Surface-adsorbed phosphate boosts bifunctionally electrocatalytic activity of Ni0.9Fe0.1S for hydrogen production

Amorphous/crystalline nanostructured Co-FeOOH/CoCe-MOF/NF heterojunctions for efficient electrocatalytic overall water splitting

Hydrogen production by electrocatalytic water splitting is considered to be an effective and environmental method, and the design of an electrocatalyst with high efficiency, low cost, and multifunction is of great importance. Herein, we developed a amorphous Co-FeOOH/crystalline CoCe-MOF heterostructure (defined as Co-FeOOH/CoCe-MOF/NF) though a convenient cathodic electrodeposition strategy as a high-efficiency bifunctional electrocatalyst for water electrolysis. The Co-FeOOH/CoCe-MOF/NF nanocrystals provide remarkable electronic conductivity and plenty of active sites, and the crystalline/amorphous heterostructure with generates synergistic effects, providing plentiful active sites and efficient charge/mass transfer. Benefiting from this, the designed Co-FeOOH/CoCe-MOF/NF displays ultralow overpotentials of 226 and 74 mV to achieve 10 mA cm-2 for oxygen evolution reaction and hydrogen evolution reaction, and also shows the superior performance for overall water splitting with a low voltage of 1.55 V at 10 mA cm-2 in 1 M KOH. The work reveals a design of superior activity, cost-effective and multifunctional electrocatalysts for water splitting.

Unraveling the crucial contribution of additive chromate to efficient and stable alkaline seawater oxidation on Ni-based layered double hydroxides

Seawater electrolysis to generate hydrogen offers a clean, green, and sustainable solution for new energy. However, the catalytic activity and durability of anodic catalysts are plagued by the corrosion and competitive oxidation reactions of chloride in high concentrations. In this study, we find that the additive CrO42- anions in the electrolyte can not only promote the formation and stabilization of the metal oxyhydroxide active phase but also greatly mitigate the adverse effect of Cl- on the anode. Linear sweep voltammetry, accelerated corrosion experiments, corrosion polarization curves, and charge transfer resistance results indicate that the addition of CrO42- distinctly improves oxygen evolution reaction (OER) kinetics and corrosion resistance in alkaline seawater electrolytes. Especially, the introduction of CrO42- even in the highly concentrated NaCl (2.5 M) electrolyte prolongs the durability of NiFe-LDH to almost five times the case without CrO42-. Density functional theory calculations also reveal that the adsorption of CrO42- can tune the electronic configuration of active sites of metal oxyhydroxides, enhance conductivity, and optimize the intermediate adsorption energies. This anionic additive strategy can give a better enlightenment for the development of efficient and stable oxygen evolution reactions for seawater electrolysis.