Earth‐Abundant Transition‐Metal‐Based Bifunctional Electrocatalysts for Overall Water Splitting in Alkaline Media

Abstract

The depletion of fossil fuels has accelerated the search for clean, sustainable,s calable, and environmentally friendly alternative energy sources. Hydrogen is ap otential energy carrier because of its advantageous properties, and the electrolysis of water is considered as an efficient method for its industrial production.H owever,t he high-energy conversion efficiency of electrochemical water splitting requires cost-effective and highly active electrocatalysts. Therefore, researchers have aimed to develop high-performance electrode materials based on non-preciousa nd abundant transition metalsf or conversion devices. Moreover,t of urther reduce the cost and complexityi nr eal-worlda pplications, bifunctional catalysts that can be simultaneously active on both the anodic (i.e.,o xygen evolutionr eaction, OER) and cathodic (i.e.,h ydrogen evolution reaction,H ER) sides are economically and technically desirable. This Minireview focuses on the recent progress in transition-metal-based materials as bifunctional electrocatalysts, includings everalp romising strategies to promote electrocatalytic activitiesf or overall water splitting in alkaline media, such as chemical doping, defect( vacancy) engineering, phase engineering, facet engineering, and structure engineering.F inally,t he potential for further developments in rational electrode materials design is also discussed. He received his Ph.D.f rom the Universityo f Mississippi, Oxford (MS), USA, in 1997. His researchg roup focuses on several main topics, such as organic synthesis, wet chemicals ynthesiso fn anomaterials (graphene, transitionmetalc halcogenides( TMDs), blue TiO 2 ,e tc.). He and his group have published many highquality peer-reviewed-papers,w hich earned him over 12 000 citations with an H-index of 50 and an i10-index of 123 so far.Scheme1.Strategiestoi mprovee lectrocatalytic activity of earth-abundant transition-metal-based electrocatalysts.

Electronic modulation and interface engineering of electrospun nanomaterials‐based electrocatalysts toward water splitting

“…Vacancy modulation is another efficient route to tailor the neighboring atomic arrangement and surface electronic structure of the electrocatalysts, which is beneficial for the improvement of the electrocatalytic activity for water splitting 51,52 . First, vacancy is able to increase the number of exposed electrocatalytic active sites.…”

“…Vacancy modulation is another efficient route to tailor the neighboring atomic arrangement and surface electronic structure of the electrocatalysts, which is beneficial for the improvement of the electrocatalytic activity for water splitting. 51,52 First, vacancy is able to increase the number of exposed electrocatalytic active sites. Second, the electrical conductivity of the catalyst can be improved resulting from the new gap generation within its bandgap, benefiting for the efficient charge transfer.…”

Understanding Surface Modulation to Improve the Photo/Electrocatalysts for Water Oxidation/Reduction

“…Electrocatalytic reactions typically involve multiple, successive steps occurring on the interface of a solid electrocatalyst and the electrolytes [108][109][110][111][112][113]. It is generally known that the adsorption of reactants is considered the initial step, followed by the reaction, and finally desorption for any kind of heterogeneous catalytic processes.…”

Quasi‐Parallel NiFe Layered Double Hydroxide Nanosheet Arrays for Large‐Current‐Density Oxygen Evolution Electrocatalysis

“…Designing highly efficient catalysts for oxygen evolution reaction (OER) is essential for the development of water splitting devices and rechargeable metal‐air batteries [1] . Iron‐group compounds including iron, cobalt, and nickel have been considered as promising candidates as oxygen‐evolving electrocatalysts because of their low cost, abundance in nature, and special redox characteristics [2–4] . Among them, NiFe layered double hydroxide (NiFe LDH), a mineral‐like compound containing the layers of Ni(OH) 6 shared‐edge octahedra with some Fe 3+ atoms occupying Ni 2+ sites, has been demonstrated to display electrocatalytic signatures [5–7] .…”