Solar reforming

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Solar reforming is the sunlight-driven conversion of diverse carbon waste resources (including solid, liquid, and gaseous waste streams such as biomass, plastics, industrial by-products, atmospheric carbon dioxide, etc.) into sustainable fuels (or energy vectors) and value-added chemicals.<ref name=":0">Bhattacharjee, Subhajit; Linley, Stuart; Reisner, Erwin (2024-01-30). "Solar reforming as an emerging technology for circular chemical industries". Nature Reviews Chemistry. 8 (2): 87–105. doi:10.1038/s41570-023-00567-x. ISSN 2397-3358. PMID 38291132. S2CID 267332161.</ref> It encompasses a set of technologies (and processes) operating under ambient and aqueous conditions, utilizing solar spectrum to generate maximum value.<ref name=":0" /> Solar reforming offers an attractive and unifying solution to address the contemporary challenges of climate change and environmental pollution by creating a sustainable circular network of waste upcycling, clean fuel (and chemical) generation and the consequent mitigation of greenhouse emissions (in alignment with the United Nations Sustainable Development Goals).

Background

The earliest sunlight-driven reforming (now referred to as photoreforming or PC reforming which forms a small sub-section of solar reforming; see Definition and classifications section) of waste-derived substrates involved the use of TiO2 semiconductor photocatalyst (generally loaded with a hydrogen evolution co-catalyst such as Pt). Kawai and Sakata from the Institute for Molecular Science, Okazaki, Japan in the 1980s reported that the organics derived from different solid waste matter could be used as electron donors to drive the generation of hydrogen gas over TiO2 photocatalyst composites.<ref>Kawai, Tomoji; Sakata, Tadayoshi (1980-07-31). "Conversion of carbohydrate into hydrogen fuel by a photocatalytic process". Nature. 286 (5772): 474–476. Bibcode:1980Natur.286..474K. doi:10.1038/286474a0. ISSN 1476-4687. S2CID 4356641.</ref><ref>Kawai, Tomoji; Sakata, Tadayoshi (January 1981). "Photocatalytic hydrogen production from water by the decomposition of poly-vinylchloride, protein, algae, dead insects, and excrement". Chemistry Letters. 10 (1): 81–84. doi:10.1246/cl.1981.81. ISSN 0366-7022.</ref> In 2017, Wakerley, Kuehnel and Reisner at the University of Cambridge, UK demonstrated the photocatalytic production of hydrogen using raw lignocellulosic biomass substrates in the presence of visible-light responsive CdS|CdOx quantum dots under alkaline conditions.<ref>Wakerley, David W.; Kuehnel, Moritz F.; Orchard, Katherine L.; Ly, Khoa H.; Rosser, Timothy E.; Reisner, Erwin (2017-03-13). "Solar-driven reforming of lignocellulose to H2 with a CdS/CdOx photocatalyst". Nature Energy. 2 (4): 1–9. doi:10.1038/nenergy.2017.21. ISSN 2058-7546. S2CID 100128646.</ref> This was followed by the utilization of less-toxic, carbon-based, visible-light absorbing photocatalyst composites (for example carbon-nitride based systems) for biomass and plastics photoreforming to hydrogen and organics by Kasap, Uekert and Reisner.<ref>Kasap, Hatice; Achilleos, Demetra S.; Huang, Ailun; Reisner, Erwin (2018-09-19). "Photoreforming of Lignocellulose into H 2 Using Nanoengineered Carbon Nitride under Benign Conditions". Journal of the American Chemical Society. 140 (37): 11604–11607. doi:10.1021/jacs.8b07853. ISSN 0002-7863. PMID 30153420. S2CID 52111870.</ref><ref>Uekert, Taylor; Kasap, Hatice; Reisner, Erwin (2019-09-25). "Photoreforming of Nonrecyclable Plastic Waste over a Carbon Nitride/Nickel Phosphide Catalyst". Journal of the American Chemical Society. 141 (38): 15201–15210. doi:10.1021/jacs.9b06872. ISSN 0002-7863. PMC 7007225. PMID 31462034.</ref> In addition to variations of carbon nitride, other photocatalyst composite systems based on graphene oxides, MXenes, co-ordination polymers and metal chalcogenides were reported during this period.<ref>Wang, Jiu; Kumar, Pawan; Zhao, Heng; Kibria, Md Golam; Hu, Jinguang (2021). "Polymeric carbon nitride-based photocatalysts for photoreforming of biomass derivatives". Green Chemistry. 