Search

Volcano plots and scaling relations are commonly used to design catalysts and understand catalytic behavior. These plots are a useful tool due to their robust and simple analysis of catalysis; however, catalysts that follow the volcano plot paradigm have an inherent limit to their performance. Scaling and Brønsted-Evans-Polanyi (BEP) relations, which are linear correlations in reaction energetics, force tradeoffs when optimizing catalysts, which leads to this limit on performance. Therefore, materials and design strategies that are not limited by volcano plots and scaling relations are of high interest, and this is the focus of this Report. We first give an overview of volcano plots and scaling relations. Deviations from scaling relations and the volcano plot and their causes are discussed in more detail. Finally, design strategies that do not rely on the volcano plot paradigm are reviewed. • Volcano plots are powerful tools in catalyst design. • Catalysts that conform to volcano plots have a limit to their performance. • There are many ways to deviate from the volcano plot and underlying scaling relations. • New design strategies have been developed to handle cases that do not obey volcano plots and scaling relations. [ABSTRACT FROM AUTHOR]

Catalytic dehydrogenation of ammonia borane is one of the most promising routes for the production of clean hydrogen as it is seen as a highly efficient and safe method. However, its large-scale industrial application is either limited by the high cost of the catalyst (usually a noble metal based catalyst) or by the low activity and poor reusability (usually a non-noble metal catalyst). In this study, we have successfully prepared three low-cost CuCo 2 O 4 nanocatalysts, namely: (i) Ti supported CuCo 2 O 4 film made of CuCo 2 O 4 nanoplates, (ii) Ti supported CuCo 2 O 4 film made of CuCo 2 O 4 nanosheets, and (iii) unsupported CuCo 2 O 4 nanoparticles. Among the three catalysts used for the hydrolytic dehydrogeneration of ammonia borane, the CuCo 2 O 4 nanoplate film exhibits the highest catalytic activity with a turnover frequency (TOF) of ∼44.0 mol hydrogen min −1 mol cat −1 . This is one of the largest TOF value for noble-metal-free catalysts ever reported in the literature. Moreover, the CuCo 2 O 4 nanoplate film almost keeps its original catalytic activity after eight cycles, indicative of its high stability and good reusability. Owing to its advantages, the CuCo 2 O 4 nanoplate film can be a promising catalyst for the hydrolytic dehydrogenation of ammonia borane, which may find important applications in the field of hydrogen energy. [ABSTRACT FROM AUTHOR]

Microorganisms play an essential role in sulfide removal. Alkaline absorption solution facilitates the sulfide's dissolution and oxidative degradation, so haloalkaliphile is a prospective source for environmental-friendly and cost-effective biodesulfurization. In this research, 484 sulfide oxidation genes were identified from the metagenomes of the soda-saline lakes and a haloalkaliphilic heterotrophic bacterium Halomonas salifodinae IM328 (=CGMCC 22183) was isolated from the same habitat as the host for expression of a representative sequence. The genetic manipulation was successfully achieved through the conjugation transformation method, and sulfide: quinone oxidoreductase gene (sqr) was expressed via pBBR1MCS derivative plasmid. Furthermore, a whole-cell catalyst system was developed by using the engineered strain that exhibited a higher rate of sulfide oxidation under the optimal alkaline pH of 9.0. The whole-cell catalyst could be recycled six times to maintain the sulfide oxidation rates from 41.451 to 80.216 µmol·min−1·g−1 dry cell mass. To summarize, a whole-cell catalyst system based on the engineered haloalkaliphilic bacterium is potentiated to be applied in the sulfide treatment at a reduced cost. [ABSTRACT FROM AUTHOR]