Activity-Stability Relationships in Oxide Electrocatalysts for Water Electrolysis

Abstract

The oxygen evolution reaction (OER) is one of the key kinetically limiting half reactions in electrochemical energy conversion. Model epitaxial catalysts have emerged as a platform to identify structure-function-relationships at the atomic level, a prerequisite to establish advanced catalyst design rules. Previous work identified an inverse relationship between activity and the stability of noble metal and oxide OER catalysts in both acidic and alkaline environments: The most active catalysts for the anodic OER are chemically unstable under reaction conditions leading to fast catalyst dissolution or amorphization, while the most stable catalysts lack sufficient activity. In this perspective, we discuss the role that epitaxial catalysts play in identifying this activity-stability-dilemma and introduce examples of how they can help overcome it. After a brief review of previously observed activity-stability-relationships, we will investigate the dependence of both activity and stability as a function of crystal facet. Our experiments reveal that the inverse relationship is not universal and does not hold for all perovskite oxides in the same manner. In fact, we find that facet-controlled epitaxial La0.6Sr0.4CoO3-δ catalysts follow the inverse relationship, while for LaNiO3-δ, the (111) facet is both the most active and the most stable. In addition, we show that both activity and stability can be enhanced simultaneously by moving from La-rich to Ni-rich termination layers. These examples show that the previously observed inverse activity-stability-relationship can be overcome for select materials and through careful control of the atomic arrangement at the solid-liquid interface. This realization re-opens the search for active and stable catalysts for water electrolysis that are made from earth-abundant elements. At the same time, these results showcase that additional stabilization via material design strategies will be required to induce a general departure from inverse stability-activity relationships among the transition metal oxide catalysts to ultimately grant access to the full range of available oxides for OER catalysis.

Coordination Inversion of the Tetrahedrally Coordinated Ru4f Surface Complex on RuO2(100) and Its Decisive Role in the Anodic Corrosion Process

“…In several studies, ,,,, it has been proposed that activity and stability are intimately coupled in the acidic OER: the higher the activity, the lower the stability and vice versa. Recently, this relationship has been shown to be not universal and did not hold for some perovskite oxides . For the case of acidic OER over RuO 2 (110), this interrelation of activity and stability was subject to a first-principles study, disclosing that both processes share indeed a common reaction intermediate, namely, a RuO 4 surface species.…”

“…Recently, this relationship has been shown to be not universal and did not hold for some perovskite oxides. 68 For the case of acidic OER over RuO 2 (110), this interrelation of activity and stability was subject to a first-principles study, 16 disclosing that both processes share indeed a common reaction intermediate, namely, a RuO 4 surface species. The LOER mechanism can safely be ruled out for RuO 2 .…”

Deeper mechanistic insights into epitaxial nickelate electrocatalysts for the oxygen evolution reaction

“…For example, for LaNiO 3 , the (111) facet is both more active and more stable than other facets, a trend that could be revealed studying epitaxial thin films synthesized on differently oriented substrates. 69 Epitaxial thin films also enable the fabrication of material combinations with hybrid properties by interfacing different perovskite oxides with unit cell thickness control. 22 Such heterostructures offer even more degrees of freedom to engineer stable and active electrocatalysts that overcome the inverse stability–activity relationship.…”

Recent Advances and New Challenges: Two-Dimensional Metal–Organic Framework and Their Composites/Derivatives for Electrochemical Energy Conversion and Storage

“…Electrocatalysis is a surface reaction, in which the catalytic performance of the catalyst depends on their surface properties to a large extent. In this regard, 2D pristine MOFs and their composites are the most prominent electrocatalysts with favorable International Journal of Energy Research properties, such as ultrahigh thickness, enhanced conductivity, high surface to volume atom ratio, tunable oxidation state, and exposed active sites which are shown in Figure 9 [162][163][164]. This section presents advanced 2D MOF-based electrocatalysts for the HER, OER, ORR, CO 2 RR, and UOR.…”