrode materials of energy storage electrochemical devices.…”

Cation‐Modulated HER and OER Activities of Hierarchical VOOH Hollow Architectures for High‐Efficiency and Stable Overall Water Splitting

“…The specific surface area as well as the porous structure of the as‐prepared catalysts have significant influence on catalytic activities . The Brunauer–Emmett–Teller (BET) surface area (Figure c) and pore size distribution (Figure S1, Supporting Information) of five catalysts were investigated by N 2 adsorption‐desorption isotherms.…”

“…[35] The specific surface area as well as the porous structure of the as-prepared catalysts have significant influence on catalytic activities. [36,37] The Brunauer-Emmett-Teller (BET) surface area ( Figure 1c) and pore size distribution ( Figure S1, Supporting Information) of five catalysts were investigated by N 2 adsorption-desorption isotherms. From Figure 1c, the largest BET surface areas of 178.2 m 2 g −1 is recorded from VOOH-10Fe sample compared to the other four samples: 153.7 for VOOH-0Fe, 158.1 for VOOH-1Fe, 159.0 for VOOH-3Fe, and 161.9 m 2 g −1 for VOOH-5Fe.…”

A General and Straightforward Route to Noble Metal‐Decorated Mesoporous Transition‐Metal Oxides with Enhanced Gas Sensing Performance

“…Transition‐metal oxides (TMOs, e.g., WO 3 , TiO 2 , Nb 2 O 5 , and CeO 2 ) in combination with active noble metal catalysts are essential candidates in catalysis and sensors owing to their specific chemical and electronic properties . Unlike inert silica‐based or carbon‐based supports, TMOs supports are more versatile and active.…”