Development of clean and sustainable renewable energy sources is imperative to deal with the future energy crises. Various technologies have been developed in this context, for example, water electrolysis, reversible fuel cell and metal‐air batteries etc. However, the sluggish kinetics of oxygen evolution reaction (OER) occurring at the anode of these energy storage/conversion systems becomes a significant hurdle. Recently, researchers utilized noble metals as electrocatalysts to enhance their efficiency still the high cost and scarcity of these materials draw the attention of researchers towards the cost‐effective Perovskite oxide nanomaterials due to their extraordinary flexibility. In this review, the importance of perovskite oxide nanomaterials as electrocatalysts for OER is discussed, followed by related reaction mechanisms and series of activity descriptors. Fundamental understanding about the instrumentation, parameters and protocols for the experimental measurements including concerned issues are also summarized. Moreover, various activation strategies adopted in recent years to enhance the electrocatalytic performance of perovskite oxides are also underlined. The article concludes with an outlook of existing challenges and future scope of these materials as electrocatalysts. The challenges and prospects discussed herein may pave the ways to rationally design the highly active and stable perovskites to outperform noble metal‐based OER electrocatalysts.

Heterostructures (HS) have always been in attraction due to their inherited properties and different important applications. Integration of a phase-change material (PCM) with HS can tremendously extend the operating and application range using the “phase-tuning” of PCM for any optoelectronic devices. In the present study, we report a detailed study of electrical and optoelectronic characteristics of a p-p and p-n HS combining Ge₂Sb₂Te₅ (GST) and Si. Reasonable 2 order of resistance switching is achieved by thermal annealing. The changes in optical properties are analysed using Ellipsometry, UV–Vis–NIR and Raman spectroscopy to speculate the optoelectronic behaviour of GST/Si samples. The optical and electrical characterization were analysed with aluminium (Al), platinum (Pt) and Ti/Au contacts. Appreciable rectifications varying from 500 to 1,000 at lower voltages are achieved with different contacts for both phases of GST. The change in rectification amount and current polarity are obtained with different kinds of contacts and at different incident wavelengths indicating different mechanisms of charge separation and collection. Responsivity of more than 9 A/W with < 1,000 photo-current to dark-current ratio is demonstrated in wavelength range of 0.8–2 μm under moderate range of biasing under ~ μW source power illumination. The characteristics obtained were justified with the prediction of band alignment with the help of work-function difference measurement by Kelvin-probe force microscopy and carrier density measurement by Hall experiment. Our results provide understanding to the opto-electrical behaviour of a heterojunction made of stacking PCM (GST) on Si highlighting their future use in photonic/optoelectronic-integrated circuits.