Applications of Nickel‐Based Electrocatalysts for Hydrogen Evolution Reaction

Abstract

The desire to exploit clean and sustainable energy sources with high gravimetric energy density has greatly inspired the exploration of hydrogen energy as an affordable alternative to fossil energy. Electrocatalytic water splitting is an efficient method for the low‐cost production of pure H2, but the use of platinum (Pt)‐like active electrocatalysts for the hydrogen evolution reaction (HER) remains necessary. In attempts to replace high‐value, scarce Pt catalysts, nickel‐based materials are being developed, as earth‐abundant HER electrocatalysts. Recently, a number of advanced nickel (Ni)‐based catalysts have been developed by rational synthesis strategies, including morphology control, structure tailoring, and interface engineering, significantly improving the HER performance. This review summarizes recent achievements in the application of Ni‐based HER electrocatalysts and demonstrates the advantages of each category in enhancing the HER performance. The current progress in the theory of water evolution and various modern techniques for characterizing catalysts are also reviewed, along with the rational design of Ni‐based nanostructure catalysts. Finally, the challenges in the practical applications of Ni‐based HER catalysts are highlighted.

Non‐Stoichiometric NiFeMo Solid Solutions; Tuning the Hydrogen Adsorption Energy via Molybdenum Incorporation

“…The NiFeMo-2* shows a good stability for at least 24 h with an increase of η 10 to 162 mV, still a competitive value for Ni-based electrocatalysts. [3,4] Besides a stainless-steel mesh, we also used Ni foam and carbon paper (CP) as a substrate during the electrocatalyst production without any alteration in the synthesis process, which highlights the versatility of the SPPS technique. The major difference when using different substrates was the increase η 10 value, to 186 and 212 mV for Ni foam and carbon paper, respectively.…”

“…In the case of nickel, the formation of alloys is a common strategy to modify both morphology and intrinsic activity, where NiCo, NiFe, and NiMo mixtures have been identified as promising HER electrocatalysts. [ 2b,4,5 ] The use of multicomponent alloys is a natural extension from binary systems, where ternary alloys such as CuAlNi, NiMoFe and NiMoW, [ 2b,4 ] have been studied, although the role of each metal is not fully understood. Out of the common Ni‐alloys, NiFe mixtures typically exhibit better catalytic performance, and in particular, the addition of Mo into these alloys have resulted in a reduced onset potential due to favorable hydrogen–metal interaction, and an increased number of active sites.…”

“…Out of the common Ni‐alloys, NiFe mixtures typically exhibit better catalytic performance, and in particular, the addition of Mo into these alloys have resulted in a reduced onset potential due to favorable hydrogen–metal interaction, and an increased number of active sites. [ 4,6 ] Hence, NiFeMo alloys are among the most promising HER electrocatalysts which are mainly produced via hydrothermal processes [ 7 ] or by electrodeposition. [ 8 ] The choice of the synthesis technique has a significant impact on the catalyst morphology, and generally a different optimal Ni:Fe:Mo metal ratio are reported.…”

“…[1,3] Since the 1960's there has been a significant effort to improve the catalytic activity of Ni-based electrocatalysts with a large variety of promising candidates such as nickel hydroxides, dichalcogenides, phosphides, carbides, and others. [1,4] Generally, the catalytic activity can be enhanced by increasing the active surface area by tuning the catalysts morphology (e.g., production of nanowires, nanosheets, nanoparticles, etc.) and improving the intrinsic activity of the available active sites (e.g., by alloying, doping, defect engineering,…”

Ultrathin NiPt Single-Atom Alloy for Synergistically Accelerating Alkaline Hydrogen Evolution

“…Hence, developing single-atom catalysts came to be considered a cost-efficient approach by maximizing the utilization efficiency of noble metals. − Besides, the HER catalytic activity of Pt is significantly lower in alkaline media compared with that in acidic media, which mainly suffers from sluggish kinetics in the Volmer step. − The Volmer step is the process where water molecules are dissociated into adsorbed hydrogen (H*) and a hydroxyl radical, which is one of the electrochemical reactions involved in alkaline HER. The other reaction is to convert H* to H 2 by combining two adsorbed hydrogen atoms (Tafel step) or by bonding one hydrogen atom and one water molecule (Heyrovsky step) . Considering the electronic interaction between the support and monoatomic Pt in the interface, rational design of a substrate is of great importance to minimize the barrier for cutting the strong OH–H bonds.…”