Roles of Heterojunction and Cu Vacancies in the Au@Cu2-xSe for the Enhancement of Electrochemical Nitrogen Reduction Performance.

The utilization of hydrogen (H2) as a fuel source is hindered by the limited infrastructure and storage requirements. In contrast, ammonia (NH3) offers a promising solution as a hydrogen carrier due to its high energy density, liquid storage capacity, low cost, and sustainable manufacturing. NH3 has garnered significant attention as a key component in the development of next-generation refueling stations, aligning with the goal of a carbon-free economy. The electrochemical nitrogen reduction reaction (ENRR) enables the production of NH3 from nitrogen (N2) under ambient conditions. However, the low efficiency of the ENRR is limited by challenges such as the electron-stealing hydrogen evolution reaction (HER) and the breaking of the stable N2 triple bond. To address these limitations and enhance ENRR performance, we prepared Au@Cu2-xSe electrocatalysts with a core@shell structure using a seed-mediated growth method and a facile hot-injection method. The catalytic activity was evaluated using both an aqueous electrolyte of KOH solution and a nonaqueous electrolyte consisting of tetrahydrofuran (THF) solvent with lithium perchlorate and ethanol as proton donors. ENRR in both aqueous and nonaqueous electrolytes was facilitated by the synergistic interaction between Au and Cu2-xSe (copper selenide), forming an Ohmic junction between the metal and p-type semiconductor that effectively suppressed the HER. Furthermore, in nonaqueous conditions, the Cu vacancies in the Cu2-xSe layer of Au@Cu2-xSe promoted the formation of lithium nitride (Li3N), leading to improved NH3 production. The synergistic effect of Ohmic junctions and Cu vacancies in Au@Cu2-xSe led to significantly higher ammonia yield and faradaic efficiency (FE) in nonaqueous systems compared to those in aqueous conditions. The maximum NH3 yields were approximately 1.10 and 3.64 µg h-1 cm-2, with the corresponding FE of 2.24 and 67.52% for aqueous and nonaqueous electrolytes, respectively. This study demonstrates an attractive strategy for designing catalysts with increased ENRR activity by effectively engineering vacancies and heterojunctions in Cu-based electrocatalysts in both aqueous and nonaqueous media.

Promoting electrochemical ammonia synthesis by synergized performances of Mo2C-Mo2N heterostructure.

Hydrogen has become an indispensable aspect of sustainable energy resources due to depleting fossil fuels and increasing pollution. Since hydrogen storage and transport is a major hindrance to expanding its applicability, green ammonia produced by electrochemical method is sourced as an efficient hydrogen carrier. Several heterostructured electrocatalysts are designed to achieve significantly higher electrocatalytic nitrogen reduction (NRR) activity for electrochemical ammonia production. In this study, we controlled the nitrogen reduction performances of Mo2C-Mo2N heterostructure electrocatalyst prepared by a simple one pot synthesis method. The prepared Mo2C-Mo2N0.92 heterostructure nanocomposites show clear phase formation for Mo2C and Mo2N0.92, respectively. The prepared Mo2C-Mo2N0.92 electrocatalysts deliver a maximum ammonia yield of about 9.6 µg h-1 cm-2 and a Faradaic efficiency (FE) of about 10.15%. The study reveals the improved nitrogen reduction performances of Mo2C-Mo2N0.92 electrocatalysts due to the combined activity of the Mo2C and Mo2N0.92 phases. In addition, the ammonia production from Mo2C-Mo2N0.92 electrocatalysts is intended by the associative nitrogen reduction mechanism on Mo2C phase and by Mars-van-Krevelen mechanism on Mo2N0.92 phase, respectively. This study suggests the importance of precisely tuning the electrocatalyst by heterostructure strategy to substantially achieve higher nitrogen reduction electrocatalytic activity.

Occlusion of Both Vertebral Arteries With Development of Collateral Circulation From the Deep Cervical Artery After Cervical Spine Trauma.

