HIGHLIGHTS • Molybdenum aluminum boride single crystals as layered ternary borides were firstly applied for the electrochemical N 2 reduction reaction under ambient conditions and in alkaline media, displaying excellent electrocatalytic performances at the low overpotential. • Through the combination of the strong interaction of Al/B band and N orbitals and the special crystal structure exposing more active sites, synergistic effect of the elements was verified to achieve the enhancement of N 2 reduction reaction process and the limitation of hydrogen evolution reaction.

MAB phases are a new class of layered ternary materials that have already shown a number of outstanding properties. Here, we investigate defect evolution and radiation tolerance of two MAB phases, MoAlB and Fe2AlB2, using a combination of experimental characterization and firstprinciples calculations. We find that Fe2AlB2 is more tolerant to radiation-induced amorphization than MoAlB, both at 150 °C and at 300 °C. The results can be explained by the fact that the Mo Frenkel pair is unstable in MoAlB and as a result, irradiated MoAlB is expected to have a significant concentration of MoAl antisites, which are difficult to anneal even at 300 °C. We find that the tolerance to radiation-induced amorphization of MAB phases is lower than in MAX phases, but it is comparable to that of SiC. However, MAB phases do not show radiation-induced cracking which is observed in MAX phases under the same irradiation conditions. This study suggests that MAB phases might be a promising class of materials for applications that involve radiation.

The reaction between oxygen and sulphite in the presence of cobalt(1r) as catalyst has been studied at the low concentrations which are of interest in relation to water treatment processes employed in the ' waterflood ' secondary oil-recovery technique. A continuous-flow apparatus was used to study reaction times of 0.1-1.7 s using iodine titration of the sulphite to follow the reaction, and initial concentrations of sulphite 0.35-1.13 mmol dmP3, oxygen 0.029-0.22 mmol dm-3 and cobalt 0.20-25.3 pmol drnp3. A static method was used to measure sulphite as a function of time at lower concentrations, using the fuschin-formaldehyde method. Reaction times were 2-60 min, with initial concentrations of sulphite 10-62, oxygen 3.422 and cobalt 0.01-0.05 pmol dmP3.In both concentration ranges the reaction showed an induction period during which little or no reaction occurred, followed by an almost linear decay in sulphite concentration. The orders of reaction with respect to sulphite and oxygen were 1.5 and 0 over the whole concentration range studied. However, the order with respect to cobalt increased from 0.5 to 1.5 on moving to the lower concentrations, and a general rate equation is developed to express the experimental rate behaviour :The activation energy in the low-concentration range was found to be 183 kJ mol-l. Added hydroquinone inhibited the reaction strongly and a chain mechanism is proposed involving reaction via a series of cobalt complex intermediates.

Kinetic aspects of the sulfite-oxygen reaction have been studied at very low concentrations (ca. 50 and 11 µ dm™3 of S032™ and 02, respectively). Neither sodium sulfite nor ammonium bisulfite reacts appreciably in the absence of a catalyst. In the presence of cobalt(II) (19-48 nmol dm™3), the ammonium salt reacts ca. 2.5 times more slowly than the sodium salt. The strong variation of rate with pH was an interesting and unexplained effect. Natural seawater was found to exhibit variable but substantial catalytic activity. Studies in synthetic seawater showed that (in order of reactivity) Co(II) > Cu(II) » Ce(IV) > Mn(II) were active catalysts, while Ni(II), Fe(II), and Fe (III) were inactive. The effect on rate of the high ionic strength of seawater was semiquantitatively consistent with the Bronsted-Bjerrum theory.

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