No abstract

Water electrolysis is a promising source of hydrogen; however, technological challenges remain. Intensive efforts have focused on developing highly efficient and earth-abundant electrocatalysts for water splitting. An effective strategy is proposed, using a bifunctional tubular cobalt perselenide nanosheet electrode, in which the sluggish oxygen evolution reaction is substituted with anodic hydrazine oxidation so as to assist energy-efficient hydrogen production. Specifically, this electrode produces a current density of 10 mA cm at -84 mV for hydrogen evolution and -17 mV for hydrazine oxidation in 1.0 m KOH and 0.5 m hydrazine electrolyte. An ultralow cell voltage of only 164 mV is required to generate a current density of 10 mA cm for 14 hours of stable water electrolysis.

Tuning local spin state of Co centres by Fe doping in cobalt–iron selenides is effective for boosting oxygen evolution.

Iridium (Ir)-based electrocatalysts are widely explored as benchmarks for acidic oxygen evolution reactions (OERs). However, further enhancing their catalytic activity remains challenging due to the difficulty in identifying active species and unfavorable architectures. In this work, we synthesized ultrathin Ir-IrO x /C nanosheets with ordered interlayer space for enhanced OER by a nanoconfined self-assembly strategy, employing block copolymer formed stable end-merged lamellar micelles. The interlayer distance of the prepared Ir-IrO x /C nanosheets was well controlled at ∼20 nm and Ir-IrO x nanoparticles (∼2 nm) were uniformly distributed within the nanosheets. Importantly, the fabricated Ir-IrO x /C electrocatalysts display one of the lowest overpotential (η) of 198 mV at 10 mA cm −2 geo during OER in an acid medium, benefiting from their features of mixed-valence states, rich electrophilic oxygen species (O (II-δ)− ), and favorable mesostructured architectures. Both experimental and computational results reveal that the mixed valence and O (II-δ)− moieties of the 2D mesoporous Ir-IrO x /C catalysts with a shortened Ir−O (II-δ)− bond (1.91 Å) is the key active species for the enhancement of OER by balancing the adsorption free energy of oxygen-containing intermediates. This strategy thus opens an avenue for designing high performance 2D ordered mesoporous electrocatalysts through a nanoconfined selfassembly strategy for water oxidation and beyond.

Exploring active, stable, earth-abundant, low-cost, and high-efficiency electrocatalysts is highly desired for large-scale industrial applications toward the low-carbon economy. In this study, we apply a versatile selenizing technology to synthesize Se-enriched CoFeSe catalysts on nickel foams for oxygen evolution reactions (OERs) and disclose the relationship between the electronic structures of CoFeSe (via regulating the atom ratio of Co/Fe) and their OER performance. Owing to the fact that the electron configuration of the CoFeSe compounds can be tuned by the incorporated Fe species (electron transfer and lattice distortion), the catalytic activity can be adjusted according to the Co/Fe ratios in the catalyst. Moreover, the morphology of CoFeSe is also verified to strongly depend on the Co/Fe ratios, and the thinner CoFeSe nanosheets are obtained upon selenization treatment, in which it allows more active sites to be exposed to the electrolyte, in turn promoting the OER performance. The CoFeSe nanosheets not only exhibit superior OER performance with a low overpotential of 217 mV at 10 mA cm and a small Tafel slope of 41 mV dec but also possess ultrahigh durability with a dinky degeneration of 4.4% even after 72 h fierce water oxidation test in alkaline solution, which outperforms the commercial RuO catalyst. As expected, the CoFeSe nanosheets have shown great prospects for practical applications toward water oxidation.

Ni3Se4 nanorod arrays are versatile and efficient electrocatalysts for different electrochemical oxidation reactions in hybrid water electrolysis.

No abstract

No abstract