The 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 H 2 fuel and simultaneously reforms waste substrates. A novel Cu 30 Pd 70 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 10 2 -10 4 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-ofconcept alternative towards photoreforming, approaching more closely the performance and versatility required for commercially viable waste utilization.

The chemical inertness of polyethylene makes chemical recycling challenging and motivates the development of new catalytic innovations to mitigate polymer waste. Current chemical recycling methods yield a complex mixture of liquid products, which is challenging to utilize in subsequent processes. Here, we present an oxidative depolymerization step utilizing diluted nitric acid to convert polyethylene into organic acids (40% organic acid yield), which can be coupled to a photo- or electrocatalytic decarboxylation reaction to produce hydrocarbons (individual hydrocarbon yields of 3 and 20%, respectively) with H 2 and CO 2 as gaseous byproducts. The integrated tandem process allows for the direct conversion of polyethylene into gaseous hydrocarbon products with an overall hydrocarbon yield of 1.0% for the oxidative/photocatalytic route and 7.6% for the oxidative/electrolytic route. The product selectivity is tunable with photocatalysis using TiO 2 or carbon nitride, yielding alkanes (ethane and propane), whereas electrocatalysis on carbon electrodes produces alkenes (ethylene and propylene). This two-step recycling process of plastics can use sunlight or renewable electricity to convert polyethylene into valuable, easily separable, gaseous platform chemicals.

Solar-driven conversion of CO2 and plastics into value-added products provides a potential sustainable route towards a circular economy, but their simultaneous conversion in an integrated process is yet to be accomplished. Here, we introduce a versatile photoelectrochemical (PEC) platform for CO2 conversion which is coupled to the reforming of plastic. The perovskite-based photocathode enables the integration of different CO2 reduction catalysts such as molecular cobalt porphyrin, Cu91In9 alloy, and formate dehydrogenase, which produce CO, syngas, and formic acid, respectively. The Cu27Pd73 alloy anode selectively reforms polyethylene terephthalate (PET) plastics into glycolic acid. The overall single lightabsorber PEC system operates with the help of an internal chemical bias and under zero applied voltage. The system performs similarly to bias-free, dual-light absorber tandems and shows ~10-100 fold higher production rates than photocatalytic suspension processes. This finding demonstrates efficient CO2-to-fuel conversion coupled to plastic-to-chemical PEC conversion as a promising sustainable technology powered by sunlight.

Biomass Transformation In article number 2109313, Erwin Reisner and co‐workers introduce a bias‐free thin‐film device, which can reform diverse waste streams, including biomass, industrial by‐products, and plastic waste, into value‐added chemicals and clean H2 fuel using sunlight. The versatile prototype demonstrates the potential of photoelectrochemical assemblies toward waste valorization, approaching the high product rates and selectivity required for commercial implementation.

Metrics & MoreArticle Recommendations CONSPECTUS:The sustainable synthesis of fuels and chemicals is key to attaining a carbon-neutral economy. This can be achieved by mimicking the light-harvesting and catalytic processes occurring in plants. Solar fuel production is commonly performed via established approaches, including photovoltaic−electrochemical (PV−EC), photoelectrochemical (PEC), and photocatalytic (PC) systems. A recent shift saw these systems evolve into integrated, compact panels, which suit practical applications through their simplicity, scalability, and ease of operation. This advance has resulted in a suite of apparently similar technologies, including the so-called artificial leaves and PC sheets. In this Account, we compare these different thin film technologies based on their micro-and nanostructure (i.e., layered vs particulate), operation principle (products occurring on the same or different sides of the panel), and product/reaction scope (overall water splitting and CO 2 reduction, or organics, biomass, and waste conversion).For this purpose, we give an overview of developments established over the past few years in our laboratory. Two light absorbers are generally required to overcome the thermodynamic challenges of coupling water oxidation to proton or CO 2 reduction with good efficiency. Hence, tandem artificial leaves combine a lead halide perovskite photocathode with a BiVO 4 photoanode to generate syngas (a mixture of H 2 and CO), whereas PC sheets involve metal-ion-doped SrTiO 3 and BiVO 4 particles for selective formate synthesis from CO 2 and water. On the other hand, only a single light absorber is needed for coupling H 2 evolution to organics oxidation in the thermodynamically less demanding photoreforming process. This can be performed by immobilized carbon nitride (CN x ) in the case of PC sheets or by a single perovskite light absorber in the case of PEC reforming leaves. Such systems can be integrated with a range of inorganic, molecular, and biological catalysts, including metal alloys, molecular cobalt complexes, enzymes, and bacteria, with low overpotentials and high catalytic activities toward selective product formation. This wide reaction scope introduces new challenges toward quantifying and comparing the performance of different systems. To this end, we propose new metrics to evaluate the performance of solar fuel panels based on the areal product rates and commercial product value. We further explore the key opportunities and challenges facing the commercialization of thin film technologies for solar fuels research, including performance losses over larger areas and catalyst/device recyclability. Finally, we identify emerging applications beyond fuels, where such light-driven panels can make a difference, including the waste management, chemical synthesis, and pharmaceutical industries. In the long term, these aspects may facilitate a transition toward a light-driven circular economy.