1D/3D Heterogeneous Assembling Body of Cobalt Nitrides for Highly Efficient Overall Hydrazine Splitting and Supercapacitors.

Herein, the construction of a heterostructured 1D/3D CoN-Co2 N@NF (nickel foam) electrode used for thermodynamically favorable hydrazine oxidation reaction (HzOR), as an alternative to sluggish anodic oxygen evolution reaction (OER) in water splitting for hydrogen production, is reported. The electrode exhibits remarkable catalytic activities, with an onset potential of -0.11 V in HzOR and -71 mV for a current density of 10 mA cm-2 in hydrogen evolution reaction (HER). Consequently, an extraordinary low cell voltage of 53 mV is required to achieve 10 mA cm-2 for overall hydrazine splitting in a two-electrode system, demonstrating significant energy-saving advantages over conventional water splitting. The HzOR proceeds through the 4e- reaction pathway to release N2 while the 1e- pathway to emit NH3 is uncompetitive, as evidenced by differential electrochemical mass spectrometric measurements. The X-ray absorption spectroscopy, in situ Raman spectroscopy, and theoretical calculations identify cobalt nitrides rather than corresponding oxides/(oxy)hydroxides as catalytic species for HzOR and illustrate advantages of heterostructured CoN-Co2 N in optimizing adsorption energies of intermediates/reagents and promoting catalytic activities toward both HzOR and HER. The CoN-Co2 N@NF is also an excellent supercapacitive material, exhibiting an increased specific capacity (938 F g-1 at 1 A g-1 ) with excellent cycling stability (95.8%, 5000 cycles).

Manipulating Dual-Metal Catalytic Activities toward Organic Upgrading in Upcycling Plastic Wastes with Inhibited Oxygen Evolution.

Electrorefinery of polybutylene terephthalate (PBT) waste plastic, specifically conversion of a PBT-derived 1,4-butanediol (BDO) monomer into value-added succinate coupled with H2 production, emerges as an auspicious strategy to mitigate severe plastic pollution. Herein, we report the synthesis of Mn-doped NiNDA nanosheets (NDA: 2,6-naphthalenedicarboxylic acid), a metal-organic framework (MOF) through a ligand exchange method, and its utilization for electrocatalytic BDO oxidation to succinate. Interestingly, the transformation of doped layered-hydroxide (d-LH) precursors to MOF promotes BDO oxidation while hindering the competitive oxygen evolution reaction. Experimental and theoretical results indicate that the MOF has a higher affinity (i.e., alcoholophilic) for BDO than the d-LH, while Mn doping into NiNDA results in electron accumulation at Ni sites with an upward shift in the d-band center and convenient spin-dependent charge transfer, which are all beneficial for BDO oxidation. The as-constructed two-electrode membrane-electrode assembly (MEA) flow cell, by coupling BDO oxidation and hydrogen evolution reaction, attains an industrial current density of 1.5 A cm-2@1.82 V at 50 °C, corresponding to a specific energy consumption of 3.68 kWh/Nm3 H2. This represents an energy saving of >25% for hydrogen production on an industrial scale compared to conventional water electrolysis (∼5 kWh/Nm3 H2) in addition to the production of valuable chemicals.