Piezoelectric Enhanced Oxygen Evolution Reaction Catalysts Using Hexagonal Nickelates
Abstract
Grant13492869-ABSTRACT:Oxygen evolution reaction catalysis (OER) is currently the rate limiting step in the electrolysis of water in,to oxygen andhydrogen. Enhancing OER activity will have an immediate impact on the production of hydrogen fuel, and the development, of metal-airrechargeable batteries and regenerative fuel cells. Advancing these technologies will benefit Naval fleet operations,, autonomous vehicles, and mobile warfighters by reducing fuel weight, and enabling point-of-use electricity generation from an abund,ant reactant (H2O).It has long been anticipated that piezoelectricity can extend OER activity beyond its current limits, but the ful,l potential of piezoelectric catalysis has yet to be realized. Piezoelectric materials develop an electrical potential when stressed, which can beused to direct charge transport and change band alignments. Unfortunately, most piezoelectric materials are not well su,ited for catalysis due to a combination of large bandgaps, high dielectric constants, and chemically inert surfaces. Improving piezo, catalysis requires optimizing the transition metal d band filling (eg ~1.2), strong orbital hybridization, and aligning the center, of the 3d band with respect to the Fermi energy and electrolyte. Increasing OER activity in piezocatalysts requires optimizing thes,e seemingly disparate property sets simultaneously, but the payoff is enhanced adsorption and desorption control beyond the limits d,efined by surface binding energies. The objective of this work is to determine the impact of piezoelectric potential on the underlyi,ng mechanismsof OER activity in order to identify the dominant mechanisms needed to enhance OER activity in piezocatalysts.BaNiO3 (B,NO) is an ideal piezocatalytic candidate identified from the theory predictions from the Materials Project Database. The OER activit,y in BaNiO3 is an order of magnitude higher than the current state-of-the-art in an alkali medium. The large OER activity in BaNiO3, is thought to stem from the flexibility in oxygen stoichiometry (BaNiO3 BaNiO2), metal oxidation state (Ni4+, Ni3+, Ni2+), and st,ructure. BNO in the P63cm phase is also predicted to have a large eij piezoelectric coefficient from 15 - 29 C/m2. The development o,f BNO piezocatalysts will advance not only our understanding of this potentially higher OER activity material but also provide an id,eal platform to study the impact of piezoelectric potential on oxygen vacancy migration, band filling, and charge compensation. The, hypothesis behind this work is that piezoelectricity can be used to enhance the OER activity of BNO if the piezoelectric potential, can drive enough oxygen vacancies to the surface of the catalyst to optimize the nickel eg filling before the potential is fully co,mpensated. Driving the oxygen vacancies to the surface will locally reduce the surface material to BaNiO2.5 (eg1) while maintaining, piezoelectric potential in the bulk BaNiO3 (eg0). The technical objectives of this work are to: 1) develop processing routes for te,xtured BaNiO3 thin films with controllable oxygen vacancy concentrations, [V_O^(..) ]; 2) Assess the electrical, piezoelectric, and, ferroelectric response of BaNiO3; 3) Track the impact of the piezoelectric potential on [V_O^(..) ] miration, nickel oxidation, an,d catalytic activity. The successful completion of this work will produce insights into the coupling between catalytic mechanisms, c,reating a knowledge based on piezocatalytic characterization and routes to optimize OER activity in novel piezocatalytic materials.A,pproved for Public Release
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 05, 2022
- Source ID
- N000142212389
Entities
People
- Lauren Garten
Organizations
- Georgia Tech Research Corporation
- Office of Naval Research
- United States Navy