On the benchmarking of multi-junction photoelectrochemical fuel generating devices

May, Matthias M.; David, Laurent; Ohlmann, Jens; Dimroth, Frank; Krol, Roel van de; Hannappel, Thomas; Schwarzburg, Klaus

doi:10.1039/c6se00083e

Cited by 46 publications

(58 citation statements)

References 44 publications

(80 reference statements)

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“…To assess the technologies, their efficiency for carbon removal has to be estimated and compared. The typically used solar-to-fuel efficiency 20 is not a suitable measure, as it only describes the relative fraction of incident solar radiation that is converted to chemical energy. Instead, negative emission technologies based on solar energy are better assessed by the solar-to-carbon (STC) efficiency.…”

Section: Reducing the Greenhouse Effectmentioning

confidence: 99%

“…20 The distribution of energy over the chemical bonds varies for different products, yet for CO 2 removal, we are primarily interested in the number of converted CO 2 molecules. Therefore, the STC efficiencies can deviate significantly for products that have a similar energetic efficiency (Fig.…”

Section: Reducing the Greenhouse Effectmentioning

confidence: 99%

“…The current density of an ideal tandem absorber with very good catalysts can be calculated in the detailed-balance-scheme. 20 The selected product then defines the electron efficiency, η e , i.e. how many electrons are consumed for the formation of one product molecule from CO 2 and water.…”

Section: Reducing the Greenhouse Effectmentioning

confidence: 99%

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The Potential of Photoelectrochemical Carbon Sinks

May¹,

Rehfeld²

2018

Preprint

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Greenhouse gas emissions must be cut to limit global warming to 1.5-2 • C above preindustrial levels. Yet the rate of decarbonisation is currently too low to achieve this. Policy-relevant scenarios therefore rely on the permanent removal of CO 2 from the atmosphere. However, none of the envisaged technologies has demonstrated scalability to the decarbonization targets for the year 2050. In this analysis, we show that artificial photosynthesis for CO 2 reduction may deliver an efficient large-scale carbon sink. This technology is mainly developed towards solar fuels and its potential for negative emissions has been largely overlooked. With high efficiency and low sensitivity to high temperature and illumination conditions, it could, if developed towards a mature technology, present a viable approach to fill the gap in the negative emissions budget. Broader contextThe current CO 2 emission rate and its near-future development is expected to be incompatible with the worldwide carbon budget associated with a 2 • C target for global warming. Negative emission technologies are therefore becoming an increasingly important basis for climate policy scenarios, but while their scalability is necessary, it is not yet given. Biomass-based approaches for typical negative-emission targets require a significant fraction of the worldwide available arable land. We show that photoelectrochemical CO 2 reduction might be a viable alternative, that also offers a greatly reduced competition with food production. To develop this approach further, reaction paths should be optimised for carbon removal efficiency, and not for their energetic efficiency as in solar fuel applications.

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Section: Reducing the Greenhouse Effectmentioning

confidence: 99%

Section: Reducing the Greenhouse Effectmentioning

confidence: 99%

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The Potential of Photoelectrochemical Carbon Sinks

May¹,

Rehfeld²

2018

Preprint

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“…There was one historical and several recent publications on best procedures for defining configurations, light sources, and the stability criteria for measuring more artifact-free solar hydrogen conversion efficiencies in a researcher's own lab. 51,52,55,56 There is a clear need to expand these efforts and establish an official benchmarking laboratory to certify the efficiency of a device. This will reduce arguments on claims of record efficiencies and provide guidance for potential investment and industrial partners to scale up systems.…”

Section: Benchmarkingmentioning

confidence: 99%

“…Such facilities do not yet exist for photoelectrochemical or photo-driven electrochemical devices because (i) relatively few stand-alone solar fuel generators have been reported so far and (ii) establishing reliable benchmarking procedures is far more complicated than for photovoltaic devices. [51][52][53] The complications arise from having such a wide variety of components, device configurations, and reaction products to deal with, all of which would have to be transported to the benchmarking laboratory. Water splitting devices typically have multiple containers, catalysts, and electrodes.…”

