Photocatalytic hydrogen evolution by two comparable [FeFe]‐hydrogenase mimics assembled to the surface of ZnS

Abstract

Two photocatalytic hydrogen evolution systems were constructed by assembling [FeFe]-hydrogenase mimics, either carboxyl group-containing (C1) or not (C2), on to the surface of ZnS using triethanolamine as electron donor in DMF-H 2 O (9/1, v/v) solution. Upon irradiation for 30 h, the turnover numbers of hydrogen evolution were 3400 and 4950 for the hybrid system C1/ZnS and C2/ZnS, respectively. The photocatalytic activity of the C2/ZnS system was five times higher than the activity of the pristine ZnS, suggesting that the [FeFe]-hydrogenase mimics are crucial toward improving the activity of ZnS. On the basis of the spectroscopic studies and analyses, the photogenerated electron transfer from ZnS to the mimics is probably responsible for the activity enhancement of ZnS. The time dependence of hydrogen generation shows that the mimic C2 is more active than C1. The different hydrogen evolution activity can be attributed to the different adsorption modes of the two [FeFe]-hydrogenase mimics on the surface of ZnS.

Covalent Functionalization of CdSe Quantum Dot Films with Molecular [FeFe] Hydrogenase Mimics for Light-Driven Hydrogen Evolution

“…From photocatalytic semiconductor–metal hybrid systems, we know that excessive catalyst loading is not necessarily beneficial to the hydrogen evolution rate, as recombination losses become dominant . A similar observation has been made for ZnS QDs and hydrogenase mimics . In contrast to our system, the loading in covalently connected QD–hydrogenase mimic systems, which showed high TONs, was in the order of 0.2 nm –2 QD surface, which is an order of magnitude less than the estimate for our system.…”

Covalent functionalization of CdSe quantum dot films with molecular [FeFe] hydrogenase mimics for light-driven hydrogen evolution

“…44 A similar observation has been made for ZnS QDs and hydrogenase mimics. 45 In contrast to our system, the loading in covalently connected QD-hydrogenase mimic systems, which showed high TONs, were in the order of 0.2 nm -2 QD surface, 21 which is an order of magnitude less than the estimate for our system. Thus, we assign the moderate TON to excessive catalyst loading to the surface.…”

Electro- and Solar-Driven Fuel Synthesis with First Row Transition Metal Complexes

“…Building on previous works combining QDs with [FeFe]-H 2 ase in solution, ,, synthetic H 2 ase mimics have also been interfaced with QDs, yielding high photoactivity for H 2 evolution. ,,,− Although generalization is not possible, it is worth noting that the formation of iron colloids from the decomposition of [FeFe]-H 2 ase-inspired carbonyl catalysts has often been observed. The resulting Fe particles may catalyze proton reduction, making careful assessment of the active species in such systems essential. ,,− …”

“…851 Although the bandgap of ZnS makes it rather unattractive for solar energy conversion (absorption at λ < 340 nm), it was also employed under similar conditions in combination with [FeFe]-H 2 ase mimics Fe 2 37 and Fe 2 38 (Figure 42), where adsorption of 0.4% (w/w) and 0.03% (w/w) of the assembly was observed, respectively. 860 IR evidence suggests that a carboxy linkage with coordinatively unsaturated Zn ions on the surface of ZnS occurs in the case of Fe 2 37, whereas an exposed sulfur group of the surface may support the adsorption of Fe 2 38. Despite lower loading, Fe 2 38 achieved higher catalytic performance than Fe 2 37 in DMF:H 2 O (9:1) containing TEOA, with respective TON H2 values of 4950 and 3400 after 30 h under 300 W irradiation without UV-cutoff filter (Table 3, entries 14 and 15).…”