Structure‐property Relationship of Double Perovskite Oxide towards Trifunctional Electrocatalytic Activity: Strategy for Designing and Development

Abstract

In the present scenario, the paramount significant roles of various heterogeneous catalysts stimulate the modern technologies to underpin the benchmark requirements for the generation of sustainable energy by reducing toxic fossil fuel emissions. Such critical role necessitates further development of cost‐effective highly efficient and earth‐abundant multifunctional or trifunctional electrocatalysts to promote the advancement of electrochemical overall water splitting performances, yet it is extremely desirable. In this review context, we present the development of double perovskite (DP) oxides as robust trifunctional catalysts for electrochemical oxygen evolution reaction (OER), oxygen reduction reaction (ORR) and hydrogen evolution reactions (HER) by rational design of multiple cationic redox sites with stoichiometric oxygen amount. Particularly, we highlight the importance of the structural modifications via doping, surface structure and oxygen stoichiometry as key parameters to tune the electrocatalytic activities and understand the insight into activity and mechanism of this oxide family. This perspective also describes controlled synthesis protocols including the surface structure of double perovskite oxides are key techniques for realizing a correlation between structure‐activity relationships of these materials. Finally, it is concluded by outlining the several aspects of optimization strategies and computational opportunities can expand the future scope of double perovskite oxides as robust trifunctional electrocatalysts.

Intrinsic Specific Activity Enhancement for Bifunctional Electrocatalytic Activity toward Oxygen and Hydrogen Evolution Reactions via Structural Modification of Nickel Organophosphonates

“…In recent years, researchers are mainly focused to fabricate such electrocatalysts based on different classes of framework materials such as metal–organic frameworks (MOFs), hybrid open-frameworks, as well as different metal oxides, hydroxides, sulfides, nitrides, phosphides, and phosphonates. − Among them, transition-metal phosphonates can be considered as one of the most effective electrocatalysts, owing to their structural diversity, tunable morphology, long-term stability, and cost-effective generation. − …”

Investigation of the Role of 3d-4d Elements in a Disordered Double Perovskite toward Efficient Photocatalytic Energy Conversion and Electrochemical Energy-Storage Behaviors

“…Furthermore, the charge-storage mechanism in the DP system could be more complete as the cation oxidation/reduction process leads to the interconversion of O 2– ions to OH – ions into the structure. − ,,,, The excellent photocatalytic water oxidation and electrochemical supercapacitor performances of the present materials could be attributed to the combine intrinsic activity as well as the synergistic effect of both 3 d -4 d metal ions at the B -site. Substantially, it can be noticed that the interfacial charge transfer between B / B ′ site cations (Mn 3+ –O 2– –Mn 4+ to Ru 5+ –O 2– –Ru 4+ ), i.e., super exchange interactions in title DP structures, further influenced the photocatalytic water oxidation and supercapacitor activities as observed for the DP family in the previous reports. ,,,,,,,, In addition, it is known that the stoichiometry ratio modifications at the B -site in the 3 d -4 d DP system causes octahedral tilting as well as structural distortion. Such distortion in the disordered DP structure may significantly induce photochemical and electrochemical properties. ,,− ,,,,, …”

“…The Warburg finite-length diffusion at low frequency provides inputs about ion diffusion within the electrode, and the Warburg resistance ( Z W ) slope gradually changes from 45° to 90°. − ,− , At very high frequencies, the intercept of the impedance spectrum at Z′ axis denotes the internal or series resistance ( R s ), which collectively represents the intrinsic resistance of the active substrate on the electrode, the contact resistance at the interface of the active material/current collector, as well as the ionic resistance of the electrolyte used. The semicircle in the low-frequency range corresponds to the Faradic charge-transfer resistance ( R ct ) caused by the pseudo-capacitance (Faradaic reactions) at the electrode–electrolyte interface and the EDLC which is clearly visible in the CMRO-2 compound. − ,− ,− , The linear portion of the spectrum represents the Warburg resistance, and the angle made with the y -axis indicates the diffusion resistance that is offered by the electrode material to the redox element from the electrolyte. ,,,,, At lower frequency, the vertical line in the Nyquist plots of CMRO-2 in both 0.5 M H 3 PO 4 and 0.5 M H 2 SO 4 is more inclined toward…”

“…On the other hand, extensive studies on complex oxides demonstrate that double perovskites (DPs) holding the chemical formula of A 2 BB ′O 6 (where in A- site represents rare earth or alkaline-earth metal and B and B ′ stands for various transition metal cations) are highly exciting because of their facile synthesis procedure, compositional flexibility and stability, tunable electronic structures, and exceptional physicochemical properties. − Substantially, various electronic configurations, mixed-valence state, and exchange interaction of B and B ′ cations in DP structures possess a wide range of structural modifications which further lead to numerous potential applications in the area of magnetism, conductivity, electro and photocatalyses, supercapacitors, and so on. − Subsequently, it can be noted that the A -site substitution in DP structures can exhibit peculiar structure–property relationships, while B -site substitution often leads to unexpected energy conversion and storage behaviors. − Over the years, many studies focused on the progress of 3 d -3 d or 3 d -5 d metal ions combined DP structures for observing long-range magnetic and spintronics behaviors. − ,− ,− Besides, it can be noted that many DPs suffer from low electrical conductivity; hence, capacitance behaviors of such oxides appeared very low. Therefore, to increase the capacitance behaviors, combination with rGO and DPs as a composite can be a straightforward step to not only obtain a high capacitance value but also enhance the overall energy conversion and storage behaviors.…”

“…Therefore, to increase the capacitance behaviors, combination with rGO and DPs as a composite can be a straightforward step to not only obtain a high capacitance value but also enhance the overall energy conversion and storage behaviors. However, 3 d -4 d- based DP structures and their energy-related applications have been less studied, though few of them such as AA ′ B RuO 6 (where A and A ′ = Ca, Sr, and La and B = Fe and Sc) have been examined recently as promising candidates for electro and photocatalysts for water splitting. − Unfortunately, exploration of the energy-storage behaviors in 3 d -4 d- based DP systems is still an unexplored area till date.…”