Synthesis and Characterization of Nanoscale Transition Metal Phosphates as a New Class of Electrocatalysts

Rutgers University New Brunswick, New Brunswick NJ

Investigators

Abstract

0731132 Xu, Jun John This work focuses on synthesis and characterization of nanoscale transition metal phosphates as a new class of non-noble-metal electrocatalysts for the electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The PI's laboratory recently discovered that certain transition metal phosphates exhibit excellent catalytic activities for ORR and/or OER, and some of them are capable of effectively catalyzing both ORR and OER and hence are promising bi-functional oxygen electrocatalysts. The research will build upon the initial discovery and endeavor to (1) synthesize nanoscale transition metal phosphates as a new class of non-noble-metal electrocatalysts for ORR and OER; (2) investigate the intrinsic catalytic activity and structure-property relationships of the nanoscale catalysts; and (3) probe their catalytic mechanisms using in-situ synchrotron X-ray Absorption Fine Structure (XAFS) techniques. Innovative synthesis techniques will be developed to synthesize transition metal phosphate catalysts of particle size down to a few nanometers. Judging from preliminary results, such nanoscale catalysts may give rise to rather extraordinary catalytic activities for ORR and OER. They would constitute excellent systems for probing catalytic mechanisms and expanding our understanding, and eventual use, of nanoscale non-noble-metal electrocatalysts for these reactions. Their catalytic properties and ORR and OER kinetics on them will be investigated with electrochemical techniques, and their atomic, electronic and surface structures will be investigated with XAFS techniques and correlated with catalytic properties. In-situ XAFS methods will be designed to probe their catalytic mechanisms and stability and durability issues under conditions mimicking real-operating conditions for ORR and OER in fuel cells and water electrolyzers. The intellectual merits of the study are the following. It promises to give rise to a new class of highly active nanoscale non-noble-metal electrocatalysts for ORR and OER, and advance our fundamental understanding of catalytic mechanisms and structure-property relationship of non-noble-metal electrocatalysts for these fundamentally and technologically important reactions. It also promises to contribute to the development of innovative synthesis methods for nanoscale electrocatalysts and novel in-situ characterization techniques. The broader impacts of the study are the following. The new class of nanoscale electrocatalysts could find important applications in alkaline fuel cells, water electrolysis cells, metal-air batteries and electrochemical oxygen sensors. They could especially be of value to the development of the so-called hydrogen economy, as inexpensive and viable non-noble-metal electrocatalysts for water electrolysis to produce hydrogen and for fuel cells to utilize hydrogen are among the most desirable materials to potentially enable the hydrogen economy. The study will further enhance collaboration between the PI and his institution, Rutgers University, and the senior collaborator, Dr. Mahalingam Balasubramanian, and his institution, Argonne National Laboratory. Students involved in the research will be able to utilize the state-of-the-art instrumentation at ANL and their education will be enhanced and enriched with experience at both university and national lab settings. The proposed study will offer excellent opportunities for participation by women and individuals from underrepresented groups. Moreover, the PI will invite local high school students to visit and participate in the research. The findings of the research will be incorporated into teaching materials for two new interdisciplinary courses that the PI has introduced at Rutgers University. Synthesis, physical and electrochemical characterization and studies of catalytic properties will be carried out in the PI's laboratory at Rutgers University. XAFS investigations of atomic, electronic and surface structures and molecular-level catalytic mechanisms will be carried out at the Advanced Photon Source (APS) of the Argonne National Laboratory, through collaboration between the PI and Dr. Balasubramanian, who is a beamline scientist at the APS with extensive expertise in XAFS methods and employing them to study electrochemical materials. The PI and Dr. Balasubramanian have had highly rewarding scientific collaboration in the past few years. The participation by Dr. Balasubramanian, who is fully funded through the APS, leverages the proposed effort both scientifically and financially.