23 (19): 7435–7457. doi:10.1039/D1GC02307A. ISSN 1463-9262. S2CID 238644248.</ref><ref>Wu, Xinxing; Zhao, Heng; Khan, Mohd Adnan; Maity, Partha; Al-Attas, Tareq; Larter, Stephen; Yong, Qiang; Mohammed, Omar F.; Kibria, Md Golam; Hu, Jinguang (2020-10-19). "Sunlight-Driven Biomass Photorefinery for Coproduction of Sustainable Hydrogen and Value-Added Biochemicals". ACS Sustainable Chemistry & Engineering. 8 (41): 15772–15781. doi:10.1021/acssuschemeng.0c06282. ISSN 2168-0485. S2CID 225149072.</ref><ref>Rao, Cheng; Xie, Maoliang; Liu, Sicong; Chen, Runlin; Su, Hang; Zhou, Lan; Pang, Yuxia; Lou, Hongming; Qiu, Xueqing (2021-09-22). "Visible Light-Driven Reforming of Lignocellulose into H 2 by Intrinsic Monolayer Carbon Nitride". ACS Applied Materials & Interfaces. 13 (37): 44243–44253. doi:10.1021/acsami.1c10842. ISSN 1944-8244. PMID 34499461. S2CID 237472526.</ref><ref name=":2">Pichler, Christian M.; Bhattacharjee, Subhajit; Rahaman, Motiar; Uekert, Taylor; Reisner, Erwin (2021-08-06). "Conversion of Polyethylene Waste into Gaseous Hydrocarbons via Integrated Tandem Chemical–Photo/Electrocatalytic Processes". ACS Catalysis. 11 (15): 9159–9167. doi:10.1021/acscatal.1c02133. ISSN 2155-5435. PMC 8353629. PMID 34386271.</ref><ref>Guan, Lijiang; Cheng, Guang; Tan, Bien; Jin, Shangbin (2021). "Covalent triazine frameworks constructed via benzyl halide monomers showing high photocatalytic activity in biomass reforming". Chemical Communications. 57 (42): 5147–5150. doi:10.1039/D1CC01102B. ISSN 1359-7345. PMID 33899846. S2CID 233400735.</ref><ref>Nguyen, Van-Can; Nimbalkar, Dipak B.; Nam, Le D.; Lee, Yuh-Lang; Teng, Hsisheng (2021-05-07). "Photocatalytic Cellulose Reforming for H 2 and Formate Production by Using Graphene Oxide-Dot Catalysts". ACS Catalysis. 11 (9): 4955–4967. doi:10.1021/acscatal.1c00217. ISSN 2155-5435. S2CID 233564941.</ref><ref>Cao, Bingqian; Wan, Shipeng; Wang, Yanan; Guo, Haiwei; Ou, Man; Zhong, Qin (2022-01-01). "Highly-efficient visible-light-driven photocatalytic H2 evolution integrated with microplastic degradation over MXene/ZnxCd1-xS photocatalyst". Journal of Colloid and Interface Science. 605: 311–319. doi:10.1016/j.jcis.2021.07.113. ISSN 0021-9797. PMID 34332406.</ref><ref>Nagakawa, Haruki; Nagata, Morio (2021-12-02). "Highly Efficient Hydrogen Production in the Photoreforming of Lignocellulosic Biomass Catalyzed by Cu,In-Doped ZnS Derived from ZIF-8". Advanced Materials Interfaces. 9 (2). doi:10.1002/admi.202101581. ISSN 2196-7350. S2CID 244880250.</ref> A major limitation of PC reforming is the use of conventional harsh alkaline pre-treatment conditions (pH >13 and high temperatures) for polymeric substrates such as condensation plastics, accounting for more than 80% of the operation costs.<ref name=":3" /> This was circumvented with the introduction of a new chemoenzymatic reforming pathway in 2023 by Bhattacharjee, Guo, Reisner and Hollfelder, which employed near-neutral pH, moderate temperatures for pre-treating plastics and nanoplastics.<ref>Bhattacharjee, Subhajit; Guo, Chengzhi; Lam, Erwin; Holstein, Josephin M.; Rangel Pereira, Mariana; Pichler, Christian M.; Pornrungroj, Chanon; Rahaman, Motiar; Uekert, Taylor; Hollfelder, Florian; Reisner, Erwin (2023-09-20). "Chemoenzymatic Photoreforming: A Sustainable Approach for Solar Fuel Generation from Plastic Feedstocks". Journal of the American Chemical Society. 145 (37): 20355–20364. doi:10.1021/jacs.3c05486. ISSN 0002-7863. PMC 10515630. PMID 37671930.</ref> In 2020, Jiao and Xie reported the photocatalytic conversion of addition plastics such as polyethylene and polypropylene to high energy-density to C2 fuels over a Nb2O5 catalyst under natural conditions.<ref>Jiao, Xingchen; Zheng, Kai; Chen, Qingxia; Li, Xiaodong; Li, Yamin; Shao, Weiwei; Xu, Jiaqi; Zhu, Junfa; Pan, Yang; Sun, Yongfu; Xie, Yi (September 2020). "Photocatalytic Conversion of Waste Plastics into C 2 Fuels under Simulated Natural Environment Conditions". Angewandte Chemie International Edition. 59 (36): 15497–15501. doi:10.1002/anie.201915766. ISSN 1433-7851. PMID 32003512. S2CID 210983540.</ref>

