Nanostructured Intermetallic Nickel Silicide (Pre)Catalyst for Anodic Oxygen Evolution Reaction and Selective Dehydrogenation of Primary Amines

Abstract

Water electrolysis consists of two electrochemical half-reactions: the hydrogen evolution reaction (HER) to produce hydrogen at the cathode and the OER to evolve oxygen at the anode, respectively. While the HER is a relatively straightforward two-electron transfer process, the main bottleneck is the sluggish four-electron OER that limits the overall efficiency of water electrolysis. [2,3] Currently, the common and matured industrialized electrolyzers to produce hydrogen rely on either acidic (proton-exchange membrane) or alkaline conditions. Out of which, alkaline electrolyzers are of particular importance as they use low-cost and earth-abundant materials to make the system fully sustainable and economically competitive. [4] As stated above, in order to increase the efficiency of the electrolyzers, improved anodes with high intrinsic activity are required. Notably, for alkaline electrolyzers, Ni-based materials have been the typical choice as anode (OER) materials because of their cost-effectiveness, high elemental abundance, good resistance to corrosive solutions, and low toxicity. [5,6] In recent years, significant progress has been achieved in the design, synthesis, and development of a variety of highly efficient Ni-based electrocatalysts involving oxides/hydroxides, chalcogenides, pnictides, alloys, and even metal-organic frameworks for OER at the lab scale to minimize the energetic losses in alkaline electrolysis. [6][7][8][9][10][11] Besides, significant efforts have been made to modify Ni-based electrocatalysts through heterostructure formation, oxygendefect generation, doping with heteroatoms, as well as phase and morphology engineering to attain technically viable efficiencies. However, further improvement beyond the current state of the art is required to enhance the overall OER performance. [9][10][11][12][13][14] Most of the Ni-based catalysts transform under the electrochemical alkaline conditions into electronically similar layered oxyhydroxide (LOH) phase with Ni III O x H y structure. [15,16] Similar to other transition-metal electrocatalysts, the OER activity of Ni-based catalysts largely depends on the defects, surface area, morphology, crystal structure of the precatalyst (e.g., NiNi distances), amount of edge/corner-sharing [NiO 6 ] units, size of the crystallite domain, etc. of the transformed Ni III O x H y phases,The development of novel earth-abundant metal-based catalysts to accelerate the sluggish oxygen evolution reaction (OER) is crucial for the process of large-scale production of green hydrogen. To solve this bottleneck, herein, a simple one-pot colloidal approach is reported to yield crystalline intermetallic nickel silicide (Ni 2 Si), which results in a promising precatalyst for anodic OER. Subsequently, an anodic-coupled electrosynthesis for the selective oxidation of organic amines (as sacrificial proton donating agents) to value-added organocyanides is established to boost the cathodic reaction. A partial transformation of the Ni 2 Si intermetallic precatalyst generates a poro...

Upgrading Organic Compounds through the Coupling of Electrooxidation with Hydrogen Evolution

“…In a hybrid electrolyzer, propionitrile and H 2 were produced on the anode and cathode, respectively. Similar approaches were also reported by the groups of Huang, Yan, Mondal, and Xiong for amine upgrading and H 2 generation [85–88] …”

“…Similar approaches were also reported by the groups of Huang, Yan, Mondal, and Xiong for amine upgrading and H 2 generation. [ 85 , 86 , 87 , 88 ]…”

Reviving Oxygen Evolution Electrocatalysis of Bulk La–Ni Intermetallics via Gaseous Hydrogen Engineering

“…[ 15,46 ] The intensity ratio of E g to A 1g peak was ≈1.37, implying the presence of lattice defects in the γ‐NiOOH phase. [ 45,46 ] Meanwhile, the characteristic signals (A g and E 2g translatory modes at ≈281 and 336 cm −1 , respectively) belonging to La(OH) 3 could also be identified for LaNi 5 ‐H‐100th during alkaline OER. [ 47,48 ] On the other hand, the in situ Raman spectra during the OER process were also carried out for LaNi 5 ‐F, and the results suggested a similar phase evolution to that of LaNi 5 ‐H‐100th/FTO (Figure S16, Supporting Information), that is, the generation of La(OH) 3 and γ‐NiOOH on the surface.…”

Aufwertung organischer Verbindungen durch Kopplung von Elektrooxidation und Wasserstoffentwicklung

“…[83] Verschiedene aromatische ( [84] In einem Hybridelektrolyseur wurde an der Anode Propionitril und an der Kathode H 2 erzeugt. Von ähnlichen Ansätzen zur Aminaufwertung und H 2 -Erzeugung berichteten auch Huang, Yan, Mondal und Xiong et al [85][86][87][88]…”