Noble-Metal-Free Bifunctional Electrocatalysts for Overall Water Splitting in Alkaline Medium

The ever-growing energy crisisEnergy crisis and environmental pollutionEnvironmental pollution motivated scientific researchers to develop a green energyEnergy economy. Hydrogen generationHydrogen generation through electrochemical water splittingWater splitting has shown immense potentiality to be an important energy conversionEnergy conversion technology towards the said goal. The electrochemical water splittingWater splitting consists of two half-cell reactionsHalf-cell reactions: hydrogen evolutionHydrogen evolution reactionReaction (HER) and oxygen evolution reaction (OER)Oxygen Evolution Reaction (OER). The overall water splittingWater splitting is sluggish as both of these half-cell reactionsHalf-cell reactions involve multiple protonProton and electron transferElectron transfer steps. Theoretical as well as experimental results have revealed that the noble-metal-based electrocatalystsNoble-metal-based electrocatalysts (such as Pt and RuO2RuO) possess superior electrocatalytic activityElectrocatalytic activity toward water splittingWater splitting. However, these materials lack commercial-scale applicability due to their high price and lower abundanceAbundance. Recently, numerous investigations have been conducted to develop cheap and efficient noble-metal-freeNoble-metal-free electrocatalystsElectrocatalyst. Pure waterWater is a poor conductor of electricityElectricity and thus an electrolyteElectrolyte is added to facilitate the overall water-splittingWater splitting process. The efficiencyEfficiency and costCost-effectiveness of water electrolysisWater electrolysis are higher in an alkaline mediumAlkaline medium if all the technical aspects related to it are considered together. An electrocatalyst with sufficient bifunctional activityBifunctional activity towards both HERHydrogen Evolution Reaction (HER) and OEROxygen Evolution Reaction (OER) in the same operational condition simplifies the electrolyzerElectrolyzer optimization process and consequently, higher efficiencyEfficiency in full water splittingWater splitting is achieved. So, a cheap and efficient bifunctional noble-metal-freeNoble-metal-free electrocatalystElectrocatalyst for water splittingWater splitting in an alkaline mediumAlkaline medium is highly desirable. BoridesBoride, carbidesCarbide, pnictidesPnictides, and chalcogenidesChalcogenide of transition metalsTransition metal like Fe, Co, Ni, etc. show significant promise in that context. Few transition metalTransition metal-based heterostructuresHeterostructure and engineered electrocatalysts also exhibit desirable bifunctional activityBifunctional activity towards overall water splittingWater splitting. This chapter provides a brief idea about electrocatalytic water splittingWater splitting and also summarizes some recent advancements in noble-metal-freeNoble-metal-free bifunctional electrocatalystBifunctional electrocatalyst development. Finally, the future prospects in the development of efficient and cheap bifunctional electrocatalystsElectrocatalyst for water splittingWater splitting have been discussed.