Many scientists have become increasingly concerned with the course and status of science-related policies in recent years, and these concerns have only grown in the past months as governments have had to face a global pandemic. As experts in our respective fields, scientists have an obligation and an opportunity to help to inform science policy. We are a group of early-career scientists, four UC Irvine graduate students and one postdoc, who have seen great value in getting involved with political discourse and science policy. Each of us has been drawn to science policy for different reasons. For some, the decision to get involved has been deeply personal; Evelyn Valdez-Ward, for example, advocates for undocumented and marginalized scientists like herself. Some of us are concerned that, although we are only now beginning our research careers, our research could quite literally disappear with the onset of climate change if political action is not taken. Those of us who work in public health have seen the need to be engaged politically so that we can communicate with our communities, politicians, and funding agencies about how critical research is for our country's future health and safety. The current pandemic has likely altered the course of research in this Researchers eager to inform policy with science should seek out the pathways that are available for engaging with lawmakers at the state, local, or national level-while making sure to understand the nuances of political discourse.

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The U.S. Department of Energy recently announced its first Energy Earthshot on Clean Hydrogen, with a cost target of $1/kg-H2 by 2031. Assuming future utility-scale grid electricity prices from photovoltaics ($0.02/kWh), 80% of the cost of H2 would come from performing low-temperature water electrolysis at its thermoneutral voltage, with zero additional overpotential. This fact motivates alternative, less-expensive means of using light to generate mobile charge carriers than photovoltaics, and reactor designs with exceedingly low capital costs, like those we recently invented. Systems using low capital cost reactors benefit from low-voltage operation, which represents a paradigm shift from current state-of-the-art electrolyzers that aim to operate at high current densities. Analytical models predict that solar photocatalytic water splitting inherently operates at low voltages through use of an ensemble of optically thin photoabsorbers each operating at a low rate. Collectively the ensemble exhibits larger overall solar-to-hydrogen conversion efficiencies in comparison to optically thick designs. In efforts to attain these predicted higher efficiencies, we are performing detailed studies on the properties of state-of-the-art doped SrTiO3 and BiVO4 photocatalyst particles. During my talk, I will share our recent efforts in atomic-layer deposited ultrathin oxide coatings to impart redox selectivity and materials stability, single-photocatalyst-particle current–potential behavior and mobile charge carrier properties, and atomic-level information on dopant distributions and materials interfaces obtained from electron microscopies and X-ray spectroscopies. Collectively, our discoveries provide new design guidelines and additional research pathways for the development of effective composite materials to serve as active components in techno-economically viable artificial photosynthetic devices.

Particle suspension reactors for solar water splitting are capable of generating hydrogen at a cost that is competitive with hydrogen produced from steam methane reforming.1-3 Our team has validated a reactor design that resembles Nature’s Z-scheme where two stacked and connected photocatalyst particle suspension reactor beds together drive overall solar water splitting.3 Electron (and proton) management between the beds occurs by transport of a redox shuttle through a nanoporous separator. Efficient designs require that the redox shuttle is selectively oxidized and reduced at the particles that drive H2 evolution and O2 evolution, respectively. By device physics numerical simulations we showed that even for highly efficient reactor designs (10% STH efficiency) redox shuttle transport between the beds can be sustained with only passive diffusion.3 In my presentation I will report on our team’s recent progress on this design. Using finite-element numerical analyses we modelled and simulated the transient mass transport processes, light absorption, electrochemical kinetics, gas crossover, and thermal transport in the proposed reactor. Experimentally, we synthesized, characterized, and evaluated the photo(electro)chemical performance of the most promising photocatalyst nanocrystallites (BiVO4, WO3, and Rh-doped SrTiO3) as mesoporous thin films and as particles in model reactors, and in the presence of several different redox shuttles and at various pH values. For H2-evolving Rh-doped SrTiO3, we demonstrated that in the presence of Fe(II) the limiting rate of Fe(III) reduction decreases and the rate of H2 evolution increases; however, these desired processes occurred along with undesired Fe(III) reduction and undesired H2 oxidation. Introduction of Ru cocatalysts enhanced performance by increasing the rate of H2 evolution and to a lesser extent undesired Fe(III) reduction. For O2-evolving WO3, we showed that O2 does not interfere with collection of electrons and that selectivity toward Fe(III) reduction is possible at moderate concentrations of Fe(III). Overall, results from several studies using a series of redox shuttles and photocatalyst particles will be presented. Collectively, our efforts represent strides toward achieving a high-level of techno-economic viability in solar water splitting reactors. Acknowledgments: This work was supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Fuel Cell Technologies Incubator Program under Award No. DE-EE0006963 and Lawrence Berkeley National Laboratory under Contract No. DE-AC02-05CH11231. References: D. James, G. N. Baum, J. Perez and K. N. Baum, Technoeconomic Analysis of Photoelectrochemical (PEC) Hydrogen Production, Directed Technologies Inc., (US DOE Contract no. GS-10F-009J), Arlington, VA, 2009. A. Pinaud, J. D. Benck, L. C. Seitz, A. J. Forman, Z. Chen, T. G. Deutsch, B. D. James, K. N. Baum, G. N. Baum, S. Ardo, H. Wang, E. Miller, and T. F. Jaramillo, Energy & Environmental Science, 2013, 6, 1983–2002. Bala Chandran, S. Breen, Y. Shao, S. Ardo, and A. Z. Weber, Energy & Environmental Science, 2017, Accepted Manuscript, DOI: 10.1039/C7EE01360D.