Transition Metal Non‐Oxides as Electrocatalysts: Advantages and Challenges

Abstract

energy crisis. To satisfy this surging global energy demand, people often tend to use nonrenewable resources (coal, petroleum, natural gas, etc.), which generates an enormous amount of greenhouse gases, causing great obstacles for the development of a healthy human society. [1] To avoid such unhealthy environmental pollution, the use of renewable energy resources such as wind, solar, hydroelectric power, etc., over the past few years has served as the top priority to meet the global energy demand. The advancement of science and technology and the global realization of escalating energy demand have led the present generation to explore clean energy sources as future alternatives due to their easy accessibility and high energy density. [2,3] Consequently, in recent years, energy conversion technologies focusing on the conversion of renewable energies (wind, water, etc.) into easily stored chemical energy is attracting much attention. [4][5][6] The electrochemical splitting of water molecules to generate highly efficient hydrogen and oxygen is considered to be one of the promising methods for the generation of green hydrogen as a clean fuel alternative to fossil fuel. [7][8][9][10][11] Hydrogen, present in abundance, with zero carbon emissions and high energy yield, is considered an efficient energy carrier similar to electricity and batteries. The electrocatalytic process in an electrolyzer involves hydrogen generation at the cathode based on the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at the anode. [12,13] However, in practical applications, the largescale utilization of water electrolysis is seriously hindered due to the sluggish kinetics of OER and lack of stability of the electrocatalyst. [14] The sluggish reaction kinetics of OER are due to the four-electron transfer reaction, which requires overcoming a considerable amount of activation energy barrier corresponding to the breaking of the O-H bond and the formation of the O-O double bond, unlike HER, involving only two electron-transfer reactions. On the other hand, the oxygen reduction reaction (ORR), as a very important part of fuel cell applications, also requires four electron transfer pathways to dissociate the O-O double bond with slow reaction kinetics. To overcome the sluggish kinetics of OER, diverse studies have been devoted to designing electrocatalysts to facilitate the process. Undoubtedly, noble metal (Ru, Ir)-based electrocatalysts well served in minimizing the required activation energy, The identification of hydrogen as green fuel in the near future has stirred global realization toward a sustainable outlook and thus boosted extensive research in the field of water electrolysis focusing on the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). A huge class of compounds consisting of transition metalbased nitrides, carbides, chalcogenides, phosphides, and borides, which can be collectively termed transition metal non-oxides (TMNOs), has emerged recently as an ef...

Interfacial engineering and chemical reconstruction of Mo/Mo2C@CoO@NC heterostructure for promoting oxygen evolution reaction

“…Transition metal carbides (TMCs), such as Mo 2 C, W 2 C, TiC, NbC, and VC, have broad application prospects in the field of energy storage and conversion due to their good thermal stability, mechanical properties, and high electrical conductivity. 16 Mo 2 C, in particular, has become a research focus due to its low cost and high hydrogen production efficiency. 17 However, producing well-defined nanostructures with a high density of catalytically active sites remains a challenge.…”

Nickel–Vanadium–Manganese Trimetallic Nitride as Energy Saving, Efficient Bifunctional Electrocatalyst for Alkaline Water Splitting via Urea Electrocatalysis

“…The initial Volmer step involves the formation of M−H bond by decomposition of H 2 O in the alkaline medium followed by adsorbing hydrogen from the electrolyte in the second step liberating H 2 gas. 12 The small intrinsic series resistance (R s ) value of 0.89 Ω reflects the best electrical conductivity of the material, and also the small R ct value of 1.1 Ω indicates smaller chargetransfer resistance (Figure 5c). Moreover, the long-term chronoamperometry study of N10V7M3 achieving cathodic current density of around 10 mA cm −2 by applying −1.15 V over 24 h shows good retention indicating outstanding stability of the catalyst (Figure 5d).…”

“…In this regard, transition-metal nonoxides, especially transition-metal nitrides (TMNs), have attracted much attention because of their special characteristics, like outstanding electronic properties, electrical conductivity, corrosion resistance nature, and high chemical stability. 12 TMNs, for example, Ni 3 N, Co x N, and Fe x N, are often found to be much suitable toward HER mechanism. 13−16 Among these, Ni 3 N has shown much potential to be considered for both HER as well as UOR.…”

Rational Design for Efficient Bifunctional Oxygen Electrocatalysts by Artificial Intelligence

“…15 Moreover, transition metal carbides, nitrides, selenides, and chalcogenides have also been used for OER and ORR electrocatalysis. 12,15,16 For example, Wei et al reported a composite electrocatalyst-integrated N-doped graphene and Co/Fe oxides, achieving an excellent performance with an ΔE of 0.78 V. 17 solution for efficient ORR/OER activity. Artificial intelligence (AI) and machine learning (ML) have brought brilliant solutions to this problem, which reveal patterns in training data using statistical models and optimization algorithms to make predictions or decisions.…”

“…The composite of carbon materials with transition metal oxides/hydroxides and heteroatom doping have been reported as bifunctional materials for OER/ORR in the alkaline electrolyte . Moreover, transition metal carbides, nitrides, selenides, and chalcogenides have also been used for OER and ORR electrocatalysis. ,, For example, Wei et al reported a composite electrocatalyst-integrated N-doped graphene and Co/Fe oxides, achieving an excellent performance with an Δ E of 0.78 V . Deng et al presented a single-atom catalyst of N-doped carbon with embedded Co/Ni, which delivered a superior bifunctional ORR/OER activity (Δ E = 0.81 V) .…”