Scalable Photocatalyst Panels for Photoreforming of Plastic, Biomass and Mixed Waste in Flow

Abstract

Solar-driven reforming uses sunlight and a photocatalyst to generate H 2 fuel from waste at ambient temperature and pressure. However, it faces practical scaling challenges such as photocatalyst dispersion and recyclability, competing light absorption by the waste solution, slow reaction rates and low conversion yields. Here, the immobilisation of a noble-metalfree carbon nitride/nickel phosphide (CN x j Ni 2 P) photocatalyst on textured glass is shown to overcome several of these limitations. The 1 cm 2 CN x j Ni 2 P panels photoreform plastic, biomass, food and mixed waste into H 2 and organic molecules with rates comparable to those of photocatalyst slurries. Furthermore, the panels enable facile photocatalyst recycling and novel photoreactor configurations that prevent parasitic light absorption, thereby promoting H 2 production from turbid waste solutions. Scalability is further verified by preparing 25 cm 2 CN x j Ni 2 P panels for use in a custom-designed flow reactor to generate up to 21 μmol H 2 m À 2 h À 1 under "real-world" (seawater, low sunlight) conditions. The application of inexpensive and readily scalable CN x j Ni 2 P panels to photoreforming of a variety of real waste streams provides a crucial step towards the practical deployment of this technology.

Conversion of Polyethylene Waste into Gaseous Hydrocarbons via Integrated Tandem Chemical–Photo/Electrocatalytic Processes

“…Beside the batch reaction, we also conducted studies applying a recently reported flow setup using a photocatalyst panel, 31 which allowed the utilization of the pure, colored PE decomposition solution, as the light absorption losses are minimized in this configuration ( Figure S7 ). The flow setup employed a flow cell with the mounted photocatalyst panel, where the photocatalyst was deposited by dropcasting a catalyst suspension on a frosted glass sheet (25 cm 2 ; Figure S8 ).…”

“…The optimization of the dropcasting process was discussed in our previous study. 31 The reaction solution was pumped through the flow cell, while the photocatalyst sheet was irradiated from the back. Back irradiation of the photocatalyst panel allows light to reach the photocatalyst without being absorbed by the colored reaction solution.…”

“…The photocatalytic flow setup and the preparation of the utilized catalyst glass sheets were already described elsewhere. 31 The first step is the preparation of the photocatalyst sheets, employing frosted glass (5 × 5 cm 2 ) that was cleaned by sonication with isopropyl alcohol and acetone for 15 min each, followed by drying under a N 2 stream. NCN CN x |Pt or P25|Pt was dispersed in ethanol (20 mg mL –1 ) by ultrasonication (10 min, pulses of 30 s at 100% amplitude followed by 5 s pauses), and 1 vol % Nafion solution (5 wt %) was added to the resulting mixture.…”

Recent Progress in the Chemical Upcycling of Plastic Wastes

“…To boost the photocatalytic activity, a CN x /Ni 2 P panel instead of NPs as the photocatalyst was constructed by immobilizing the CN x /Ni 2 P material on textured glass, and the purposes of the new configuration were to ease the recycling of the catalyst and obviate the competing light absorption by the matrix. [54] Upscaled panels of 25 cm 2 area of the photocatalyst were employed to transform various waste solutions such as cellulose, PET, and municipal solid waste in flow at ambient temperature and pressure under simulated solar light in 0.5 m KOH solution to generate satisfactory yields of H 2 gas. Moreover, approximately 50 % of the photocatalytic activity was maintained under even milder conditions (seawater, 0.2 sunlight irradiation).…”

Recent Advancements in Photocatalytic Valorization of Plastic Waste to Chemicals and Fuels

“…Furthermore, to overcome practical scaling challenges of traditional powder photocatalyst systems, such as sedimentation, difficult to recycle, and competing light absorption with waste solution, Reisner and co-workers have immobilized the CN x |Ni 2 P photocatalyst on textured glass (Supplementary Figure 4I) (Uekert et al, 2020b). It has been found that the 1 cm 2 square CN x |Ni 2 P panel can photoconvert waste plastic into H 2 and organic molecules with rates comparable to those of photocatalyst slurries, while enable facile photocatalyst recycling.…”