The photocatalytic process (referred to as PC reforming; see Categorization and configurations section below) offers a simple, one-pot and facile deployment scope, but has several major limitations, making it challenging for commercial implementation.<ref name=":3">Uekert, Taylor; Pichler, Christian M.; Schubert, Teresa; Reisner, Erwin (2020-11-30). "Solar-driven reforming of solid waste for a sustainable future". Nature Sustainability. 4 (5): 383–391. Bibcode:2020NatSu...4..383U. doi:10.1038/s41893-020-00650-x. ISSN 2398-9629. S2CID 227236618.</ref> In 2021, sunlight-driven photoelectrochemical (PEC) systems/technologies operating with no external bias or voltage input were introduced by Bhattacharjee and Reisner at the University of Cambridge.<ref name=":4">Bhattacharjee, Subhajit; Andrei, Virgil; Pornrungroj, Chanon; Rahaman, Motiar; Pichler, Christian M.; Reisner, Erwin (2021-10-27). "Reforming of Soluble Biomass and Plastic Derived Waste Using a Bias-Free Cu 30 Pd 70 |Perovskite|Pt Photoelectrochemical Device". Advanced Functional Materials. 32 (7). doi:10.1002/adfm.202109313. ISSN 1616-301X.</ref> These PEC reforming (see Categorization and configurations section) systems reformed diverse pre-treated waste streams (such as lignocellulose and PET plastics) to selective value-added chemicals with the simultaneous generation of green hydrogen, and achieving areal production rates 100-10000 times higher than conventional photocatalytic processes.<ref name=":4" /> In 2023, Bhattacharjee, Rahaman and Reisner extended the PEC platform to a solar reactor which could reduce greenhouse gas CO2 to different energy vectors (CO, syngas, formate depending on the type of catalyst integrated) and convert waste PET plastics to glycolic acid at the same time.<ref name=":5">Bhattacharjee, Subhajit; Rahaman, Motiar; Andrei, Virgil; Miller, Melanie; Rodríguez-Jiménez, Santiago; Lam, Erwin; Pornrungroj, Chanon; Reisner, Erwin (2023-01-09). "Photoelectrochemical CO2-to-fuel conversion with simultaneous plastic reforming". Nature Synthesis. 2 (2): 182–192. doi:10.1038/s44160-022-00196-0. ISSN 2731-0582. S2CID 255686581.</ref> This further inspired the direct capture and conversion of CO2 to products from flue gas and air (direct air capture) in a PEC reforming process (with simultaneous plastic conversion).<ref>Kar, Sayan; Rahaman, Motiar; Andrei, Virgil; Bhattacharjee, Subhajit; Roy, Souvik; Reisner, Erwin (2023-07-19). "Integrated capture and solar-driven utilization of CO2 from flue gas and air". Joule. 7 (7): 1496–1514. doi:10.1016/j.joule.2023.05.022. ISSN 2542-4351.</ref> Choi and Ryu demonstrated a polyoxometallate-medated PEC process to achieve biomass conversion with unassisted hydrogen production in 2022.<ref>Choi, Yuri; Mehrotra, Rashmi; Lee, Sang-Hak; Nguyen, Trang Vu Thien; Lee, Inhui; Kim, Jiyeong; Yang, Hwa-Young; Oh, Hyeonmyeong; Kim, Hyunwoo; Lee, Jae-Won; Kim, Yong Hwan; Jang, Sung-Yeon; Jang, Ji-Wook; Ryu, Jungki (2022-10-03). "Bias-free solar hydrogen production at 19.8 mA cm−2 using perovskite photocathode and lignocellulosic biomass". Nature Communications. 13 (1): 5709. doi:10.1038/s41467-022-33435-1. ISSN 2041-1723. PMC 9529942. PMID 36192405.</ref> Similarly, Pan and Chu, in 2023 reported a PEC cell for renewable formate production from sunlight, CO2 and biomass-derived sugars.<ref>Pan, Yuyang; Zhang, Huiyan; Zhang, Bowen; Gong, Feng; Feng, Jianyong; Huang, Huiting; Vanka, Srinivas; Fan, Ronglei; Cao, Qi; Shen, Mingrong; Li, Zhaosheng; Zou, Zhigang; Xiao, Rui; Chu, Sheng (2023-02-23). "Renewable formate from sunlight, biomass and carbon dioxide in a photoelectrochemical cell". Nature Communications. 14 (1): 1013. Bibcode:2023NatCo..14.1013P. doi:10.1038/s41467-023-36726-3. ISSN 2041-1723. PMC 9950059. PMID 36823177.</ref> These developments has led solar reforming (and electroreforming, where renewable electricity drives redox processes; see Caterogization and configurations section) to gradually emerge as an active area of exploration.

