Nickel-based double perovskites AA’BB’O6 are an underexplored class of oxygen evolution reaction (OER) catalysts. In particular, BaSrNiWO6 exhibits high oxygen evolution activity, attributed to the evolution of a highly OER active surface phase. The redox transformation of Ni2+(3d8) to Ni3+(3d7) combined with partial W dissolution into the electrolyte drives an in-situ reconstruction of the surface to an amorphized, NiO-like layer, promoting oxygen redox in the OER mechanism.
The surface transformations of BaSrNiWO6 are intrinsically linked to its high catalytic activity: the surface W dissolution and Ni3+ formation during cyclic voltammetry activates local lattice oxygen species for a highly efficient surface lattice oxygen evolution mechanism, as confirmed by TMA+ chemical probe studies. However, the long-range structural integrity afforded by B-site W enables the active surface to exist in a dynamic equilibrium with the bulk under operating conditions, without a cascading amorphization induced by bulk oxygen mobility. Unlike other perovskites, we propose that surface oxygen vacancies in BSNW are preferentially refilled by electrolytic OH-, due to the electronically stabilizing effect of high valence W(d0) in the B-site, which forms strong covalent bonds with neighboring O species. While surface O species can become labile in the reconstructed surface, bulk O is stabilized against diffusion. Thus, BaSrNiWO6 represents an emerging class of Ni-based double perovskites in which the electrocatalytic material properties can be modified by doping with high valence transition metals such as W. Further exploration of this vast compositional space with new doping strategies can unlock novel OER pathways and target specific surface evolutions to maximize the electrocatalytic performance of BSNW-derivatives. In addition, deeper exploration into the pH dependence of the OER activity of BSNW reveals a more complex trend than previously thought, also encompassing the kinetics of the Ni redox transformation and the extent of surface reconstruction. This new understanding can inspire further exploration into the activation mechanisms of perovskite oxides under different conditions, as our research indicates that the formation of a catalytic surface phase in BSNW is an essential prerequisite of its excellent OER activity.
Contact
Natasha Hales
PhD student, Electrocatalysis and Interfaces Group
Address: Paul Scherrer Institute PSI, 5232 Villigen PSI, Switzerland
Telephone: +41 56 310 4327
E-mail: natasha.hales@psi.ch
Original Publication
Confining surface oxygen redox in double perovskites for enhanced oxygen evolution reaction activity and Stability
Natasha Hales, Jinzhen Huang, Benjamin Heckscher Sjølin, Alvaro Garcia-Padilla,Camelia Nicoleta Borca, Thomas Huthwelker, Ivano E. Castelli, Radim Skoupy,Adam H. Clark, Michal Andrzejewski, Nicola Casati, Thomas J. Schmidt, and Emiliana Fabbri
DOI: https://doi.org/10.1002/aenm.202404560
Acknowledgement to Funding Agency
The authors gratefully acknowledge the Swiss National Science Foundation through its PRIMA grant (grant No. PR00P2_193111)