NiSe@NiOx core-shell nanowires as a non-precious electrocatalyst for upgrading 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid

Hollow NiSe Nanocrystals Heterogenized with Carbon Nanotubes for Efficient Electrocatalytic Methanol Upgrading to Boost Hydrogen Co‐Production

“…[ 5,12,25,29 ] In previous studies for Ni‐based anodic electrocatalysts, the higher oxidation state of transition metal (e.g., Ni 3+ ) as well as the NiOOH species are considered as critical active sites for electro‐oxidation reaction (e.g., OER). [ 28,29,57 ] Nevertheless, the MUR on h‐NiSe/CNTs/CC is preferable at lower potential than full water electrolysis. Besides, the catalytic current obtained at the potential greater than 1.47 V (vs RHE) is accompanied by observable O 2 production for OER.…”

“…Compared with the fresh h‐NiSe/CNTs‐f in Figure a, the h‐NiSe/CNTs‐s shows an obvious decrease of the XPS peak at ≈853 eV belonging to metallic Ni. [ 5,10,14 ] The h‐NiSe/CNTs‐o exhibits new emerged XPS peaks (Figure 3a) at 857.2 and 875.0 eV, respectively for Ni 2p 3/2 and Ni 2p 1/2 , suggesting the partial formation of higher valent Ni 3+ after 20 hours’ methanol conversion, [ 29,49,57 ] accompanied with the disappearance of the peak for metallic Ni. The phenomenon of gradual hydroxylation/oxidation is also demonstrated by the appearance of O 2− species (lattice oxygen, Figure 3b) at 530.1 eV in h‐NiSe/CNTs‐s and highly increased intensity of O 2− peak in h‐NiSe/CNTs‐o.…”

“…On the other hand, organic selective oxidation substituting for OER at high current density is of great significance to the high production efficiency of both value‐added chemicals and H 2 in large‐scale application. Nevertheless, organic upgrading reactions with high selectivity are usually conducted at low current densities, [ 25–29 ] although high current density is easily achieved in OER or sacrificial oxidation reactions using metal chalcogenide electrocatalysts. [ 10,30,31 ] One possible concern is that the electro‐oxidation at high current density (>100 mA cm −2 ) may be risky to excessively oxidize the organic molecules to CO 2 greenhouse gas and lose their economic values.…”

2,5-Furandicarboxylic acid production via catalytic oxidation of 5-hydroxymethylfurfural: Catalysts, processes and reaction mechanism

“…Driven by the electrochemical potential, more and more innovative and cheap catalysts developed from earth-abundant transition metals, such as Ni 2 P [133], CoP [134], Ni 2 S 3 [135], porous Ni [136], Ni x B [137], CoB [138], NiB x [139], NiCo 2 O 4 [140,141], VN [142], Ni 3 N@C [143], Ni/Co/Fe oxyhydroxides [144], Ni/NiOOH [145], nanocrystalline Cu foam [146], CuNi(OH) 2 /C [147], NiSe@NiO x [148], NiFe-LDH [127], and Cu x S@NiCo-LDH [149], were reported to be more efficient than noble metal catalysts, reversing the situation that the precious metal catalysts are more active and popular than the transition metal catalysts in HMF thermocatalytic oxidation. Grabowski et al [132] firstly reported the HMF electrooxidation into FDCA on NiOOH anode, realizing 71% FDCA yield with 84% faradaic efficiency (FE) in a divided H-shape electrolyzer with 1 M NaOH aqueous electrolyte.…”

“…After adding HMF to reach 100 mM, the required potential at the benchmark 10 mA cm À2 current density was just 1.269 V vs RHE with the corresponding Tafel plots of 125 mV dec -1 , demonstrating the highly thermodynamic and kinetic activities of the as-synthesized CoNW/NF catalyst. To our best knowledge, the result is still superior to the vast majority of the reported catalysts for electrooxidation of HMF, such as Ni 2 P NPA/NF (1.35 V vs RHE at onset) [133], Ni 3 S 2 /NF (1.35 V vs RHE at onset) [135], Co-P/CF (1.30 V vs RHE at onset) [134], hp-Ni (~1.35 V vs RHE at onset) [136], Ni x B/NF (1.38 V vs RHE at onset) [137], Nano-Cu foam (1.25 V vs RHE at onset) [146], NiCo 2 O 4 /NF (~1.36 V vs RHE for 10 mA cm À2 ) [140], NiFe LDH (1.25 V vs RHE at onset) [127], CuNi(OH) 2 /C (1.45 V vs RHE for 9.2 mA cm À2 ) [147], NiSe@NiO x (1.35 V vs RHE at onset) [148], and MoO 2 -FeP@C (1.323 V vs RHE at onset) [154]. For HER, the cathodic LSV curves exhibited no visible difference with and without HMF participation even the concentration of HMF up to 100 mM, contrasted to the situation of NF with 14 mV negative shift when 100 mM presented, indicating CoNW catalystequipped with a high preference for hydrogen formation rather than the possible reduction of aldehyde groups of HMF and intermediates.…”