Concept and considerations

Definition and classifications

Solar reforming is the sunlight-driven transformation of waste substrates to valuable products (such as sustainable fuels and chemicals) as defined by scientists Subhajit Bhattacharjee, Stuart Linley and Erwin Reisner in their 2024 Nature Reviews Chemistry article where they conceptualized and formalized the field by introducing its concepts, classification, configurations and metrics.<ref name=":0" /> It generally operates without external heating and pressure, and also introduces a thermodynamic advantage over traditional green hydrogen or CO2 reduction fuel producing methods such as water splitting or CO2 splitting, respectively. Depending on solar spectrum utilization, solar reforming can be classified into two categories: “solar catalytic reforming” and “solar thermal reforming”.<ref name=":0" /> Solar catalytic reforming refers to transformation processes primarily driven by ultraviolet (UV) or visible light.<ref name=":0" /> It also includes the subset of ‘photoreforming’ encompassing utilization of high energy photons in the UV or near-UV region of the solar spectrum (for example, by semiconductor photocatalysts such as TiO2). Solar thermal reforming, on the other hand, exploits the infrared (IR) region for waste upcycling to generate products of high economic value.<ref name=":0" /> An important aspect of solar reforming is value creation, which means that the overall value creation from product formation must be greater than substrate value destruction.<ref name=":0" /> In terms of deployment architectures, solar catalytic reforming can be further categorized into: photocatalytic reforming (PC reforming), photoelectrochemical reforming (PEC reforming) and photovoltaic-electrochemical reforming (PV-EC reforming).<ref name=":0" />

