Mo‐/Co‐N‐C Hybrid Nanosheets Oriented on Hierarchical Nanoporous Cu as Versatile Electrocatalysts for Efficient Water Splitting

Abstract

Designing robust and cost‐effective electrocatalysts based on Earth‐abundant elements is crucial for large‐scale hydrogen production through electrochemical water splitting. Here, nitrogen‐doped carbon engrafted Mo2N/CoN hybrid nanosheets that are seamlessly oriented on hierarchical nanoporous Cu scaffold (Mo‐/Co‐N‐C/Cu), as highly efficient electrocatalysts for alkaline hydrogen evolution reaction are reported. The constituent heterostructured Mo2N/CoN nanosheets work as bifunctional electroactive sites for both water dissociation and adsorption/desorption of hydrogen intermediates while the nitrogen‐doped carbon bridges electron transfers between electroactive sites and interconnective Cu current collectors by making use of Mo‐/Co‐N‐C bonds and intimate C/Cu contacts at interfaces. As a consequence of unique architecture having electroactive sites to be sufficiently accessible, self‐supported nanoporous Mo‐/Co‐N‐C/Cu hybrid electrodes exhibit outstanding electrocatalysis in 1 m KOH, with a negligible onset overpotential and a low Tafel slope of 47 mV dec−1. They only take overpotential of as low as 230 mV to reach current density of 1000 mA cm−2. When coupled with their electro‐oxidized derivatives that mediate efficiently the oxygen evolution reaction, the alkaline water electrolyzer can achieve ≈100 mA cm−2 at 1.622 V in 1 m KOH electrolyte, ≈0.343 V lower than the device constructed with commercially available Pt/C and Ir/C nanocatalysts immobilized on nanoporous Cu electrodes.

Interface Engineering of Co/CoMoN/NF Heterostructures for High‐Performance Electrochemical Overall Water Splitting

“…The peaks with the binding energies at 230.7 and 232.8, and 234.6 and 235.9 eV can be attributed to Mo 4+ and Mo 6+ , respectively, [21,37,39,40] suggesting the existence of a small amount of Mo oxides such as MoO 2 and MoO 3 on the surface of Co/CoMoN/NF heterostructures due to surface oxidation. The Mo 3p and N 1s spectrum (Figure 2d) shows three peaks at 399.4, 397.7, and 395.6 eV, corresponding to Mo 3p 3/2 , [21,35] N-Mo/Co, [35,39] and N-H [21] bonds, respectively. For CoMoN/NF electrode, the peaks corresponded to the metallic Co 0 disappear, confirming that the Co NPs were removed after acid treatment.…”

“…As for Co/CoMoN/NF heterostructures, two peaks with the binding energies of 778.6 and 793.7 eV are observed in the Co 2p spectrum (Figure 2b), which corresponds to the Co 2p 3/2 and Co 2p 1/2 of metallic Co 0 , [ 31,34 ] indicating the presence of Co 0 NPs. Two peaks at 781.4 and 797.2 eV can be ascribed to the CoN bonds [ 35,36 ] of CoMoN phase. Another two peaks located at 784.4 and 800.6 eV are the Co 2+ 2p 3/2 and Co 2+ 2p 1/2 due to surface oxidation.…”

“…Another two peaks located at 784.4 and 800.6 eV are the Co 2+ 2p 3/2 and Co 2+ 2p 1/2 due to surface oxidation. [ 37,38 ] For Mo 3d spectrum (Figure 2c), two peaks at 229.7 and 233.9 eV can be attributed to MoN bonds [ 35 ] of CoMoN phase. The peaks with the binding energies at 230.7 and 232.8, and 234.6 and 235.9 eV can be attributed to Mo 4+ and Mo 6+ , respectively, [ 21,37,39,40 ] suggesting the existence of a small amount of Mo oxides such as MoO 2 and MoO 3 on the surface of Co/CoMoN/NF heterostructures due to surface oxidation.…”

Co/MoC Nanoparticles Embedded in Carbon Nanoboxes as Robust Trifunctional Electrocatalysts for a Zn–Air Battery and Water Electrocatalysis

“…(1) The rational coupling of Co and MoC phases into one advanced structure can accelerate the interfacial charge-transfer between adjacent domains, thus significantly reducing the adsorption free energy of the intermediate and enhancing the trifunctional electrochemical performance in terms of excellent activity and high long-term durability for OER, ORR, and HER . (2) Favorable hollow structure features give the Co@IC/MoC@PC catalyst a higher electrochemical active area, thus facilitating the involved electrocatalytic reactions. − (3) The N-doped carbon matrix can effectively protect its inner core of Co/MoC from corrosion and poisoning of the electrolyte, thereby delaying or preventing the deactivation of the catalyst. , (4) The carbon matrix possesses the characteristics of nitrogen doping and high graphitization, which can increase the conductivity of the catalyst, thus leading to fast charge transports during the electrocatalytic reactions. − …”

Research Progress and Application of Single-Atom Catalysts: A Review

“…As a simple and efficient method for hydrogen production and oxygen production, electrocatalytic water-splitting is widely used in industrial production [81]. The use of catalyst electrocatalytic water-splitting is an effective way to prepare hydrogen fuel [82], which can realize the conversion and use of high-efficiency renewable energy [83].…”