Careful evaluation of vertebral artery injuries is important after cervical translation injuries or transverse foramen fractures. Treatment of trauma can be complicated in cases of concomitant vertebral artery injuries. A 76-year-old woman was admitted to our hospital with left hemiparesis (Motor grade 3) after a motorcycle accident. Cervical spine magnetic resonance imaging (MRI) and computed tomography (CT) revealed a C3 burst fracture and a left C3 lateral mass and lamina fracture. CT angiography revealed fracture fragments that predisposed the vertebral artery to injury throughout its course in the area. CT angiography confirmed that both vertebral arteries were occluded at the C3 fracture site. Subsequent brain MRI revealed acute infarction in the right occipital area. Although both vertebral arteries were occluded, the infarction site did not correspond to the territory supplied by these vessels; therefore, we performed transfemoral cerebral angiography, which revealed collateralization of the bilateral vertebral arteries by the deep cervical artery.. The deep cervical arteries are located between the posterior muscles; therefore, a fixation operation performed using the posterior approach may have affected the collateral circulation and led to exacerbation of the infarction site. Therefore, surgery was performed using an anterior approach and it was possible to minimize the risk of cerebral infarction through preservation of collateral circulation.

Risk Factors and Radiologic Changes in Subsidence after Single-Level Anterior Cervical Corpectomy: A Minimum Follow-Up of 2 Years.

OBJECTIVE: Anterior cervical corpectomy using a titanium mesh cage may result in delayed nonunion and thus a change in cervical alignment, and patients may require revision surgery. We investigated the radiologic and clinical outcomes of cervical corpectomy and the risk factors for subsidence. METHODS: We studied 74 patients who underwent single-level anterior cervical corpectomy for cervical spondylotic myelopathy with or without ossification of the posterior longitudinal ligament between 2007 and 2014. Graft subsidence was considered present when there was a reduction in the anterior and posterior heights by an average of 4 mm or more 2 years after the operation. We measured cervical parameters before surgery, immediately after surgery, and 6, 12, and 24 months after surgery. The clinical outcomes were the neck and arm visual analog scale scores and reoperation rate. RESULTS: In the subsidence group, these values gradually decreased over the 24 months. The radiologic parameters did not differ between the 2 groups for 24 months after the onset of subsidence. There were no differences in clinical outcome or reoperation rate. In the analysis of the risk factors, subsidence occurred with a large T1 slope and a large change in the C27 Cobb angle (p=0.020 and p=0.026, respectively). CONCLUSION: Subsidence gradually occurred after single-level anterior cervical corpectomy for up to 24 months. However, the presence of subsidence did not affect the radiologic and clinical outcomes. When the T1 slope was large and the C27 Cobb angle change was severe, more subsidence occurred.

Anastomosis and Endovascular Treatment of Iatrogenic Vertebral Artery Injury.

Iatrogenic vertebral artery injury (VAI) that occurs during cervical spine surgery can cause life-threatening complications, such as arteriovenous fistulas, catastrophic bleeding, neurological impairment, cerebral ischemia, and death. We report a case of dominant VAI during surgery and the treatment of a 60-year-old man diagnosed with a C1-2-3 metastatic spine tumor from urothelial carcinoma. Active bleeding occurred during tumor resection using pituitary forceps, immediately followed by gauze packing and manual compression. Post further resection, we found that the vertebral artery (VA) was completely severed. After temporary clamping on both sides of the damaged VA, an artificial graft anastomosis was performed. After verifying that the flow was intact using Doppler Sonography, Occiput-C1-4-5-6 posterolateral fusion was performed. Angiography was performed immediately after surgery. We found a thrombus occluding the left VA, and performed mechanical thrombectomy and stent insertion. The final angiography showed good VA flow with no emboli. In this case, VA anastomosis and endovascular treatment were performed within a relatively short period of time post VAI, and the patient was able to recover without any neurological deficits.