Advantages over conventional waste recycling and upcycling processes

Solar reforming offers several advantages over conventional methods of waste management or fuel/chemical production. It offers a less energy-intensive and low carbon alterative to methods of waste reforming such as pyrolysis and gasification which require high energy input.<ref name=":0" /> Solar reforming also provides several benefits over traditional green hydrogen production methods such as water splitting (H2O → H2 + ½O2, ΔG° = 237 kJ mol−1). It offers a thermodynamic advantage over water splitting by circumventing the energetically and kinetically demanding water oxidation half reaction (E⁰ = +1.23 V vs. reversible hydrogen electrode (RHE)) by energetically neutral oxidation of waste-derived organics (CxHyOz + (2x−z)H2O → (2x−z+y/2)H2 + xCO2; ΔG° ~0 kJ mol−1).<ref name=":0" /> This results in better performance in terms of higher production rates, and also translates to other similar processes which depend on water oxidation as the counter reaction such as CO2 splitting. Furthermore, concentrated streams of hydrogen produced from solar reforming is safer than explosive mixtures of oxygen and hydrogen (from traditional water splitting), that otherwise require additional separation costs.<ref name=":0" /> The added economic advantage of forming two different valuable products (for example, gaseous reductive fuels and liquid oxidative chemicals) simultaneously makes solar reforming suitable for commercial applications.<ref name=":0" />

Solar reforming metrics

Solar reforming encompasses a range of technological processes and configurations and therefore, suitable performance metrics can evaluate the commercial viability. In artificial photosynthesis, the most common metric is the solar-to-fuel conversion efficiency (ηSTF) as shown below, where ‘r’ is the product formation rate, ‘ΔG’ is the Gibbs free energy change during the process, ‘A’ is the sunlight irradiation area and ‘P’ is the total light intensity flux.<ref name=":0" /><ref name=":6" /> The ηSTF can be adopted as a metric for solar reforming but with certain considerations. Since the ΔG values for solar reforming processes are very low (ΔG ~0 kJ mol‒1), this makes the ηSTF per definition close to zero, despite the high production rates and quantum yields. However, replacing the ΔG for product formation (during solar reforming) with that of product utilisation (|ΔGuse|; such as combustion of the hydrogen fuel generated) can give a better representation of the process efficiency.<ref name=":0" />

<math>\eta_{\mathrm{STF}}=\frac{\mathrm{r}_{\mathrm{SR}}\left(\mathrm{mol} \cdot \mathrm{s}^{-1}\right) \times \Delta \mathrm{G}_{\mathrm{SR}}\left(\mathrm{J} \cdot \mathrm{mol}^{-1}\right)}{\mathrm{P}_{\text {total }}\left(\mathrm{W} \cdot \mathrm{m}^{-2}\right) \times \mathrm{A}\left(\mathrm{m}^2\right)}</math>

Since solar reforming is highly dependent on the light harvester and its area of photon collection, a more technologically relevant metric is the areal production rate (rareal) as shown, where ‘n’ is the moles of product formed, ‘A’ is the sunlight irradiation area and ‘t’ is the time.<ref name=":0" />

<math>\mathrm{r}_{\text {areal}}=\frac{\mathrm{n}_{\text {product}}(\mathrm{mol})}{\mathrm{A}\left(\mathrm{m}^2\right) \times \mathrm{t}(\mathrm{h})}</math>

