Search

Heterostructure engineering of electrocatalysts provides a fascinating platform to reasonably manipulate the physicochemical properties of nanomaterials and further improve their catalytic efficiency for water electrolysis. However, it still remains a huge challenge to construct well-designed core-shell heterostructured catalysts and identify the key role of components for synergistic catalysis. Herein, a melted polymeric salt tactics was innovatively developed to synthesize heterostructured Ni@Ni(OH)2core-shell nanomaterials supported on porous carbon (named Ni@Ni(OH)2/PC), wherein well-defined Ni(OH)2-Ni heterostructure plays a pivotal role in improving electrocatalytic activity for water reduction and oxidation. Besides, the stable porous carbon support functions as a highway for continuous electron transfer between Ni and Ni(OH)2, and simultaneously enables the full exposure of accessible active sites. The fabricated Ni@Ni(OH)2/PC exhibits outstanding bifunctional electrocatalytic performance for overall water splitting (ƞ10 = 1.55 V) with a good long-time stability. This work sheds new light on the design of engineering heterostructure of active bifunctional electrocatalysts for efficient energy conversion system.

Multifunctional non-precious catalysts for hydrogen/oxygen evolution reaction (HER/OER) and oxygen reduction reaction (ORR) constitute the bottleneck in the applications in electrochemical overall water splitting (OWS) and Zn-air batteries. Herein, a trifunctional electrocatalyst of urchin-like Al,P-codoped Co3O4microspheres supported on Ni foam (denoted as AP-CONPs/NF) was fabricated viaa hydrothermal process and subsequent low-temperature annealing and phosphorization, exhibiting enhanced OER, HER and ORR activities compared with single-doped and undoped samples. Their surface self-organized microstructure and excellent “superaerophobic” feature make a high bubble repellency, which boost diffusion of reactants and electrolyte-electrode intimate contact. The codoping of Al and P elements into Co3O4betters right the balance among surface chemical state, the increased oxygen vacancies and the promoted charge transfer. Encouraged by these synergistic advantages, the AP-CONPs/NF was further employed as excellent bifunctional electrodes for the OWS (low cell voltage of 1.57 V at 10 mA cm−2) and as air cathode for rechargeable Zn-air batteries (high power density of 89.1 mW cm−2), which demonstrates a great feasibility for practical applications.

Developing cost-efficient electrocatalysts for ambient N2-to-NH3conversion and revealing the reaction mechanism are appealing yet challenging tasks. Some transition metal oxides have been recently used to catalyze the nitrogen reduction reaction (NRR), but their further applications are greatly impeded because of their questionable conductivity, poor dispersion, limited active sites, and so forth. Herein, three-dimensional Ni foam-supported urchin-like Al-doped Co3O4nanospheres rich in surface oxygen vacancies (Al-Co3O4/NF) were prepared via a hydrothermal process and subsequent annealing treatment. It is shown that introducing Al atoms into Co3O4effectively tunes the electronic properties of the catalyst, and the increased surface oxygen vacancies induced by Al doping facilitate the activation of nitrogen. What is more, this urchin-like nanostructure, demonstrating an ability to limit the coalescence of gas bubbles, enables the rapid removal of small gas bubbles and better exposure of active sites to N2, thus yielding an impressive ammonia electrosynthesis activity (NH3yield rate: 6.48 × 10–11mol s–1cm–2; Faradaic efficiency: 6.25%) in 0.1 M KOH. Electrochemical-based in situ Fourier transform infrared spectroscopy was employed to study the mechanism of NRR, indicating an associative alternating pathway.

The catalytic activities displayed by single-atom catalysts (SACs) depend on the coordination structure. SACs supported on carbon materials often adopt saturated coordination structures with uneven distributions because they require high-temperature conditions during synthesis. Herein, bisnitrogen-chelated Co SACs that are coordinatively unsaturated are prepared by integrating a Co complex into a conjugated microporous polymer (CMP-CoN2). Compared with saturated analogues, i.e., tetranitrogen-chelated Co SACs (denoted as CMP-CoN4), CMP-CoN2exhibits higher electrocatalytic activity in polysulfide conversions due to an enhanced hybridization between the 3d orbitals of the Co atoms and the 3p orbitals of the S atoms in the polysulfide. As a result, sulfur cathodes prepared with CoN2deliver outstanding performance metrics, including a high specific capacity (1393 mA h g–1at 0.1 C), a superior rate capacity (673.2 mA h g–1at 6 C), and a low capacity decay rate (of only 0.045% per cycle at 2 C over 1000 cycles). They also outperform sulfur cathodes that contain CMP-CoN4or CMPs that are devoid of Co SACs. This work reveals how the catalytic activity displayed by SACs is affected by their coordination structures, and the rules that underpin the structure–activity relationship may be extended to designing electrocatalysts for use in other applications.

The impact of CO2 partial pressure ,fluid producing rate and corrosive medium on the CO2 corrosion regularity of N80 steel and the inhibition efficiency of imidazoline inhibitor are investigated respectively through simulation of the actual working environment in the mined-out space of mechanical oil production wells by using high temperature and pressure reactor. According to the results, the corrosion rate of metals increases with CO2 partial pressure but the inhibition efficiency of the inhibitor is hardly affected when CO2 partial pressure in the scope of 1~3MPa. The increase of the fluid producing rate will accelerate the corrosion of metals and the inhibition efficiency will decline. With corrosion inhibitor applied, metals corrode slower in the liquid phase than in the gas in the initial stage, but latterly the corrosion rate is gradually higher than that in the gas phase.