Heterojunction Engineering for Electrocatalytic Applications

Abstract

Production of green hydrogen from the electrolysis of water is considered to be one of the most desirable processes to address the clean energy demand. However, a high energy barrier and an economically unsustainable nature limit the process toward practical implementation in an extensive way. The designing of an electrocatalyst accompanied by defect engineering, heteroatom doping, and strain creation are known to be effective strategies to make the process efficient. Recently, construction of heterojunctions with a combination of materials with desired band structures is considered to be a smart approach in promoting electrocatalytic activities by attaining charge redistribution and manipulating the electronic structure at the interface. The present review elaborately discusses possible heterojunctions, alterations at the interface, insight thermodynamics, and possible causes for boosting electrocatalytic activities. The heterojunction-based electrocatalysts are found not only effective for oxygen evolution reactions and hydrogen evolution reactions, but also to be very useful toward various electrochemical oxidation reactions as well as electrochemical reduction reactions involving small molecules undergoing decomposition at very low energy. Having such a specialty, there is no doubt that heterojunction-based electrocatalysts are going to be the primary choices of researchers in coming years.

Unveiling The Multifunction of Beaded Stream‐Like Co9Se8 Catalysts for Water Splitting, Reactive Oxygen Species Scavenging, and Hydrogen Anti‐Inflammation

“…This interface provides favorable sites for the absorption of reaction intermediates, enabling a more efficient OER. [ 39 ] For comparison, devices with Pt−C/Ti and RuO 2 /Ti electrodes were assembled as benchmarks. In Figure 4b, the polarization curves indicate a water‐splitting voltage of 1.44 V for the Co(OH) 2 −Co 9 Se 8 /Ti//Co 9 Se 8 /Ti configuration, achieving a current density of 10 mA cm −2 .…”

High-Entropy Borate as an Active Electrocatalyst for Boosted Alkaline Seawater Oxidation

“…However, the process is critical and includes two key reactions: the hydrogen evolution reaction (HER) occurring at the cathode and the oxygen evolution reaction (OER) at the anode, which often limit the overall process due to its sluggish kinetics. The search for electroactive catalysts, especially for the OER mechanism (4OH – = 2H 2 O + O 2 + 4e – , E a 0 = +0.4 V), other than noble-metal-based electrocatalysts, like IrO 2 and RuO 2 , has thereby been continued by researchers. − Apart from electrocatalyst designing, the large consumption of freshwater for hydrogen production is another concerning factor, which in principle can be addressed by using seawater due to its abundance . However, the presence of chlorides, especially along with other minerals, often makes the process infeasible due to severe corrosion at the anode caused by the interfering chlorine evolution reaction (CER). − The Pourbaix diagram of 0.5 M aqueous NaCl solution suggests 480 mV as the limiting overpotential in alkaline conditions, beyond which CER dominates.…”

“…Often, transition-metal-based oxides or nonoxides have been extensively explored as electrocatalysts. − However, the instability of the material or alteration in the surface composition in harsh electrolytes causes deterioration in their electrocatalytic performances. The development of high-entropy alloys composed of five or more metal elements, with the atomic percentage of the elements being within 5–35%, has been the new interest in this field due to the availability of large numbers of active sites along with great stability. − However, developing a single-phase complex solid solution composition consisting of five or more metal elements is considerably intricate and requires rational synthesis techniques.…”