Enhanced Urea Activity of Oxidation on Nickel‐Deposited Tin Dendrites

Abstract

Urea oxidation has gained tremendous research interest, owing to its application in direct urea fuel cells and urea electrolyzers. In this work, the electrochemical oxidation of urea on a Ni/Sn dendrites catalyst is investigated. Ni and Ni/Sn dendrites are synthesized through electrodeposition on porous Toray © carbon paper. The prepared catalysts were characterized by scanning electron microscopy, X-ray diffraction, and inductively coupled plasmaÀoptical emission spectroscopy. The Ni/Sn dendrites oxidized 0.33 M urea in alkaline solution at an onset potential of 0.34 V vs. Ag/AgCl with a current density of 44 mA cm À2 @0.55 V, which is higher than that of electrodeposited Ni/TC (31 mA cm À2 @0.55 V). In situ Raman spectroscopic measurements indicate that urea oxidation on Ni/Sn dendrites is initiated by Ni(III)OOH species. Electrochemical impedance spectroscopy patterns of Ni/Sn dendrites in the presence of urea displayed a single depressed semicircle at potentials of 325 mV and two semicircles above 325 mV with a decreased total charge-transfer resistance. The Ni/Sn dendrites electrode shows lower resistance at the tested potentials, indicative of faster urea oxidation kinetics.

Electroactivity of NiCr Catalysts for Urea Oxidation in Alkaline Electrolyte

“…A significantly low onset potential of 0.32 V is observed with 40 % Cr in NiCr catalysts (Figure (b)). This value is among the lowest reported compared with 0.29 V, 0.34 V, and 0.35 V under similar conditions. Figure (c) displays the current densities at selected potentials of 0.40, 0.45, 0.50, and 0.55 V as a function of atomic Cr %, which shows a volcano‐shape behavior.…”

“…Thereafter, the NiOOH intermediate was probed by in situ surface‐enhanced Raman spectroscopy and in situ X‐ray diffraction (XRD) . To further improve urea oxidation on Ni catalysts, a variety of binary and ternary Ni‐based catalysts, such as Ni–Rh, Ni–Co, Ni–Zn–Co, Ni/WC, and Ni/Sn were reported. Most of the catalysts used for urea oxidation were prepared by an electrodeposition method, with which the yield is limited .…”

An Insight on the Electrocatalytic Mechanistic Study of Pristine Ni MOF (BTC) in Alkaline Medium for Enhanced OER and UOR

“…The increment in the catalytic activity with decreasing h is due to increase in catalytic active sites under the electrochemical ageing, formation of more active and electrical conductive NiOOH intermediates, adsorption/desorption and diffusion of OH À ions and O 2 and structural rigidity of MOF. [78][79][80][81][82] Figure S14 in ESI and Figure 10 shows the survey and deconvoluted XPS spectrum of respectively Ni 2p, O 1s and C 1s of Ni MOF with Nafion binder on the CP substrate before and after OER reaction at a current density of 10 mA cm À2 for 10 hours. Figure 9 and Figure S13 in ESI shows the optical and SEM image of Ni MOF before and after chronopotentiometry studies.…”

Nanostructured Ni2P‐C as an Efficient Catalyst for Urea Electrooxidation

“…Catalyst materials based on Ni for urea electrolysis were firstly reported by G.G.Botte et al in alkaline solution and then nickel as a non‐precious metal was found to have a good performance for urea oxidation . In order to further improve urea oxidation kinetics, the nickel alloy catalyst material was proposed such as Ni−Co, Ni−Zn‐Co, Ni/WC, Ni−Rh and Ni/Sn etc. Meanwhile, noble metals catalyst based on Pt such as Pt−Ir‐Ni was also prepared as catalyst for urea electro‐oxidation in alkaline solution.…”