Coproduction of hydrogen and lactic acid from glucose photocatalysis on band-engineered Zn1-xCdxS homojunction

Abstract

Summary Photocatalytic transformation of biomass into value-added chemicals coupled with co-production of hydrogen provides an explicit route to trap sunlight into the chemical bonds. Here, we demonstrate a rational design of Zn 1-x Cd x S solid solution homojunction photocatalyst with a pseudo-periodic cubic zinc blende (ZB) and hexagonal wurtzite (WZ) structure for efficient glucose conversion to simultaneously produce hydrogen and lactic acid. The optimized Zn 0.6 Cd 0.4 S catalyst consists of a twinning superlattice, has a tuned bandgap, and displays excellent efficiency with respect to hydrogen generation (690 ± 27.6 μmol·h −1 ·g cat. −1 ), glucose conversion (~90%), and lactic acid selectivity (~87%) without any co-catalyst under visible light irradiation. The periodic WZ/ZB phase in twinning superlattice facilitates better charge separation, while superoxide radical (⋅O 2 - ) and photogenerated holes drive the glucose transformation and water oxidation reactions, respectively. This work demonstrates that rational photocatalyst design could realize an efficient and concomitant production of hydrogen and value-added chemicals from glucose photocatalysis.

Photocatalytic Conversion of Fructose to Lactic Acid by BiOBr/Zn@SnO2 Material

“…As can be seen in Figure 9, the heterojunction of BiOBr/Zn@SnO 2 with a suitable bandgap is activated under visible light irradiation, and the photogenerated electrons generated in the conduction band reduce the absorbed oxygen to form superoxide radicals. Furthermore, the produced superoxide radicals can be continuously transformed into other reactive substances under light irradiation, such as hydroxyl radicals, which promote the conversion of fructose to lactic acid [11]. The formation of lactic acid from fructose under alkaline conditions in the photorefinery start from the ring-opening of fructose, followed by hydrolysis (transaldol) of fructose in the presence of reactive oxygen species to produce glyceraldehyde and 1,3-dihydroxyacetone.…”

“…Duan et al [9] proposed coupling heterojunctions formed by two different semiconductor materials to modify charge transfer, and Chaves et al [10] suggested that bandgap engineering should be combined with homojunction as a means to modulate the redox potential and thus achieve efficient selection for sugar oxidation. Zhao et al [11] chose Zn 1-x Cd x S to perform a series of experiments on the modulation of bandgap and redox potential. They found that the reduction in bandgap and the increase in redox potential could, to some extent, reduce the hydrogen precipitation reaction of sugars while increasing the oxidation reaction and improving the selectivity of lactic acid, but all of their studies suffer from low lactate yields.…”

“…They found that the reduction in bandgap and the increase in redox potential could, to some extent, reduce the hydrogen precipitation reaction of sugars while increasing the oxidation reaction and improving the selectivity of lactic acid, but all of their studies suffer from low lactate yields. Meanwhile, the experiments of Zhao et al [11] and Sun et al [12] revealed that •OH plays a key role in the photocatalytic conversion of sugars under weak alkaline conditions. Therefore, in the investigation of the photocatalytic conversion of fructose to lactic acid, the bandgap, redox potential, and hydroxyl radical production of the photocatalyst are essential conditions for the experiment's success [13].…”

Photocatalytic Hydrogen Production from Aqueous Solutions of Glucose and Xylose over Layered Perovskite-like Oxides HCa2Nb3O10, H2La2Ti3O10 and Their Inorganic-Organic Derivatives

“…Nowadays, typical heterogeneous photocatalysts for carbohydrates reforming are composite materials on the basis of wide-gap semiconductor oxides (predominantly, TiO 2 [ 7 , 8 , 9 , 10 , 11 ] as well as perovskites LaFeO 3 [ 12 , 13 ]), sulfides (Zn 1−x Cd x S [ 14 ], CdS/MoS 2 [ 15 , 16 ]), tungstates (BiWO 6 [ 17 ]), and metal-free compounds (g-C 3 N 4 [ 18 , 19 , 20 ]). They were tested in relation to light-driven hydrogen production from glucose [ 21 ], xylose [ 22 ], fructose [ 23 ], sucrose [ 24 ], cellulose [ 25 , 26 ], and lignocellulose [ 27 ].…”

Unlocking Selective Pathways for Glucose Photoreforming by Modulating Reaction Conditions

“…Glucose photoreforming has rapidly developed through the application of novel photocatalysts . For example, Zhao et al employed a band-engineered zinc–cadmium photocatalyst for lactic acid (LA) and hydrogen production . Bai et al produced gluconic and glucaric acid from a modified carbon nitride by introducing nitrogen defects .…”