Copper-incorporated hierarchical wire-on-sheet α-Ni(OH)₂ nanoarrays as robust trifunctional catalysts for synergistic hydrogen generation and urea oxidation

Abstract

Copper-incorporated α-Ni(OH)2 nanoarrays with a unique hierarchical wire-on-sheet structure and local Ni3+ species are explored as efficient trifunctional electrocatalysts for urea oxidation and water electrolysis.

A Lattice‐Oxygen‐Involved Reaction Pathway to Boost Urea Oxidation

“…The typical reaction pathway was proposed as: *CO(NH 2 ) 2 → *CO(NH.NH 2 )→ *CO(NH.NH)→ *CO(NH.N)→ *CO(N 2 )→ *CO(OH)→ *CO(OH.OH)→ *COO, with the desorption of *COO intermediate as the rate‐determining step (RDS) . Various approaches including surface engineering, structural distortion, and element doping were explored to modulate the electronic structures of Ni 3+ active sites and enhance their density in catalysts for better urea electrolysis. Unfortunately, these UOR catalysts still exhibit unsatisfactory catalytic activity, owing to the unfavorably strong binding of Ni 3+ active sites with *COO intermediate.…”

Preferential Microstructure Design of Two‐Dimensional Electrocatalysts for Boosted Oxygen Evolution Reaction

“…As demonstrated before, the basal surfaces of the 2D van der Waals crystals are less electroactive than the edges, while unfortunately, most of the exposed facets are the basal surfaces, thereby becoming the main hindrance to further improving the OER activity. Aimed on solving this problem, our group recently discovered a one‐step route to synthesize the 1D‐2D‐3D hierarchical nanoarrays based on α‐Ni(OH) 2 wire‐on‐sheet nanosheets (Figure ) . Different from β‐Ni(OH) 2 , the α‐Ni(OH) 2 possesses a typical intercalated layered structure, among the independent layers are the intercalated water molecules or anions.…”

“…Detailed structural analyses indicate that the wire‐on‐sheet nanostructure is single‐crystalline with abundant surface nanowires on the ultrathin 2D layer. Besides, by modifying the metal precursors, controllable elemental doping can be readily achieved, and the as‐obtained Cu, Fe and Ce doped catalysts exhibit remarkable performance on electro‐oxidation reactions such as OER and the urea oxidation reaction . Similarly, 2D nanosheets grown on 1D nanoarrays were also reported, for which the 1D charge transport pathway and the highly exposed surface sites could effectively boost the OER process .…”

Nickel Ferrocyanide as High-Performance Next Generation Electrocatalyst for Urea Oxidation

“…2,15 Even though a wide variety of catalysts have been developed with different compositions and structures, most of them involve NiOOH species, which limits their activity (the best one is ~101 mA cm -2 at a potential of 1.40 V vs RHE in 1.0 M KOH with 0.33 M urea). 9,16,17 Note that as a 6etransfer reaction, the UOR process should have more alternatives with optimal thermodynamics or kinetics beyond the mechanism involving NiOOH species. This has been widely validated for other multiple-electron transfer reactions such as oxygen reduction reaction and carbon dioxide reduction reaction that have multiple reaction pathways.…”