Although rareal is a more consistent metric for solar reforming, it neglects some key parameters such as type of waste utilized, pre-treatment costs, product value, scaling, other process and separation costs, deployment variables, etc.<ref name=":0" /> Therefore, a more adaptable and robust metric is the solar-to-value creation rate (rSTV) which can encompass all these factors and provide a more holistic and practical picture from the economic or commercial point of view.<ref name=":0" /> The simplified equation for rSTV is shown below, where Ci and Ck are the costs of the product ‘i’ and substrate ‘k’, respectively. ‘Cp’ is the pre-treatment cost for the waste substrate ‘k’, and ‘ni’ and ‘nk’ are amounts (in moles) of the product ‘i’ formed and substrate ‘k’ consumed during solar reforming, respectively. Note that the metric is adaptable and can be expanded to include other relevant parameters as applicable.<ref name=":0" />

<math>r_{\mathrm{STV}}= \frac{ {\textstyle \sum_{i=1}^M \displaystyle C_i ($mol^{-1})\times n_i(mol)} - {\textstyle \sum_{k=1}^N \displaystyle \bigl(C_k+C_p\bigr) ($mol^{-1})\times n_k (mol)}}{A (m^2)\times t(h)}{}</math>

Categorization and configurations

Solar reforming depends on the properties of the light absorber and the catalysts involved, and their selection, screening and integration to generate maximum value. The design and deployment of solar reforming technologies dictates the efficiency, scale and target substrates/products. In this context, solar reforming (more specifically, solar catalytic reforming) can be classified into three architectures:<ref name=":0" />

Introduction of 'Photon Economy'

An important concept introduced in the context of solar reforming is the ‘photon economy’, which, as defined by Bhattacharjee, Linley and Reisner, is the maximum utilization of all incident photons for maximizing product formation and value creation.<ref name=":0" /> An ideal solar reforming process is one where the light absorber can absorb incident UV and visible light photons with maximum quantum yield, generating high charge carrier concentration to drive redox half reactions at maximum rate. On the other hand, the residual, non-absorbed low-energy IR photons may be used for boosting reaction kinetics, waste pre-treatment or other means of value creation (for example, desalination,<ref>Pornrungroj, Chanon; Mohamad Annuar, Ariffin Bin; Wang, Qian; Rahaman, Motiar; Bhattacharjee, Subhajit; Andrei, Virgil; Reisner, Erwin (2023-11-13). "Hybrid photothermal–photocatalyst sheets for solar-driven overall water splitting coupled to water purification". Nature Water. 1 (11): 952–960. doi:10.1038/s44221-023-00139-9. ISSN 2731-6084.</ref> etc.). Therefore, proper light and thermal management through various means (such as using solar concentrators, thermoelectric modules, among others) is encouraged to have both an atom economical and photon economical approach to extract maximum value from solar reforming processes.

