Overall Water Splitting In Alkaline Media Research Articles

Three-dimensional Cobalt-MOF/ CNF microstructured assembly as a bifunctional electrocatalyst for effective overall water-splitting in alkaline media

The electrocatalyst Co-MOF/CNF microstructure exhibits excellent stability and charge transfer efficiency synthesized via ultrasonication technique. The composite has a lower Rct value of 2 Ω. The larger Cdl value of Co-MOF/CNF (12.3 mF/dec) is responsible for the high catalytic activity for both HER and OER reactions. The composite has strong catalytic activity in HER and OER, with low overpotentials of 193 mV and 250 mV at 10 mA/cm2. Furthermore, excellent water electrolyzer activity was achieved by Co-MOF/CNF||Co-MOF/CNF with a cell voltage of 1.49 V at 10 mA/cm2 and is stable over 24 h, proving the long-term efficacy in sustainable energy systems.

Binary Co9S8–NiCo2S4 anchored on N-doped rGO backbone as an efficient bifunctional and durable hetero-catalyst for overall water-splitting in alkaline medium

A schematic illustration depicting the electrochemical water splitting by Co9S8–NiCo2S4/N-rGO heterocatalyst.

Combined nano/micro-structure of Ni12P5-Ni2P nanorod array for effective wide pH range HER and overall alkaline water-splitting

• A self-supported Ni 12 P 5 -Ni 2 P-NR@NF was fabricated. • The Ni 12 P 5 -Ni 2 P-NR@NF demonstrated excellent HER (ŋ 10 was 107 mV, 138 mV and 168 mV in acidic, neutral and alkaline electrolyte, respectively) and overall water-splitting activity (ŋ 20 = 1.53 V, with stability of ∼120 h) in alkaline media. • The combination of unique structure and intrinsic chemical properties was responsible for the excellent electrocatalysis performance of Ni 12 P 5 -Ni 2 P-NR@NF. A self-supported Ni phosphide nanorod array (Ni 12 P 5 -Ni 2 P-NR@NF) was synthesized using a one-step method to produce a multifunctional electrocatalyst. Benefiting from the unique structure and intrinsic chemical properties, the Ni 12 P 5 -Ni 2 P-NR@NF demonstrated excellent HER activity across a range of pH values and overall water-splitting in alkaline media. To achieve a current density of 10 mA cm −2 , the optimized Ni 12 P 5 -Ni 2 P-NR@NF required an overpotential of 107 mV, 138 mV and 168 mV in acidic, neutral and alkaline electrolyte, respectively. In addition, when used as both anode and cathode for a two-electrode electrolyze to perform water electrolysis in 1.0 M KOH, the cell only needed 1.53 V to achieve 20 mA cm −2 with stability of ∼120 h, providing evidence of multifunctional potential for large-scale applications.

In-situ transformation to accordion-like core-shell structured metal@metallic hydroxide nanosheet from nanorod morphology for overall water-splitting in alkaline media

Exploring highly-efficient, low-cost and earth-abundant bi-functional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have a key role in economical overall water-splitting. Herein, a facile and general route is developed to prepare various non-noble metal-based electrocatalysts via NH3⋅H2O treatment (NT) on Ni foam (NF) (M-NT/NF, M = Co, Ni, Fe, Mn, Cu). The morphology and compositions of the obtained catalysts could be tuned via solvothermal process with NH3⋅H2O, and then optimizing the active sites exposure and effectively change the reaction kinetics of the electrocatalytic reaction. Moreover, the substrate of Ni foam is in favor of electrolyte transfer and release of produced gases. Then, the obtain Co-NT/NF, composed of metallic Co and Co(OH)2, exhibits excellent catalytic performance for HER with low overpotential of 178 mV@10 mA cm−2 and small Tafel slope of 75 mV dec−1, which is rarely reported for HER. For OER, only a low overpotential of 226 mV is required to deliver 10 mA cm−2 with a small Tafel slope of 46 mV dec−1. Moreover, the reported electrocatalysts present negligible current density loss during long-term stability measurement, demonstrating robust nanostructure feature of the prepared catalysts. This work opens a facile and efficient avenue to design bi-funtional electrocatalyst coupling with outstanding catalytic performance.

Novel CoP Hollow Prisms as Bifunctional Electrocatalysts for Hydrogen Evolution Reaction in Acid media and Overall Water-splitting in Basic media

Cobalt phosphide (CoP) with hollow prisms nanostructure has been successfully synthesized via a facile two-step micro-assisted method. Firstly, uniform Co3(CH3COO)5(OH) cubes are prepared by microwave method. Then as-prepared Co3(CH3COO)5(OH) cubes as precursors have been conducted by phosphorization at low temperature. Novel CoP hollow prisms with 1μm length, 500nm width and 500nm height have been synthesized. The obtained CoP hollow prisms can be used as both an efficient electrocatalyst for HER in acid media (0.5M H2SO4 solution) and a remarkable bifunctional electrocatalyst for overall water-splitting in alkaline media (1.0M KOH solution) which might be attributed to their high surface area, porosity and good distribution. The OER mechanisms of CoP in alkaline solution have been investigated through XPS and SEM Mapping, which demonstrate that the amorphous oxygen-containing nanostructure on the surface of CoP may be the real catalytic active species. In addition, phosphidation of uniform cobalt salt hydrates precursor with specific structure at low temperature is a newfangled and effective strategy to synthesis bifunctional electrocatalyst CoP.