Fast and vast: An upscaled materials acceleration platform for sustainable hydrogen

Effective storage solutions are indispensable for harnessing scattered and intermittent solar energy. The materials field has been employing materials acceleration platforms to expedite materials discovery. Zhang et al.'s recent work in Nature Synthesis introduced high-throughput nanojunction synthesis and automated photocatalytic screening, which pinpointed the most efficient molecular donor-acceptor combinations. Furthermore, their study bridged the gap between automated screening and large-scale production, boosting the development of scalable sustainable fuel production. Effective storage solutions are indispensable for harnessing scattered and intermittent solar energy. The materials field has been employing materials acceleration platforms to expedite materials discovery. Zhang et al.'s recent work in Nature Synthesis introduced high-throughput nanojunction synthesis and automated photocatalytic screening, which pinpointed the most efficient molecular donor-acceptor combinations. Furthermore, their study bridged the gap between automated screening and large-scale production, boosting the development of scalable sustainable fuel production. In the growing awareness of climate change and the quest for sustainable energy sources, light-harvesting technologies have emerged as critical innovations, particularly in the field of solar energy.1Nijsse F.J.M.M. Mercure J.-F. Ameli N. Larosa F. Kothari S. Rickman J. Vercoulen P. Pollitt H. The momentum of the solar energy transition.Nat. Commun. 2023; 146542https://doi.org/10.1038/s41467-023-41971-7Crossref Scopus (23) Google Scholar,2Pourasl H.H. Barenji R.V. Khojastehnezhad V.M. Solar energy status in the world: A comprehensive review.Energy Rep. 2023; 10: 3474-3493https://doi.org/10.1016/j.egyr.2023.10.022Crossref Scopus (34) Google Scholar Given the necessity to sustain living and production activities beyond daylight hours, integrating additional storage solutions with solar power becomes crucial. The potential for producing fuels through solar energy is promising and can be seamlessly integrated into current infrastructure. Yet, advancing solar fuel technologies toward commercial viability requires achieving high cost efficiency, excellent scalability, and robust durability. Such progress requires intensive engineering and optimization, complemented by innovations in materials technology. Undoubtedly, these efforts require iterative experimentation and additional work in digitizing and analyzing data against the backdrop of big data. Recently, the materials research community has witnessed the rise of materials acceleration platforms (MAPs) that combine robotic synthesis and the characterization of materials with AI-driven data analysis.3Wang T. Li R. Ardekani H. Serrano-Luján L. Wang J. Ramezani M. Wilmington R. Chauhan M. Epps R.W. Darabi K. et al.Sustainable materials acceleration platform reveals stable and efficient wide-bandgap metal halide perovskite alloys.Matter. 2023; 6: 2963-2986https://doi.org/10.1016/j.matt.2023.06.040Abstract Full Text Full Text PDF Scopus (11) Google Scholar,4Zhang J. Hauch J.A. Brabec C.J. Toward Self-Driven Autonomous Material and Device Acceleration Platforms (AMADAP) for Emerging Photovoltaics Technologies.Acc. Chem. Res. 2024; 57: 1434-1445https://doi.org/10.1021/acs.accounts.4c00095Crossref PubMed Scopus (3) Google Scholar These platforms are designed to significantly speed up the processes of materials discovery and optimization, showing particular promise in identifying suitable organic molecules for light-harvesting applications. However, the implementation of comprehensive screening beyond automated synthesis presents notable challenges due to the need for application-specific characterization methods that vary across different material classes. Moreover, as these systems are generally developed for small-scale operations, it remains uncertain whether scaling up would yield consistent results. A pioneering recent study by Zhang et al., featured in Nature Synthesis, introduces a new method for the discovery and scaling up of synthetic nanomaterials.5Zhang W. Yu M. Liu T. Cong M. Liu X. Yang H. Bai Y. Zhu Q. Zhang S. Gu H. et al.Accelerated discovery of molecular nanojunction photocatalysts for hydrogen evolution by using automated screening and flow synthesis.Nat. Synth. 2024; 3: 595-605https://doi.org/10.1038/s44160-024-00494-9Crossref Scopus (6) Google Scholar By employing high-throughput nanojunction synthesis and automated photocatalytic screening techniques, the research team efficiently pinpointed and enhanced molecular nanojunction photocatalysts, achieving excellent solar water splitting rates. The study further demonstrates successful upscaling via flow synthesis, seamlessly connecting small-scale trials to large-scale production without sacrificing performance. Cooper, Zhu, and their team's work on small-molecule nanojunction photocatalysts featured a combinatorial strategy using a library of donor-acceptor molecular pairs (Figure 1A). Employing the Hantzsch pyridine condensation reaction, they synthesized 26 different acceptors and combined these with six electron-rich donors to generate 156 binary donor-acceptor combinations