Strategic Energy Alliance is a cross-campus effort of the Precourt Institute for Energy.

Optimized organic semiconductors as electrocatalysts

Strategic Energy Research Consortium (SERC)

OSC catalyst reaction image

Figure 1.  Working principle of doped-polymeric organic semiconductor (OSC) catalyst in energy conversion reactions. Ox/Red = oxidation/reduction; ET = Electron Transfer. Electrochemical doping process of the neutral polymeric OSC (step 1), and the electron transfer reaction between the doped polymeric OSC (steps 2+3).

Background

Cost-effective and carbon-neutral energy storage and conversion technologies that can efficiently convert between chemical energy and electrical energy are needed in the transition from fossil fuels to renewable sources of power. Many of these conversions require catalysts that contain precious metals, such as Platinum (Pt), and many have an electrode design that is complex. An alternative to precious metal catalysts are metal-free organic materials that are inherently scalable, easily processed, in geo-abundance, and potentially recyclable (see Figure 1). An ideal electrocatalyst would have an active site where the electronic, chemical, and physical properties are tunable. The wide chemical tuneability of organic polymeric catalysts may provide a solution. At present, however, organic catalysts demonstrate lower catalytic activity than precious metal catalysts and often require multi-phase electrode design to achieve stability during operation.

Project Goals

This project aims to characterize the fundamental relationship between chemical structure and catalytic activity in organic-based catalysts to develop low-cost, scalable, and recyclable catalysts for heterogeneous electrocatalysis. Design principles for polymeric organic semiconductors (OSC) will be developed to enable enhancement of other energy conversion and fuel production reactions, such as electrolytic hydrogen production and CO2 reduction. The goal is to produce the polymeric OSC on several grams scale for initial testing of the catalyst in technologically relevant applications.

Approach

This work aims to develop efficient electrocatalysts based on polymeric OSC for affordable and recyclable catalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Specific tasks aim to:

  • Study the fundamental electrochemical properties of promising polymeric OSCs to help define which chemical structures of polymeric OSC show the highest catalytic activity for energy conversion reactions dealing with molecular oxygen (ORR, OER).
  • Identify chemical structures that enable reversible electrochemical doping in aqueous electrolytes to drive electron transfer reactions.
  • Define chemical structures that act as efficient functional groups to ensure a rapid transport of ionic charge carriers as well as gas molecules to achieve bulk activity of the catalyst with high mass-transport properties.
  • Test if a single-phase electrode based on polymeric OSC maintain its reactivity during operation in acidic and alkaline aqueous electrolytes.
  • Test if devices can be recycled by solvent extraction processes to recover the catalyst for a second life.

This approach will pave the way for the design of single-phase electrodes that can be processed from solution, lowering the cost of production of the electrode.

Team Members

Alberto Salleo 
Alberto Salleo is a Professor of Materials Science and Engineering at Stanford University. His research focuses on novel materials and processing techniques for large-area and flexible electronic/photonic devices. He develops polymeric materials for electronics, bioelectronics, and biosensors and electrochemical devices for neuromorphic computing. Professor Salleo also conducts structure/property studies of polymeric semiconductors, nano-structured and amorphous materials in thin films, and advanced characterization techniques for soft matter. 

William Chueh
William Chueh is an Associate Professor of Materials Science and Engineering at Stanford University. The central question unifying his group’s research is: “can we understand and engineer redox reactions at the levels of electrons, ions, molecules, particles and devices using a bottom-up approach?” The approach of Chueh and his group integrates novel synthesis, fabrication, characterization, modeling and analytics to understand molecular pathways and interfacial structure, and to bridge fundamentals to energy storage and conversion technologies by establishing new design rules. 

Other Team members/post-doc and students
Alexander Giovannitti, Tyler Mefford, Ana De La Fuente Durán, Ilaria Denti, Adam Marks, Emily Penn, Allen Yu-Lun Liang, and Lily Turaskis