The US Department of Energy announced $75 million in funding to renew the Joint Center for Artificial Photosynthesis (JCAP), a DOE Energy Innovation Hub originally established in 2010 with the goal of harnessing solar energy for the production of fuel. (Earlier post.)
Under the renewal plan, the five-year-old center would receive funding for an additional five years of research, subject to Congressional appropriations. JCAP researchers are focused on achieving the major scientific breakthroughs needed to produce liquid transportation fuels from a combination of sunlight, water, and carbon dioxide, using artificial photosynthesis.
JCAP will capitalize on advanced capabilities developed during its initial five years of research, including sophisticated characterization tools and unique automated high-throughput experimentation that can quickly make and screen large libraries of materials to identify components for artificial photosynthesis systems.
JCAP seeks to discover new ways to produce energy-dense fuels, such as hydrogen and carbon-based fuels, using only sunlight, water, and carbon dioxide as inputs. Artificial photosynthesis, once achieved and scaled up, could be significantly more efficient than biofuel production processes and would not require arable land, agricultural feedstock, or substantial inputs of energy or water. Success could ultimately drive commercial development of solar-fuel systems designed from inception to be easily deployable almost anywhere.
The research program involves eight core projects:
Light Capture and Conversion. This project focuses on the discovery and development of semiconducting materials for solar light absorption. The key objective for the project is to identify stable, efficient Earth-abundant semiconductors that can provide sufficient voltage for water-splitting and carbon dioxide reduction chemistries.
Topics of research in the program include: investigations of novel materials as photoanodes for water oxidation and photocathodes for hydrogen production and carbon dioxide reduction, design of protection schemes against photocorrosion, theoretical modeling and computational simulations of band gaps and corrosion behavior, and development of new experimental techniques for characterization of optoelectronic properties of semiconductors.
Heterogeneous Catalysis. The focus of this project is to discover and to develop heterogeneous catalysts for solar-fuel generation. Using theory, modern surface-science methods, and synchrotron-based techniques, JCAP researchers seek to understand the reaction pathways and the elementary steps of the hydrogen and oxygen evolutions reactions to facilitate the design of new, Earth-abundant catalysts for solar-fuels production.
Current research efforts in the Heterogeneous Catalysis project involve the design and study of new oxygen- and hydrogen-evolving materials and development of novel surface characterization methods for in situ measurements.
Molecular Catalysis. The Molecular Catalysis Project involves directed discovery of homogeneous catalysts for the key reactions involved in solar-fuel generation: oxidation of water to oxygen, reduction of water to hydrogen, and reduction of carbon dioxide to carbon-based liquid fuels and selective intermediates.
The program focuses on development of transition-metal complexes that are inspired by the natural photosynthetic enzymes such as nitrogenases, hydrogenases, and the oxygen-evolving complex of photosystem II with the goal of designing catalysts that are chemically stable, active, and highly selective for specific chemical targets.
Current research activities include the synthesis and characterization of carbon-dioxide reducing electrocatalysts that are based on Earth-abundant metals and studies of the reaction kinetics of carbon-dioxide reduction with active catalysts.
High-Throughput Experimentation. This project focuses on automated, high-throughput discovery of materials that can act as light absorbers or catalysts for solar-fuel generation. The HTE project employs high-speed, combinatorial techniques that can produce new alloys from Earth-abundant elements, rapid screening methods that can identify high-performing light absorbers and catalysts, and surface-science analysis tools that can characterize the structure and composition of promising materials.
Research in the HTE project involves development of new fabrication systems for combinatorial synthesis of alloys, automated tools for optical and electrochemical activity screening, and information systems for storage and analysis of data.
Catalyst and Light Absorber Benchmarking. The Benchmarking program serves as a community resource for the performance validation of electrocatalysts and photocatalysts. The need for benchmarking exists because testing methods employed by researchers in the solar-fuels research field are far from standardized (different light sources, electrolyte solutions, pH ranges, etc.), making it difficult to cross-compare the performance of different materials, and more difficult still to determine which materials are truly the most promising. Objective identification of the most promising materials for integration into a solar-fuels device is therefore a critical focus of research efforts within JCAP.
Molecular and Nanoscale Interfaces. A major obstacle towards the development of a viable artificial photosynthetic systems for water splitting to hydrogen and oxygen, or the conversion of carbon dioxide and water to liquid fuel, involves the inefficient charge transport between light absorbers and catalysts and, in particular, between the sites of water oxidation and fuel-generating half-reactions.
To address these challenges, the Molecular and Nanoscale Interfaces Project aims to couple light absorbers, catalysts, and half-reactions for optimal control of the rate, yield, and energetics of electron and proton flow at the nanoscale, so that complete macroscale artificial photosynthetic systems can achieve maximum conversion of solar photon energy into the chemical energy of a fuel.
Key areas of research in the Molecular and Nanoscale Interfaces group includes the design of molecular “tool kits” for interfacing homogeneous catalysts to electrode surfaces, the development of solid-solid interfacing schemes to couple heterogeneous catalysts to electrode surfaces, and mechanistic studies of charge-transport behavior at these interfaces.
Membrane and Mesoscale Assembly. This project seeks to develop methods for orienting, assembling, and interconnecting nanoscale functional assemblies containing catalysts, light absorbers, and support matrices, into fully functional photoelectrochemical systems. A key objective of work in the program is to develop a knowledge foundation of structure-function relationships for photoelectrochemical layers that allows for prediction and control of transport phenomena in macroscopic solar-fuel generation systems. Towards the goal, research in the Membranes and Mesoscale Assembly program is directed towards the engineering of membranes that satisfy the structural and chemical stability, gas/fuel permeability, and ionic-conductivity requirements for solar-fuels devices as well as towards experimental and theoretical investigations of structured catalyst/light-absorber/membrane assemblies that maximize solar-energy conversion efficiencies.
Scale-Up and Prototyping. The focus of the Scale-Up and Prototyping Project is to construct fully functional, macroscopic solar-fuels generation systems to guide the overall research effort of JCAP. The design of prototypes on a large size scale is needed to identify the critical effects that bubbles, reactant input and product output flows, optical issues, and other such issues will have on the performance of a solar-fuels generator.
Work in the Scale-Up and Prototyping program informs the JCAP scientific efforts as to where key performance levers are and also identifies gaps revealed by real-world implementation of an integrated solar-fuels generator based on artificial photosynthesis. Current development work in the program is focused on the design of prototype models that use dual-light absorber (tandem) configuration cells.
JCAP—which brings together many of the world’s top researchers in the field of artificial photosynthesis—is led by the California Institute of Technology in partnership with Lawrence Berkeley National Laboratory, and operates research sites at both institutions.
A Southern California site is located at the Caltech campus in Pasadena, while a Northern California site operates at Lawrence Berkeley National Laboratory in Berkeley. Additional partners include SLAC National Accelerator Laboratory; the University of California, Irvine; and the University of California, San Diego.
JCAP is one of several Energy Innovation Hubs established by the Department of Energy beginning in 2010. The Energy Innovation Hubs are major integrated research centers, drawing together researchers from multiple institutions and varied technical backgrounds. They are modeled after the strong scientific management approaches typified by the Manhattan Project, the Lincoln Lab at MIT, which developed radar, AT&T’s Bell Laboratories, which developed the transistor, as well as the successful DOE Bioenergy Research Centers established during the Bush Administration to pioneer advanced techniques in biotechnology, including biofuels.