and 32 single-component systems processed via ultrasonic nanoprecipitation. Their high-throughput screening, facilitated by an automated system that managed solution preparation, parallel photolysis, and gas chromatography analysis, allowed for the simultaneous evaluation of 48 samples. Following a first-round screening that led to further testing with structural analogues of MTPA-CA (3-(4-(bis(4-methoxyphenyl)amino)phenyl)-2-cyanoacrylic acid) and a select group of CNP (2,6-bis(4-cyanophenyl)-4-(4′-fluoro1,1′-biphenyl-4-yl)pyridine-3,5-dicarbonitrile) acceptors, the optimal photocatalyst combination of MTPA-CA was pinpointed. Notably, this comprehensive testing of more than 200 photocatalysis experiments was achieved within a mere 3 days. It is widely recognized that the properties and effectiveness of organic semiconductors are determined by their chemical structure as well as their nanomorphology. In industries such as organic electronics and pharmaceuticals, initial successes identified through high-throughput screening at a small scale frequently face difficulties when transitioning to large-scale production. Therefore, it is crucial to effectively translate the results from high-throughput screening to scaled-up production processes to ensure the viability and consistency of the final products. A significant accomplishment of Zhang et al.'s study was the application of the flow-based flash nanoprecipitation process, which utilizes a multi-inlet vortex mixer for scaled-up synthesis. This technique initially optimized the most effective donor-acceptor pair, yielding an impressive hydrogen evolution rate of 330.3 mmol h−1 g−1 under full-spectrum and 289 mW cm−2 conditions and 157.7 mmol h−1 g−1 under air mass 1.5 G irradiation. Subsequent scale-up efforts demonstrated a 200-fold increase in production volume while maintaining comparable efficacy. The scaled-up molecular nanojunctions preserved their one-dimensional nanofiber architecture, vital for effective charge separation and high photocatalytic activity, with enhanced crystallization and phase purity significantly contributing to their superior hydrogen evolution performance. After synthesizing and characterizing the photocatalysts, the research team utilized quantum chemistry calculations to unravel the mechanisms driving their activity. The hydrogen evolution activity, plotted as a function of the donor-acceptor binding energy, revealed a volcano plot, indicating that the most active catalysts were situated within a narrow energy window of 0.2–0.3 eV. This observation suggests a pivotal design principle—maintaining moderate binding energy between donor and acceptor molecules enhances charge transport efficiency in light-active organic materials. The findings from Zhang et al. have significant implications for photocatalytic water splitting. This combination forms a next-generation platform that not only facilitates the rapid identification and refinement of new photocatalysts but also ensures that these innovations are scalable and directly translatable to industrial applications. Furthermore, the research draws attention to the significant but underexplored potential of small-molecule organic semiconductors for photocatalytic applications, an area that is far less represented in the literature compared with polymeric systems. The precision in achieving molecular nanojunctions that exhibit high crystallinity and efficient charge separation underscores a promising pathway for the development of photocatalytic solar fuel production using small-molecule organic photocatalysts. Furthermore, extended photocatalytic tests are recommended to determine the long-term stability of the molecular heterojunctions, addressing a common challenge in the field of organic electronics. The adoption of MAPs is viewed as a transformative step in accelerating materials discovery. The automation inherent in MAPs not only reduces labor-intensive processes but also can address a prevalent issue: the under-collection of data in research institutes. Data facilitated by automated multi-modal characterization are richer in information and could be more reliable.6Vogler M. Busk J. Hajiyani H. Jørgensen P.B. Safaei N. Castelli I.E. Ramirez F.F. Carlsson J. Pizzi G. Clark S. et al.Brokering between tenants for an international materials acceleration platform.Matter. 2023; 6: 2647-2665https://doi.org/10.1016/j.matt.2023.07.016Abstract Full Text Full Text PDF Scopus (10) Google Scholar However, several challenges remain, including high initial costs and a large skill gap required for setup, which could deter widespread adoption. Moreover, repeated practices that are wasteful and environmentally harmful could exacerbate environmental impacts. To mitigate these issues, incorporating computer vision technologies like high-resolution microscopy and hyperspectral imaging could help reduce resource-heavy production processes.7Siemenn A.E. Aissi E. Sheng F. Tiihonen A. Kavak H. Das B. Buonassisi T. 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This work was supported by funding from an Engineering and Physical Sciences Research Council (EPSRC) grant (H2CAT, EP/V012932/1). S.D.S. acknowledges the Royal Society and Tata Group (UF150033). The authors declare no competing interests.