Solvent modulated self‐assembled VS ₂ layered microstructure for electrocatalytic water and urea decomposition

Abstract

Summary Urea oxidation reaction (UOR) assisted water‐splitting is a promising approach for effective treatment of urea‐rich waste‐water at the anode and parallelly generate green‐hydrogen (H2) energy at the cathode via hydrogen evolution reaction (HER). However, facile designing and fabricating robust and cheap electrodes derived from earth‐abundant materials is a great challenge. This work reports the synthesis of vanadium sulfide (VS2) micro‐flowered structure via solvent‐assisted hydrothermal method using ethylene glycol as an additive in the aqueous‐based reaction medium, which has imparted a significant effect on the morphology and the crystallinity of the VS2. In addition, in contrast to the VS2 electrode fabricated in a pure aqueous medium, the ethylene glycol mediated VS2 electrode upon coupling as a cathode and anode in an HER||UOR vs reversible hydrogen electrode (RHE)‐based three‐electrode configuration demonstrates a significantly reduced overall urea decomposition potential of 1.38 V at a current density of 10 mA cm−2 as compared to the conventional water‐splitting of 1.75 V vs RHE. The obtained high‐performance electrocatalytic activity on UOR and HER can be ascribed to the influence of ethylene glycol solvent, particularly on VS2 growth, morphology, and crystallinity, favoring the formation of abundant catalytic sites with facile electrolyte diffusion and electrolysis.

rGO functionalized (Ni,Fe)-OH for an efficient trifunctional catalyst in low-cost hydrogen generation via urea decomposition as a proxy anodic reaction

“…Although the (Ni,Fe)-OH@rGO/NF electrode demonstrates a superior OER performance, its overpotential can be further improved by other oxidation reactions such as hydrazine oxidation 52,53 and urea oxidation, [26][27][28]43,54 which can achieve the anodic reaction at a lower overpotential than the OER, leading to a low hydrogen production cost. In particular, urea can be oxidized thermodynamically at 0.37 V vs. RHE while the water molecules require a higher potential of 1.23 V vs. RHE, suggesting that urea is decomposed prior to water at 0.86 V. This advocates that the UOR is a promising proxy anodic reaction to replace the conventional OER for the efficient generation of hydrogen at the cathode.…”

“…This can be achieved by developing electrocatalysts derived particularly from the earth-abundant materials that work for both cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER) with high catalytic activity and durability under operational conditions in harsh alkaline (pH ∼ 14) or acidic ( pH ∼ 0) electrolytes. A diverse variety of HER and OER catalysts derived from earth-abundant metalbased materials, such as oxide/hydroxide, [19][20][21][22][23][24] sulfide, [25][26][27][28][29][30] telluride, [31][32][33] selenide, 34,35 phosphide, 36 carbide, 37 nitride, 38 and metal-organic frameworks [39][40][41] have been explored. However, the majority of the works have demonstrated catalysis selectively only for HER or OER, while bifunctional catalytic activity for overall water-splitting is desired.…”

Bimetallic Cu/Fe MOF-Based Nanosheet Film via Binder-Free Drop-Casting Route: A Highly Efficient Urea-Electrolysis Catalyst

“…On the other hand, despite the demonstration of good electrocatalytic activity for OER and UOR by the state-of-the-art RuO 2 and IrO 2 electrocatalysts, their commercial implementation is limited by the high cost and scarcity of these noble metal-based compounds [ 36 ]. Recently, various transition metal-based materials, such as sulfides [ 37 , 38 , 39 , 40 ], oxides [ 10 , 41 , 42 ], selenides [ 43 , 44 , 45 ] and metal–organic frameworks (MOFs) [ 11 , 46 ] have been investigated with noteworthy catalytic performance for UOR. However, they hardly fulfill the requirement for practical implementation due to their high overpotential and low current densities [ 23 , 26 ].…”

Self‐standing 2D tin‐sulfide‐based heterostructured nanosheets: An efficient overall urea oxidation catalyst

“…Urea naturally decomposes, releasing ammonia gas to atmosphere, which upon aerial oxidation to nitrates, nitrites, or nitrogen oxides. These oxidation products contribute to acid rain formation 10‐13 . Hence, decontamination of urea from wastewater is highly urgent and worthwhile.…”

“…These oxidation products contribute to acid rain formation. [10][11][12][13] Hence, decontamination of urea from wastewater is highly urgent and worthwhile. Meanwhile, green and sustainable energy is also extremely demandable to address future energy crises and to mitigate the excessive use of fossil fuels, which is the major contributor of greenhouse gases.…”