Introducing non-bridging ligand in metal-organic framework-based electrocatalyst enabling reinforced oxygen evolution in seawater.

Using seawater as the replacement of freshwater for electrolysis, with the integration of renewable energy, is deemed as an attractive manner to harvest green hydrogen. However, the complexity of seawater puts forward stricter requirement to the electrocatalyst to alleviate the chlorine electrochemistry and corrosion. Herein, a nanosheet array of NiFe-MOF@Ni2P/Ni(OH)2 is devised by partially substituting terephthalic acid (H2BDC) ligand by ferrocenecarboxylic acid (FcCA). Tailoring the active site into an under-coordinated fashion affords NiFe-MOF@Ni2P/Ni(OH)2 excellent performance towards oxygen evolution reaction (OER), only requiring the overpotentials of 302 mV and 394 mV in alkaline seawater to drive the current densities of 100 and 1000 mA cm-2, respectively. Moreover, the as-obtained electrocatalyst showed robust durability for operating more than 120 h at 500 mA cm-2 under harsh condition (6 M KOH + 1.5 M NaCl, 60 ℃). Density functional theory (DFT) calculations confirmed that tuning the coordination environment of Ni in NiFe-MOF by incorporating the non-bridging FcCA ligands could boost the formation of more active catalytic sites, which can simultaneously enhance the electronic conductivity and accelerate OER kinetics. This work provides beneficial enlightenment of combining MOF-based electrocatalyst with direct electrolysis of seawater.

Interfacial Engineering of Ni/Ni0.2Mo0.8N Heterostructured Nanorods Realizes Efficient 5-Hydroxymethylfurfural Electrooxidation and Hydrogen Evolution.

Simultaneously achieving electrochemical conversion of biomass-derived molecules into value-added products and energy-efficient hydrogen production is a highly attractive strategy but challenging. Herein, we reported a heterostructured Ni/Ni0.2Mo0.8N nanorod array electrocatalyst deposited on nickel foam (Ni/Ni0.2Mo0.8N/NF), which exhibited excellent electrocatalytic activity toward 5-hydroxymethylfurfural (HMF) oxidation, and nearly 100% conversion of HMF and 98.5% yield of 2,5-furandicarboxylic acid (FDCA) products can be achieved. The post-reaction characterizations unveil that Ni species in Ni/Ni0.2Mo0.8N/NF would be readily converted to NiOOH as the real active sites. Furthermore, a two-electrode electrolyzer was assembled with Ni/Ni0.2Mo0.8N/NF utilized as a bifunctional electrocatalyst for both the cathode and anode, giving rise to a low voltage of 1.51 V to concurrently produce FDCA and H2 at 50 mA cm-2. This work enlightens the significance of regulating redox activities of transition metals via interfacial engineering and constructing heterostructured electrocatalysts toward more efficient energy utilization.

Highly active quinone site-enriched carbon nanotube composites for efficient electrocatalytic hydrogen peroxide generation.

We propose a facile and scalable in situ polymerization strategy to selectively introduce the active quinone-based components across the carbon nanotube (CNT) surface. It can be observed that the optimized poly(anthraquinonyl sulfide) (PAQS)/CNT composites exhibit excellent activity and selectivity with a H2O2 yield ratio of approximately 91% at 0.5 V (vs. RHE), together with satisfactory stability at 0.5 V over 20 h. The electrocatalytic performance is correlated with the synergistic effect between PAQS and CNTs. That is, PAQS grafted with abundant quinone groups facilitates the 2 e- ORR process to produce H2O2, and the conductive CNT scaffold is beneficial for the uniform distribution of PAQS and ensures the fast electron transport through the composites.