Abstract
AbstractThe production of clean fuels and chemicals from waste feedstocks is an appealing approach towards creating a circular economy. However, waste photoreforming commonly employs particulate photocatalysts, which display low product yields, selectivity, and reusability. Here, a perovskite‐based photoelectrochemical (PEC) device is reported, which produces H2 fuel and simultaneously reforms waste substrates. A novel Cu30Pd70 oxidation catalyst is integrated in the PEC device to generate value‐added products using simulated solar light, achieving 60–90% product selectivity and ≈70–130 µmol cm−2 h−1 product formation rates, which corresponds to 102–104 times higher activity than conventional photoreforming systems. The single‐light absorber device offers versatility in terms of substrate scope, sustaining unassisted photocurrents of 4–9 mA cm−2 for plastic, biomass, and glycerol conversion, in either a two‐compartment or integrated “artificial leaf” configuration. These configurations enable an effective reforming of non‐transparent waste streams and facile device retrieval from the reaction mixture. Accordingly, the presented PEC platform provides a proof‐of‐concept alternative towards photoreforming, approaching more closely the performance and versatility required for commercially viable waste utilization.
Highlights
The single-light absorber device offers versatility in terms of substrate scope, sustaining unassisted photocurrents of 4–9 mA cm−2 for plastic, biomass, H2 generation, the waste substrates can be themselves photo-converted into valueadded organic products, making the entire process economically more appealing.[3]
Lead halide perovresources has emerged as a promising technology and relies on skites have emerged as state-of-the-art light absorbers and recent encapsulation approaches have allowed for their integration in photoelectrodes.[13,14,15,16]
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 and uncontrolled oxidation leading to CO2 emission or poor selectivity of the organic products.[3,4,5,6,10]
Summary
The physical separation of the oxidation and reduction reactions offered by a PEC configuration enables the individual catalyst development and process optimization for the oxidation half-reaction. Introduction of Cu into the Pd lattice causes a down-shift in the d-band center of Pd, as reported previously using quantum mechanical tools.[39] This downward shift creates favorable adsorption dynamics of reactants on the Cu30Pd70 catalyst, thereby lowering the onset potential.[28,29] Cu, having optimum oxophilicity helps to adsorb OH−, freeing active Pd sites for facile adsorption of substrates.[29,30] The OHads further aids the oxidation process and strips off the adsorbed intermediate species thereby reducing catalyst poisoning.[28,29] with the increase in Cu content, the number of Pd active sites decreases, and transport of substrates to Pd sites is inhibited by a high concentration of OHads species.[29,30,31] the roughness factor (RF) determined for Cu50Pd50 (RF = 60) is lower than that of Cu30Pd70 (RF = 140) (Figure S12, Supporting Information) These observations may explain the lower electrochemical activity for the Cu50Pd50 system, and we did not proceed further with increasing the Cu percentage in our systems. Based on the electrochemical results and understanding,[39] the best performing Cu30Pd70 MFs were chosen as the oxidation catalyst for integration into our versatile PEC systems
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