Photocatalytic Cellulose Reforming for H₂ and Formate Production by Using Graphene Oxide-Dot Catalysts

Abstract

The mechanism of photocatalytic biomass reforming for H 2 production is far from fully understood. This study uses functionalized graphene dots with Pt-cocatalyst to reform cellulose in an alkaline solution under 1 sun illumination. Reforming of cellulose is initiated with the peeling of its constituent D-glucose units, which subsequently transform into deprotonated isosaccharinic acid (C 6 ). Further degradation of C 6 into molecules C 5 -C 1 proceeds through successive alternation of C-eliminating hydrolysis and photocatalytic oxidation of C 6 derivatives. The C 6 -C 1 species are quantitatively identified using chromatography and mass spectroscopy. The end C-containing product is predominantly HCOO − rather than HCO 3 − (or CO 2 ). The photocatalytic oxidation is accompanied by the photocatalytic reduction of water to produce H 2 . This reforming steadily produced H 2 for 6 days with a negligible rate decay, accomplishing 35% of the theoretical ultimate value for the reforming of cellulose. This study elucidates the detailed mechanism in the photocatalytic reforming of cellulose.

Reforming of Soluble Biomass and Plastic Derived Waste Using a Bias‐Free Cu30Pd70|Perovskite|Pt Photoelectrochemical Device

“…The transition from conventional suspension processes to unassisted PEC systems using a high‐performance perovskite light absorber for waste reforming provides a significant advancement towards addressing the major existing bottlenecks such as low product yield (both H 2 and oxidation products) and uncontrolled oxidation leading to CO 2 emission or poor selectivity of the organic products. [ 3–6,10 ] Our approach addresses these challenges, as Cu 30 Pd 70 |perovskite|Pt systems showcase product formation rates of up to ≈130 µmol cm −2 h −1 (normalized to geometrical irradiation area), which are ≈10 2 –10 4 times higher than previously reported photoreforming processes with established photocatalysts ( Figure ). Moreover, the high selectivity (60–90%) demonstrated by our systems towards the formation of a single value‐added product, particularly for real‐world substrates like PET bottles (≈90%), presents an attractive commercial advantage compared to typical photoreforming processes where only mixtures of non‐utilizable products are obtained.…”

“…Moreover, the high selectivity (60-90%) demonstrated by our systems towards the formation of a single value-added product, particularly for real-world substrates like PET bottles (≈90%), presents an attractive commercial advantage compared to typical photoreforming processes where only mixtures of non-utilizable products are obtained. [3][4][5]10] Thus, compared to conventional waste photoreforming, our approach provides a significant leap forward in terms of product formation rates, versatility, and selectivity, approaching some of the expected metrics for commercially viable waste utilization. [3] The two-compartment Cu 30 Pd 70 |perovskite|Pt system also provides further advantages.…”

“…passed [ ]( )= × ZnF Q (4) All the PEC measurements were performed in triplicates, except for the tests with polymeric samples in which PET powder and PET bottle have the same composition and yielded similar concentration of ethylene glycol monomers after pre-treatment. Cellulose pre-treatment, on the other hand, involves a series of steps and multiple hydrolysis reactions to yield enough volume of solution containing glucose monomers for a single PEC experiment.…”

“…[ 1–3 ] Photoreforming of abundant waste resources has emerged as a promising technology and relies on the excitation of a photocatalyst to oxidize the waste substrate, while simultaneously producing H 2 . [ 3–6 ] Thus, photoreforming is unfolding as a complementary approach to other chemical recycling strategies such as pyrolysis or gasification of biomass and plastics, which are energy‐intensive, rely often on relatively pure waste streams, and emit greenhouse gases. [ 7–9 ] In addition to H 2 generation, the waste substrates can be themselves photo‐converted into value‐added organic products, making the entire process economically more appealing.…”

“…[ 3 ] However, the generation of these organic products suffers currently from significant drawbacks in terms of low product yield and uncontrolled oxidation, either emitting undesirable CO 2 or resulting in poor selectivity where a mixture of oxidation products is obtained that cannot be separated or utilized. [ 3–5,10 ] Thus, a major challenge lies in the development of an efficient oxidation co‐catalyst to selectively transform the waste substrate in suspension. [ 11 ] Current approaches to photoreforming also mainly rely on the use of semiconductor powders, which challenge the optimization of the individual light‐absorbing and catalytic components, and display low efficiency and recyclability from the residual solid waste.…”