The corrosion behavior of A106 carbon steel in 30 wt.% piperazine (PZ, a cycling amine) solutions was investigated by potentiodynamic polarization, EIS, LPR, SEM/EDS, and XRD. For comparison, the corrosion was also conducted in the benchmark solvent of monoethanolamine (MEA) solution. Similar to MEA, initial corrosion testing results in PZ solvent showed that the corrosion rate increases with increases either in CO2 loading from 0.23 to 0.43 mol CO2/mol alkalinity (C/N) or in temperature from 20 to 80 oC. Short term corrosion investigations showed an approximately two orders of magnitude lower corrosion rate for A106 in 0.43 C/N CO2 loaded 30 wt.% PZ at 80 oC than in the same conditions but with 30 wt.% MEA. The difference was due to the ability to form a dense and protective FeCO3 layer on the metal surface in PZ as opposed to in MEA solutions. Possible mechanisms are discussed.

The corrosion inhibition of 2-mercaptobenzimidazole on A106 carbon steel and its stability in a post-combustion CO2 capture system with application of 5 M monoethanolamine aqueous solutions has been evaluated by linear polarization resistance, electrochemical impedance spectroscopy, immersion corrosion testing, scanning electron microscopy/energy dispersive spectroscopy, x-ray diffraction, and liquid chromatography-mass spectroscopy. Although no notable layer of protective corrosion product was found on the A106 surface at 80°C and atmospheric pressure for >180 h, corrosion was inhibited, and its polarization resistance increased nearly an order of magnitude when 2-mercaptobenzimidazole was added. However, degradation of 2-mercaptobenzimidazole, associated with the formation of an FeS layer with cracks, occurred at 108°C and 4.13×105 Pa.

Electrolyte-accessibly porous yet densely packed MXene composite electrodes with high ion-accessible surface and rapid ion transport rate have shown exceptional promise for high-volumetric-performance supercapacitors (SCs), but they are largely limited by the insufficient rate capability and poor electrochemical cyclability, in association with the instability in mechanical robustness of the porous network structures. Taking advantage of chemical bonding design, herein a black phosphorus (BP)@MXene compact film of 3D porous network structure is successfully made by in situ growth of BP nanoparticles on crumbled MXene flakes. The strong interfacial interaction (Ti−O−P bonds) formed at the BP− MXene interfaces not only enhances the atomic charge polarization in the BP−MXene heterostructures, leading to efficient interfacial electron transport, but also stabilizes the 3D porous yet dense architecture with much improved mechanical robustness. Consequently, fully packaged SCs using the BP@MXene composite films with a practical-level of mass loading (∼15 mg cm −2 ) deliver a high stack volumetric energy density of 72.6 Wh L −1 , approaching those of lead-acid batteries (50−90 Wh L −1 ), together with a long-term stability (90.58% capacitance retention after 50000 cycles). The achievement of such high energy density bridges the gap between traditional batteries and SCs and represents a timely breakthrough in designing compact electrodes toward commercial-level capacitive energy storage.

The corrosion behavior of A106 carbon steel in piperazine, an advanced alternative postcombustion CO2 capture solvent to monoethanolamine, has been investigated. Electrochemical corrosion testing methods such as linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) have been used to evaluate the corrosion of A106 in 0.43 mol CO2/mol alkalinity (C/N) loaded 30 wt % piperazine at 80 °C for 150 h. In addition, immersion corrosion has been carried out up to 1050 h in a traditional corrosion cell with the same CO2 loaded solution but at 100 °C and 110 psi. Subsequently, as-corroded A106 samples were characterized by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD). The results showed that a sharp decrease in the corrosion rate occurred before reaching a steady-state corrosion process. This was due to the growth of a protective and stable layer of FeCO3. Possible mechanisms are discussed.