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

Abstract

Developing efficient electrocatalysts for urea oxidation reaction (UOR) can be a promising alternative strategy to substitute the sluggish oxygen evolution reaction (OER), thereby producing hydrogen at a lower cell-voltage. Herein, we synthesized a binder-free thin film of ultrathin sheets of bimetallic Cu-Fe-based metal–organic frameworks (Cu/Fe-MOFs) on a nickel foam via a drop-casting route. In addition to the scalable route, the drop-casted film-electrode demonstrates the lower UOR potentials of 1.59, 1.58, 1.54, 1.51, 1.43 and 1.37 V vs. RHE to achieve the current densities of 2500, 2000, 1000, 500, 100 and 10 mA cm−2, respectively. These UOR potentials are relatively lower than that acquired by the pristine Fe-MOF-based film-electrode synthesized via a similar route. For example, at 1.59 V vs. RHE, the Cu/Fe-MOF electrode exhibits a remarkably ultra-high anodic current density of 2500 mA cm—2, while the pristine Fe-MOF electrode exhibits only 949.10 mA cm−2. It is worth noting that the Cu/Fe-MOF electrode at this potential exhibits an OER current density of only 725 mA cm—2, which is far inconsequential as compared to the UOR current densities, implying the profound impact of the bimetallic cores of the MOFs on catalyzing UOR. In addition, the Cu/Fe-MOF electrode also exhibits a long-term electrochemical robustness during UOR.

Quasi-Cu-MOFs: highly improved water stability and electrocatalytic activity toward H2O2 reduction among pristine 3D MOFs

“…[1][2][3] The majority of MOFs have a large number of properties, including porous structure, high surface area, and exible composition. [4][5][6][7][8] As a result, MOFs have been widely used in gas storage, 9,10 electrochemical catalysis, [11][12][13][14][15][16] and drug delivery [17][18][19][20] due to these unique properties. Recently, some pristine MOFs with different metal centers (such as Fe, Cu and Co) have been reported with an instinct enzyme-mimicking catalytic activity.…”

In situ growth of bimetal–organic framework-derived phosphides on conductive substrate materials as bifunctional electrocatalysts for overall water splitting

“…Because the intrinsically slow kinetics of electrocatalytic water splitting limits the activity of the OER and HER, and it is difficult to reduce the overpotential during water electrolysis, especially at large current densities. 3,4 Therefore, developing highly active and stable catalysts to reduce overpotentials and improve reaction rates at large current densities is the top priority for all researchers in the world. The most popular catalysts for water electrolysis are Pt/C, RuO 2 and IrO 2 , [5][6][7] all of which have ultra-high catalytic activity.…”

Two new Ni/Co-MOFs as electrocatalysts for the oxygen evolution reaction in alkaline electrolytes

“…The optimized NC-PB@CNT film is shown to provide an outstanding overall-water splitting performance with a low cell voltage of 1.66 Vat a rate of 50 mA cm À2 , along with an excellent long-term cell durability of more than 100 h. 30 And the bimetallic Cu/Fe-MOF film can be a highly efficient UOR catalyst. 31 Most of the recent literatures on MOF OER catalysts shows that the coordinatively unsaturated metal site (CUMs) is a key for notable OER activity, 32,33 where the metal centers are incompletely blocked by the organic ligands or residual solvents. After removing residual solvents, coordinatively OMSs can be created, and these exposed atomically-dispersed metal ions can act as the highly active catalytic sites in electrocatalysis, which show high adsorption affinity and catalytic activity.…”

“…The optimized NC-PB@CNT film is shown to provide an outstanding overall-water splitting performance with a low cell voltage of 1.66 Vat a rate of 50 mA cm −2 , along with an excellent long-term cell durability of more than 100 h. 30 And the bimetallic Cu/Fe-MOF film can be a highly efficient UOR catalyst. 31…”