RESUMEN
In the latest geophysical survey crossing the Ninety East Ridge of the Indian Ocean, a new method was employed to perform proportional double seismic source excitation and synchronously receive signals from the sea surface and the seabed. The two seismic sources used for excitation were two sets of gun arrays with different energies and dominant frequencies, a G gun array and a Bolt gun array. The G gun array consisted of 3 G.II guns with a total capacity of 450 in3 and a dominant frequency of 20-100 Hz. The Bolt gun array consisted of 4 Bolt 1500LL air guns with a total capacity of 6000 in3 and a dominant frequency of 10-40 Hz. The seismic receiving system comprised a 480-channel seismic streamer towed from the sea surface and 21 ocean bottom seismometers (OBS). During offshore operations, the integrated navigation system produced equidistant trigger signals at an interval of 50 m. The trigger signals were distributed to the G gun array and Bolt gun array at a ratio of 3:1 after passing through a pulse signal proportional distributor. The two sets of gun arrays fired alternatingly at a given ratio. The receiving equipment on the sea surface and seabed simultaneously received the seismic signals excited by the two sets of gun arrays. After targeted data processing, in addition to the seismic profile generated by the conventional G gun seismic source, the deep seismic profile generated by the Bolt gun seismic source and the survey profile of the active-source OBS were obtained simultaneously. The penetration depths of the three sets of profiles reach 2 km, 6 km, and 30 km, respectively, greatly improving the efficiency of offshore deep-sea seismic surveys.
RESUMEN
An effective yet simple approach was developed to synthesize mesoporous PdBi nanocages for electrochemical applications. This technique relies on the subtle utilization of the hydrolysis of a metal salt to generate precipitate cores in situ as templates for navigating the growth of mesoporous shells with the assistance of polymeric micelles. The mesoporous PdBi nanocages are then obtained by excavating vulnerable cores and regulating the crystals of mesoporous metallic skeletons. The resultant mesoporous PdBi nanocages exhibited excellent electrocatalytic performance toward the ethanol oxidation reaction with a mass activity of 3.56 A mg-1_Pd, specific activity of 17.82 mA cm-2 and faradaic efficiency of up to 55.69% for C1 products.
RESUMEN
Cobalt oxides, including spinel Co3O4 and rock-salt CoO, have been widely reported as promising catalysts for oxygen reduction reaction (ORR). However, three types of cobalt ions, i.e., Co2+ in the tetrahedral site (Co2+ Td), Co3+ in the octahedral site (Co3+ Oh), and Co2+ in the octahedral site (Co2+ Oh), are included in these oxides, and the roles of cobalt geometric occupancy and valance states have remained elusive. Here, for the first time, we investigated the effects of cobalt geometric occupancy on the ORR activity by substituting Co2+ Td and Co3+ Oh of Co3O4 with inactive Zn2+ and Al3+, respectively. The ORR activity decreases in the order of Co3O4 (Co3+ Oh, Co2+ Td) < ZnCo2O4 (Co3+ Oh) ⪠CoAl2O4 (Co2+ Td) in accordance with the ORR overpotentials at the current density of 0.1 mA cmOx-2. Furthermore, by comparatively investigating the activity and stability of Co3O4 (Co3+ Oh) and CoO (Co2+ Oh) nanoparticles, by virtue of the electrochemical technique, the high-resolution transmission electron microscopy, and the in operando fuel cell-X-ray absorption spectroscopy techniques, it was revealed that Co2+ Oh in CoO is the main active site, which under electrochemical conditions tends to transform into Co3+ Oh and form Co3O4 with a hollow structure due to the Kirkendall effect; nevertheless, it retains decent ORR activity due to the formation of the unique hollow structure.