Recent advances in perovskites for electrocatalytic and photocatalytic water splitting processes: Materials, characterizations, synthesis and applications

Abstract

Perovskites have attracted attention for hydrogen production due to their structural flexibility, high efficiency, high stability, low cost, tunable bandgap, good thermal stability, high electron transfer. This review describes the recent progress made in the field of perovskites, which includes their characterizations, synthesis and applications on the electrocatalytic and photocatalytic water splitting processes. The improvement of stable, low cost, efficient, earth abundant and active electrocatalysts is crucial for the hydrogen production. Especially, perovskite oxides are preferable for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) due to their perfect catalytic ability, diversity in the formation of abundant oxygen vacancies and good electronic conductivity. Perovskite oxides provide to accelerate charge transfer , ease the formation of oxygen vacancy, tends to change oxidation state and increase electrocatalytic activity. Some methods such as doping and coupling with metal, non-metal and cocatalyst are applied to improve their performances. This review underlines the effect of doping on perovskite oxides in OER and HER mechanisms and the improvement of bifunctional perovskite oxides. The effect of anion and cation doping are investigated because doping enhance surface properties and electronic structures of catalysts by improving intrinsic catalytic activity. A-site doping influences both OER and HER performances by activating B-site. B-site doping is more effective method for designing effective perovskite oxides in terms of stability, activity and performance. Especially Fe doping is preferable at B-site due to its high valence to improve OER performance. O-site doping affects crystal structure, electronic structure, ionic conductivity, chemical stability, band structure, charge balance, concentration of oxygen vacancy and oxygen ion mobility. Dual doping (A,B-site and B,O-site) also provides the formation of multi active sites especially for HER. Generally, high entropy perovskite oxides possess small overpotential and Tafel slope with faster reaction kinetics due to their high covalency. There is a growing interest in developing bifunctional electrocatalysts, which can catalyze both the HER and OER. The development of an ideal bifunctional electrocatalyst are also crucial because they have high stability and high activities to provide long-term stability for both HER and OER mechanisms.

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