Accelerating the water splitting kinetics of CoP microcubes anchored on a graphene electrocatalyst by Mn incorporation

Tailoring 3D-Printed Electrodes for Enhanced Water Splitting

Alkaline water electrolysis, a promising technology for clean energy storage, is constrained by extrinsic factors in addition to intrinsic electrocatalytic activity. To begin to compare between catalytic materials for electrolysis applications, these extrinsic factors must first be understood and controlled. Here, we modify extrinsic electrode properties and study the effects of bubble release to examine how the electrode and surface design impact the performance of water electrolysis. We fabricate robust and cost-effective electrodes through a sequential three-dimensional (3D) printing and metal deposition procedure. Through a systematic assessment of the deposition procedure, we confirm the close relationship between extrinsic electrode properties (i.e., wettability, surface roughness, and electrochemically active surface area) and electrochemical performance. Modifying the electrode geometry, size, and electrolyte flow rate results in an overpotential decrease and different bubble diameters and lifetimes for the hydrogen (HER) and oxygen evolution reactions (OER). Hence, we demonstrate the essential role of the electrode architecture and forced electrolyte convection on bubble release. Additionally, we confirm the suitability of ordered, Ni-coated 3D porous structures by evaluating the HER/OER performance, bubble dissipation, and long-term stability. Finally, we utilize the 3D porous electrode as a support for studying a benchmark NiFe electrocatalyst, confirming the robustness and effectiveness of 3D-printed electrodes for testing electrocatalytic materials while extrinsic properties are precisely controlled. Overall, we demonstrate that tailoring electrode architectures and surface properties result in precise tuning of extrinsic electrode properties, providing more reproducible and comparable conditions for testing the efficiency of electrode materials for water electrolysis.

Facile synthesis of Fe-doped CoP nanosheet arrays wrapped by graphene for overall water splitting

The development of durable, beneficial, and highly active non-precious metal-based electrocatalysts for hydrogen generation is a vital concern. This study proposes an effective strategy for the construction of Fe doped CoP nanosheet arrays wrapped by graphene (F_0.25CP-G) on nickel foam as an efficient electrocatalyst for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). In this design, the final catalyst possesses a combination of the high conductivity of graphene, great surface porosity, and the intrinsic electrocatalytic activity of the F_0.25CP-G which results in high-performance electrocatalytic activity toward the HER and OER. Therefore, the as-synthesized F_0.25CP-G catalyst can achieve overpotentials of 66 mV and 230 mV for the HER and OER, respectively, in KOH at 10 mA cm^-2. Furthermore, a practical electrolyzer (F_0.25CP-G||F_0.25CP-G) exhibits a current density of 10 mA cm^-2 at 1.60 V along with good durability for 24 h.

Construction of Defect-Rich Ni-Fe-Doped K0.23 MnO2 Cubic Nanoflowers via Etching Prussian Blue Analogue for Efficient Overall Water Splitting

Designing elaborate nanostructures and engineering defects have been promising approaches to fabricate cost-efficient electrocatalysts toward overall water splitting. In this work, a controllable Prussian-blue-analogue-sacrificed strategy followed by an annealing process to harvest defect-rich Ni-Fe-doped K_0.23 MnO₂ cubic nanoflowers (Ni-Fe-K_0.23 MnO₂ CNFs-300) as highly active bifunctional catalysts for oxygen and hydrogen evolution reactions (OER and HER) is reported. Benefiting from many merits, including unique morphology, abundant defects, and doping effect, Ni-Fe-K_0.23 MnO₂ CNFs-300 shows the best electrocatalytic performances among currently reported Mn oxide-based electrocatalysts. This catalyst affords low overpotentials of 270 (320) mV at 10 (100) mA cm^-2 for OER with a small Tafel slope of 42.3 mV dec^-1 , while requiring overpotentials of 116 and 243 mV to attain 10 and 100 mA cm^-2 for HER respectively. Moreover, Ni-Fe-K_0.23 MnO₂ CNFs-300 applied to overall water splitting exhibits a low cell voltage of 1.62 V at 10 mA cm^-2 and excellent durability, even superior to the Pt/C||IrO₂ cell at large current density. Density functional theory calculations further confirm that doping Ni and Fe into the crystal lattice of δ-MnO₂ can not only reinforce the conductivity but also reduces the adsorption free-energy barriers on the active sites during OER and HER.