Photogenerated hole traps in metal-organic-framework photocatalysts for visible-light-driven hydrogen evolution

Abstract

Efficient electron-hole separation and carrier utilization are key factors in photocatalytic systems. Here, we use a metal-organic framework (NH2-UiO-66) modified with inner platinum nanoparticles and outer cadmium sulfide (CdS) nanoparticles to construct the ternary composite Pt@NH2-UiO-66/CdS, which has a spatially separated, hierarchical structure for enhanced visible-light-driven hydrogen evolution. Relative to pure NH2-UiO-66, Pt@NH2-UiO-66, and NH2-UiO-66/CdS samples, the Pt@NH2-UiO-66/CdS composite exhibits much higher hydrogen yields with an apparent quantum efficiency of 40.3% at 400 nm irradiation and stability over the most MOF-based photocatalysts. Transient absorption measurements reveal spatial charge-separation dynamics in the composites. The catalyst’s high activity and durability are attributed to charge separation following an efficient photogenerated hole-transfer band-trap pathway. This work holds promise for enhanced MOF-based photocatalysis using efficient hole-transfer routes.

Indanone-based conjugated polymers enabling ultrafast electron transfer for visible light-driven hydrogen evolution from water

“…Importantly, ICTDB, with its relatively larger s 1 lifetime component, demonstrates the fastest electron transfer ability, along with the least impact of charge recombination among the three photocatalysts. 11,[65][66][67]69,70,73,74 These ndings are consistent with the HER performance of these polymers and underscore the superior charge transfer capability of ICTDB as a photocatalyst.…”

“…In all cases, a positive signal emerged beyond 700 nm, indicating the presence of photoinduced absorption (PIA) associated with the absorption of singlet excitons. [64][65][66] To elucidate the origins of the PIA signal, we conducted kinetic decay and tting analyses on the curves displaying the highest PIA signals, as detailed in Fig. S35 † and Table 2.…”

Chemical Vapor Deposition of Er-Doped WS2 Flakes with Near-Infrared Emission and Enhanced Near-Infrared Photoresponse

“…Meanwhile, compared with the WS 2 -based device, the WE-based device shows a ∼14-times increase in I light and ∼16.9-times increase in I ph , indicating a great enhancement in the NIR photoresponse of monolayer WE. The photoresponse of pure WS 2 under 808 nm laser excitation can be attributed to the generation of nonequilibrium carriers induced by the defect-related traps. , The increased I ph of the WE-based device can be attributed to the selective trapping of Er 3+ ions for 808 nm photons, and the promoting effect of impurity ion energy levels (around the Fermi level) on the separation of electron–hole pairs . Er 3+ ions can absorb 808 nm photons, and then transfer energy to the host, resulting in photogenerated electron–hole pairs .…”

Impact of the Crystallinity of Covalent Organic Frameworks on Photocatalytic Hydrogen Evolution

“…Recently, crystalline semiconductors with uniform and ordered pore structures such as zeolites, , MOFs, − and COFs , have been widely investigated as heterogeneous photocatalysts for hydrogen generation. However, the MOF framework is composed entirely of coordination bonds (∼50–200 kJ mol –1 ), which have a lower binding energy than covalent bonds (∼200–900 kJ mol –1 ) .…”