Section: Benchmarkingmentioning

confidence: 99%

Perspectives on the photoelectrochemical storage of solar energy

Krol

Parkinson

2017

MRS Energy & Sustainability

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Direct photoelectrochemical water splitting offers several advantages over PV-powered electrolysis and may become the technology of choice in the future. However, significant R&D efforts and breakthroughs are needed to accomplish this goal.The sustainable production of hydrogen would be an important first step for both powering fuel cells and for enabling large-scale and technologically mature gas phase processes to reduce CO 2 and nitrogen to get desired products. Specifically, the central challenge is to produce hydrogen from water using sunlight. Photovoltaics and wind-powered electrolysis are likely to be the technology of choice to produce renewable hydrogen for the next few decades. However, the integration of light absorption and catalysis in 'direct' photoelectrolysis routes offers several advantages, such as lower current densities and better heat management, and may become technologically relevant in the second half of this century. This article discusses the research and development efforts and needed breakthroughs to achieve this goal. New chemically stable semiconductors with a band gap between 1.5 and 2.0 eV and long carrier lifetimes are urgently needed to make efficient tandem devices.Scale-up of these research level devices beyond a few cm 2 introduces mass transport limitations that require creative electrochemical engineering solutions. Last but not least, standardized methods for measuring efficiencies and stabilities need to be implemented and should lead to official benchmarking and certification laboratories to guide commercial scale up efforts. Keywords: photochemical; energy storage; energy generation RevIew DISCUSSION POINTS• Water splitting will be a central challenge for any future fossil fuel-free energy infrastructure that relies on liquid or gaseous chemical fuels.• While the main materials challenge for solar-and wind-driven electrolysis is the development of better catalysts, the main challenge for photoelectrochemical water splitting is to find new chemically stable optimal-bandgap semiconducting light absorbers.• Further progress in the development of photo-driven water splitting generators requires significant additional efforts in electrochemical engineering and the development of standardized methods for benchmarking device performance and stability.

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In Situ Characterization of Interfaces Relevant for Efficient Photoinduced Reactions

Supplie

May

Brückner

et al. 2017

Adv Materials Inter

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which he pioneered and established. In general, interfaces do not only determine electronic properties of the final device; their atomic order also highly affects growth kinetics and defect formation. Moreover, the design of solid-liquid and hybrid interfaces determines their chemical reactivity and stability. In situ monitoring of interface preparation, formation, and interfacial reactions thus promises efficient process control. Paired with a detailed understanding of interface formation mechanisms, however, the true power of in situ control is to allow for specific modification and tuning of interface formation for the device of choice. There are several excellent reviews on in situ approaches covering wide ranges of materials from basic science to applications as well as varieties of preparation and analysis techniques. [2][3][4][5][6][7][8][9][10][11] As indicated in Figure 1, this review will be focused on in situ control over interfaces of materials that are relevant for photoinduced reactions in high-efficiency solar energy conversion and sensing applications with in situ control of semiconductor/polymer/ biological interfaces. We will restrict the techniques to realistic and complex, non-ultrahigh-vacuum (UHV) ambient, where in situ control is most demandingbut also highly desired. The more complex the interfacial reactions are, the more important is the in situ characterization. Ex situ approaches can contribute to an indirect understanding of interface formation, but to understand and, finally, control the dynamic processes taking place, real-time measurements are appropriate. The challenge, we are facing, is twofold: On the one hand, increased interaction with the surrounding ambient causes higher complexity. Yet at the same time, it decreases the number of applicable techniques. On the other hand, those techniques are often elaborate and not necessarily easy to interpret. In a nutshell, we will discuss four main topics:(i) Surface preparation during growth of structures for highefficiency solar energy conversion: World-record conversion efficiencies in both photovoltaics [12,13] and solar water splitting [14] are achieved with multijunction solar cells based on epitaxial III/V compound semiconductor structures. We will discuss in situ controlled preparation Solar energy conversion and photoinduced bioactive sensors are representing topical scientific fields, where interfaces play a decisive role for efficient applications. The key to specifically tune these interfaces is a precise knowledge of interfacial structures and their formation on the microscopic, preferably atomic scale. Gaining thorough insight into interfacial reactions, however, is particularly challenging in relevant complex chemical environment. This review introduces a spectrum of material systems with corresponding interfaces significant for efficient applications in energy conversion and sensor technologies. It highlights appropriate analysis techniques capable of monitoring critical physicochemical reactions in situ during non-vacuu...

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On the benchmarking of multi-junction photoelectrochemical fuel generating devices

Cited by 46 publications

References 44 publications

The Potential of Photoelectrochemical Carbon Sinks

The Potential of Photoelectrochemical Carbon Sinks

Perspectives on the photoelectrochemical storage of solar energy

In Situ Characterization of Interfaces Relevant for Efficient Photoinduced Reactions

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