No abstract

Exploration of high‐efficiency, economical, and ultrastable electrocatalysts for the oxygen reduction reaction (ORR) to substitute precious Pt is of great significance in electrochemical energy conversion devices. Single‐atom catalysts (SACs) have sparked tremendous interest for their maximum atom‐utilization efficiency and fascinating properties. Therefore, the development of effective synthetic methodology toward SACs becomes highly imperative yet still remains greatly challenging. Herein, a reliable SiO2‐templated strategy is elaborately designed to synthesize atomically dispersed Fe atoms anchored on N‐doped carbon nanospheres (denoted as Fe–N–C HNSs) using the cheap and sustainable biomaterial of histidine (His) as the N and C precursor. By virtue of the numerous atomically dispersed Fe–N4 moieties and unique spherical hollow architecture, the as‐fabricated Fe–N–C HNSs exhibit excellent ORR performance in alkaline medium with outstanding activity, high long‐term stability, and superior tolerance to methanol crossover, exceeding the commercial Pt/C catalyst and most previously reported non‐precious‐metal catalysts. This present synthetic strategy will provide new inspiration to the fabrication of various high‐efficiency single‐atom catalysts for diverse applications.

Nanostructured WO(3) has been developed as a promising water-splitting material due to its ability of capturing parts of the visible light and high stability in aqueous solutions under acidic conditions. In this review, the fabrication, photocatalytic performance and operating principles of photoelectrochemical cells (PECs) for water splitting based on WO(3) photoanodes, with an emphasis on the last decade, are discussed. The morphology, dimension, crystallinity, grain boundaries, defect and separation, transport of photogenerated charges will also be mentioned as the impact factors on photocatalytic performance.

The lack of high-efficient, low-cost, and durable bifunctional electrocatalysts that act simultaneously for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is currently one of the major obstacles to commercializing the electrical rechargeability of zinc-air batteries. A nanocomposite CoO-NiO-NiCo bifunctional electrocatalyst supported by nitrogen-doped multiwall carbon nanotubes (NCNT/CoO-NiO-NiCo) exhibits excellent activity and stability for the ORR/OER in alkaline media. More importantly, real air cathodes made from the bifunctional NCNT/CoO-NiO-NiCo catalysts further demonstrated superior performance to state-of-the-art Pt/C or Pt/C+IrO2 catalysts in primary and rechargeable zinc-air batteries.

No abstract

Oxygen electrocatalysis, namely of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), governs the performance of numerous electrochemical energy systems such as reversible fuel cells, metal-air batteries, and water electrolyzers. However, the sluggish kinetics of these two reactions and their dependency on expensive noble metal catalysts (e.g, Pt or Ir) prohibit the sustainable commercialization of these highly innovative and in-demand technologies. Bifunctional perovskite oxides have emerged as a new class of highly efficient non-precious metal catalysts (NPMC) for oxygen electrocatalysis in alkaline media. In this review, we discuss the state-of-the-art understanding of bifunctional properties of perovskites with regards to their OER/ORR activity in alkaline media and review the associated reaction mechanisms on the oxides surface and the related activity descriptors developed in the recent literature. We also summarize the present strategies to modify their electronic structure and to further improve their performance for the ORR/OER through highlighting the new concepts relating to the role of surface redox chemistry and oxygen deficiency of perovskite oxides for the ORR/OER activity. In addition, we provide a brief account of recently developed advanced perovskite-nanocarbon hybrid bifunctional catalysts with much improved performances.

Rational design and construction of a multifunctional electrocatalyst featuring with high efficiency and low cost is fundamentally important to realize new energy technologies. Herein, a trifunctional electrocatalyst composed of FePx nanoparticles and Fe–N–C moiety supported on the N‐, P‐codoped carbon (NPC) is masterly synthesized by a facile one‐pot pyrolysis of the mixture of tannic acid, ferrous chloride, and sodium hydrogen phosphate. The synergy of each component in the FePx/Fe–N–C/NPC catalyst renders high catalytic activities and excellent durability toward both oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The electrocatalytic performance and practicability of the robust FePx/Fe–N–C/NPC catalyst are further investigated under the practical operation conditions. Particularly, the overall water splitting cell assembled by the FePx/Fe–N–C/NPC catalyst only requires a voltage of 1.58 V to output the benchmark current density of 10 mA cm−2, which is superior to that of IrO2–Pt/C‐based cell. Moreover, the FePx/Fe–N–C/NPC‐based zinc–air batteries deliver high round‐trip efficiency and remarkable cycling stability, much better than that of Pt/C–IrO2 pair‐based batteries. This work offers a new strategy to design and synthesize highly effective multifunctional electrocatalysts using cheaper tannic acid derived carbon as support applied in electrochemical energy devices.

Rational designing of the composition and structure of electrode material is of great significance for achieving highly efficient energy storage and conversion in electrochemical energy devices. Herein, MoS2/NiS yolk–shell microspheres are successfully synthesized via a facile ionic liquid‐assisted one‐step hydrothermal method. With the favorable interface effect and hollow structure, the electrodes assembled with MoS2/NiS hybrid microspheres present remarkably enhanced electrochemical performance for both overall water splitting and asymmetric supercapacitors. In particular, to deliver a current density of 10 mA cm−2, the MoS2/NiS‐based electrolysis cell for overall water splitting only needs an output voltage of 1.64 V in the alkaline medium, lower than that of Pt/C–IrO2‐based electrolysis cells (1.70 V). As an electrode for supercapacitors, the MoS2/NiS hybrid microspheres exhibit a specific capacitance of 1493 F g−1 at current density of 0.2 A g−1, and remain 1165 F g−1 even at a large current density of 2 A g−1, implying outstanding charge storage capacity and excellent rate performance. The MoS2/NiS‐ and active carbon‐based asymmetric supercapacitor manifests a maximum energy density of 31 Wh kg−1 at a power density of 155.7 W kg−1, and remarkable cycling stability with a capacitance retention of approximately 100% after 10 000 cycles.