Reception and media

The technological advancements in solar reforming garnered widespread interest in recent years. The works from scientists at Cambridge on PC reforming of raw lignocellulosic biomass or pre-treated polyester plastics to produce hydrogen and organics attracted attention of several stakeholders.<ref>"Scientists harness solar power to produce clean hydrogen from biomass". Bio Fuel Daily. Retrieved 2024-02-13.</ref><ref>"Covid: PPE 'could be recycled' with help of sunlight". 2020-12-22. Retrieved 2024-02-13.</ref><ref>"Scientists harness solar power to produce clean hydrogen from biomass". EurekAlert!. Retrieved 2024-02-13.</ref> The recent technological breakthrough leading to the development of high-performing solar powered reactors (PEC reforming) for the simultaneous upcycling of greenhouse gas CO2 and waste plastics to sustainable products received widespread acclaim and was highlighted in several prominent national and international media outlets.<ref>"Could waste plastic become a useful fuel source?". BBC. 2023-03-14. Retrieved 2024-02-13.</ref><ref>Theil, Michele (2023-01-23). "Scientists have found a way to convert plastics and CO2 into sustainable fuels using solar power". The Big Issue. Retrieved 2024-02-13.</ref><ref>"Plastic waste and CO2 converted into hydrogen and feedstock chemical using sunlight". Chemistry World. Retrieved 2024-02-13.</ref><ref>"Solar reactor converts both CO2 and plastic waste into useful products". New Atlas. 2023-01-10. Retrieved 2024-02-13.</ref><ref>"Solar-powered system converts plastic and greenhouse gases into sustainable fuels". University of Cambridge. 2023-01-09. Retrieved 2024-02-13.</ref><ref>"Solar-powered system converts plastic and greenhouse gases into sustainable fuels". ScienceDaily. Retrieved 2024-02-13.</ref><ref>"Solar Powered Machine Turns CO2 and Waste Plastic Into Valuable Fuel". Futurism. Retrieved 2024-02-13.</ref><ref>"Converting plastics and greenhouse gases into sustainable energy | Technology". Labroots. Retrieved 2024-02-13.</ref><ref>محمود, عبد الحكيم. "ابتكار نظام ثنائي يعمل بالطاقة الشمسية يحول البلاستيك وغازات الاحتباس الحراري إلى وقود مستدام". الجزيرة نت (in العربية). Retrieved 2024-02-13.</ref><ref>Patel, Prachi (2023-01-12). "Solar powered reactor converts plastic and CO2 into fuel". Retrieved 2024-02-13.</ref><ref>"BREAKTHROUGH! Indian researchers at Cambridge university offer solution to global warming and plastic pollution". TimesNow. 2023-01-24. Retrieved 2024-02-13.</ref><ref>Video | The Importance Of Solving The Biggest Environmental Challenges Through Research & Technology, retrieved 2024-02-13</ref><ref>Bhatia, Anisha (2023-03-17). "Two Indian Scientists On The Importance Of Solving The Biggest Environmental Challenges Through Research And Technology". NDTV-Dettol Banega Swasth Swachh India. Retrieved 2024-02-13.</ref><ref>"Scientists use 'miracle material' to convert plastic waste into sustainable fuel". The Independent. 2023-01-09. Retrieved 2024-02-13.</ref><ref>"In Breakthrough, 2 Indian Scientists Offer Answers To These Global Issues". NDTV.com. Retrieved 2024-02-13.</ref> Solar reforming processes primarily developed in Cambridge were also selected as “one of the eleven great ideas from British universities that could change the world” by Sunday Times (April 2020 edition)<ref>Forster, Rosie Kinchen and Katherine (2024-02-13). "Reasons to be cheerful: 11 great ideas from British universities that could change the world". The Times. ISSN 0140-0460. Retrieved 2024-02-13.</ref> and featured in the UK Prime Minister’s Speech on Net Zero, “Or the researchers at Cambridge who pioneered a new way to turn sunlight into fuel”<ref>"PM speech on Net Zero: 20 September 2023". GOV.UK. 2023-09-20. Retrieved 2024-02-13.</ref> (indicating solar reforming which was a major subset of the broader research activities at Cambridge).

Outlook and future scope

Solar reforming is currently in the development phase and the scalable deployment of a particular solar reforming technology (PC, PEC or PV-EC) would depend on a variety of factors. These factors include deployment location and sunlight variability/intermittency, characteristics of the chosen waste stream, viable pre-treatment methods, target products, nature of the catalysts and their lifetime, fuel/chemical storage requirements, land use versus open water sources, capital and operational costs, production and solar-to-value creation rates, and governmental policies and incentives, among others.<ref name=":0" /> Solar reforming may not be only limited to the conventional chemical pathways discussed, and may also include other relevant industrial processes such as light-driven organic transformations, flow photochemistry, integration with industrial electrolysis, among others.<ref name=":0" /> The products from conventional solar reforming such as green hydrogen or other platform chemicals have a broad value-chain. It is also now understood that sustainable fuel/chemical producing technologies of the future will rely on biomass, plastics and CO2 as key carbon feedstocks to replace fossil fuels.<ref>"Roadmap Chemie 2050". VCI Online (in German). 2019-10-09. Retrieved 2024-02-13.{{cite web}}: CS1 maint: unrecognized language (link)</ref> Therefore, with sunlight being abundant and the cheapest source of energy, solar reforming is well-positioned to drive decarbonization and facilitate the transition from a linear to circular economy in the coming decades.<ref name=":0" />

See also

References

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