Highly Synergistic Co³⁺ and Pyridinic‐N‐Rich Bifunctional Electrocatalyst for Ultra‐Low Energy‐Driven Effective Hydrogen Production and Urea Oxidation

Abstract

Metal–organic framework (MOF)‐derived electrocatalysts exhibit enhanced electrochemical water splitting with significant durability. However, they cannot drive the required current density at a lower overpotential (η) compared to other benchmark catalysts. To overcome the lack of efficient catalytic activity, Co3O4‐embedded nitrogen‐doped carbon (NC) is fabricated on NiO nanosheets derived from an in situ synthesized Co MOF with an electrodeposited (Ni(OH)2) layer. The electrocatalyst developed herein comprises many Co3+, Ni3+, and pyridinic‐N‐exposed active centers and exhibits an excellent synergistic effect between the metal oxide–NC–metal oxide, facilitating a highly efficient hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Owing to the highly intimate contact between the electrocatalyst layers, rapid electron transfer occurs and a current density of 10 mA cm‐2 is produced in the HER and OER at η of 73 and 110 mV, respectively, with excellent mass activity and high turnover frequency. However, urea‐assisted water electrolysis achieves current densities of 10 and 100 mA cm‐2 at cell voltages of just 1.31 and 1.49 V, respectively, for the two‐electrode‐based system, with an extremely stable durability of 212 h (1.49 V). Co3O4@NC/NiO ∥ Co3O4@NC/NiO has a considerably better urea electrolysis performance than other benchmark electrocatalysts.

Iron–Cobalt Nanoparticles Embedded in B,N-Doped Chitosan-Derived Porous Carbon Aerogel for Overall Water Splitting

“…It can be deconvoluted into four peaks (Figure g) at 400.88 eV (Graphitic-N), 399.28 eV (Pyrrolic-N), 398.25 eV (B–N), and 397.62 eV (Pyridinic-N/Metallic N) . The N 1s spectrum is dominated by Pyridinic-N/Metallic N species (36.05%), which bodes well for the HER and OER as the Pyridinic-N species is favorable for these reactions. , The presence of the C–B bond in the form of BC 3 in the C 1s spectra at 284.19 eV (Figure S12b) shows that B was successfully doped into the carbon matrix . As shown in Figure h, four prominent peaks can be observed in the B 1s spectrum, ascribed to BC 3 (190.18 eV), B–N (191.03 eV), BC 2 O (191.83), and BCO 2 (192.51 eV). , Doping with B and N may simultaneously substitute two neighboring C atoms in the carbon structure, forming a C–B–N bond.…”

“…36 The N 1s spectrum is dominated by Pyridinic-N/Metallic N species (36.05%), which bodes well for the HER and OER as the Pyridinic-N species is favorable for these reactions. 37,38 The presence of the C−B bond in the form of BC 3 in the C 1s S12b) shows that B was successfully doped into the carbon matrix. 39 As shown in Figure 2h, four prominent peaks can be observed in the B 1s spectrum, ascribed to BC 3 (190.18 eV), B−N (191.03 eV), BC 2 O (191.83), and BCO 2 (192.51 eV).…”

Designing bifunctional catalysts for urea electrolysis: progress and perspectives

“…Constructing oxide-based composite catalysts is another efficient method. Integrating metal oxides with metal particles, 101 alloys, 102 oxides, 103 sulfides, 104 phosphides, 105 and carbon materials 106 has been explored. The introduction of carbon materials can improve the conductivity of catalysts, and the interaction between oxides and carbon ensures long-term stability.…”

Impact of Highly Concentrated Alkaline Treatment on Mesostructured Cobalt Oxide for the Oxygen Evolution Reaction

“…[4] Further, the commercial reagent grade KOH pellet mostly only contains circa 85% of KOH; hence, the presence of impurities could be prominent on the electrocatalyst and the reaction when the concentrated KOH solution is used as an electrolyte.Cobalt oxide spinel is one of the most studied electrocatalysts for oxygen evolution reaction (OER) in the recent decade owing to its tunable morphology and electronic structure. [5][6][7][8][9][10][11][12][13][14][15] However, the spinel phase is not the real catalyst for OER since its surface undertakes a transformation into an oxyhydroxide intermediate active state upon the anodic polarization. [9,16] This phase transformation might take place only at several or subnanometers regions of the catalyst surface, within the vicinity of electrode and electrolyte interfaces.…”