On Activity and Stability of Rhombohedral LaNiO3 Catalyst towards ORR and OER in Alkaline Electrolyte

Abstract

LaNiO 3 catalyst was synthesized by RHP method and sprayed onto a GDL. Electrochemical activity for oxygen reactions of asprepared GDE was evaluated under half-cell condition in oxygen-saturated 7 M KOH electrolyte. Best performance in terms of potential difference E between ORR and OER amounted 0.688 V @ 10 mA cm −2 for 20 wt% LaNiO 3 /C HSAG compared to 1 V for 20 wt% Pt/C Vulcan . Moreover, by increasing perovskite:carbon weight ratio up to 3:2, E in oxygen decreased down to 0.57 V that is the lowest value ever reported in the literature. However, phase segregation and loss in ORR activity was observed during cycling. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. [DOI: 10.1149/2.0081506eel] All rights reserved. Because of high theoretical energy density, low toxicity and attractive price, metal-air batteries and especially zinc/air system is an interesting candidate for portable and stationary energy storage applications. However, large scale commercialization is hindered by inherent drawbacks of the zinc electrode, such as poor reversibility, low energy efficiency, shape change and dendrite formation during the charging process. Moreover, resistance towards carbonate poisoning in alkaline systems and activity/stability of bi-functional catalysts for oxygen reactions have to be improved.1 Suntivich et al. found a volcano-shape correlation between σ * -orbital occupation (e g ) of different La-based perovskites and their activity for both ORR 2 and OER 3 reactions. Among the investigated systems, LaNiO 3 appears to be one of the best candidates in terms of bifunctionality. It is meanwhile wellknown that the reaction rate of these catalysts strongly depends on particle size, intrinsic electronic conductivity, phase stability and preparation method. By co-precipitation of metal nitrate precursors with 1 M NaOH, extremely low Tafel slope value of 43 mV dec −1 (2RT/3F) for OER was measured at a pure Lanthanum Nickel Oxide phase powder without addition of binder materials. 4 This excellent value was attributed to a high carrier density (holes) and dominant presence of Ni 2+ at the surface, and to a large amount of oxygen vacancies. Not only oxidation state of the transition metal but also roughness factor of the powder material is primordial. By using a chlorine-modified precipitation route 5 to further oxidized Ni 2+ to Ni 3+ , Singh et al.,6 measured a seven times larger roughness factor in comparison to that of the product yielded by traditional precipitation method. 4 Bulk perovskite materials are generally synthesized by (i) solid-phase sintering at high temperature, typically by T > 1278 K, ...

Activity and Stability of Ruddlesden–Popper‐Type Lan+1NinO3n+1 (n=1, 2, 3, and ∞) Electrocatalysts for Oxygen Reduction and Evolution Reactions in Alkaline Media

“…The OER activities of LaNiO 3 and La 4 Ni 3 O 10.26 continuously decrease over 15 cycles, whereas those of La 2 NiO 4.27 and La 3 Ni 2 O 7.15 settle after slight degradation over the first six cycles. [14] This stability issue may be minimized in our future work by optimizingt he catalysta nd binder formulation to improve the degradation rate in alkaline media. [10,13] The ORR activities show no such leveling-off behavior;a ll compounds exhibit analogous declines in performance over 15 cycles.…”

“…The loss of electrocatalytic activityh as often been attributed to carbon corrosion and/ort he degradation of the oxide matrix. [14] This stability issue may be minimized in our future work by optimizingt he catalysta nd binder formulation to improve the degradation rate in alkaline media.…”

Enhanced Bifunctional Oxygen Catalysis in Strained LaNiO3 Perovskites

“…Both pre-and post-test XRD and specific area measurements (see SI) were similar, suggesting minimal instability and phase segregation. 13b, 18 Using XRD reciprocal space mapping (RSM) to determine in-plane lattice parameters, we found all films were coherently strained except for LNO on LSAO, which was relaxed and substantially strain free (ε = 0 to -0.3%) due to a small critical thickness for strain relaxation. While an additional range of strain states from ε = -1.2 to 0% was also generated through strain relaxation by increasing the thickness of LNO on LAO from 10 to 100 nm (see Supplementary Fig.…”

Nanoscale Perovskites as Catalysts and Supports for Direct Methanol Fuel Cells

“…Hence,a sakey practical nuancew orth noting,s oa st oe nhance the possibility of stimulating synergistic charget ransfer, conductive carbon speciest ended to be introduced intot hese systems. [26] As such, the resulting LaMO 3 -carbon hybrid yielded not only an enhanced ORR activity but also al ower onset potential as compared with both perovskite and carbonc ontrols.…”

“…Whereas doping with Sr atoms causeda ggregation of Ni particles, the corresponding doping of the As ite with Ca increased the number of surfacea nd bulk oxygen vacancies, thereby effectively not only reducing coking but also increasing system durability and stability. [26] AO xygen reduction reaction (ORR)…”