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Developing efficient water splitting electrocatalysts plays a critical role in lowering the energy cost for hydrogen production, which requires accurate evaluation of the catalytic performance especially under industrially relevant conditions. In this work, we design a two-chamber electrolyzer testing system simulating practical water electrolyzer system to enable catalytic performance evaluation under industrially relevant conditions. A one-step electrodeposition method is used to synthesize binary and ternary Ni alloy HER catalysts and the catalytic electrodes are screened and optimized with the two-chamber electrolyzer testing system. A voltage of 1.64 V without iR compensation at a current density of 200 mA/cm2 is obtained with continuous operation for 70 h. Different HER activity trend is observed from conventional three-electrode experiments with low-concentration alkaline electrolytes at room temperature and the two-chamber electrolyzer measurements, further supporting the importance of catalytic performance evaluation under industrially relevant conditions. The electrodeposition synthesis method is further used to prepare large-area catalytic electrodes over 400 cm2 with good uniformity. • Ni-alloy HER catalysts are characterized under industrially relevant conditions with a home-build electrolyzer system. • Electrolyzer with an electrodeposited NiMo HER catalyst exhibits a remarkably low voltage of 1.64 V at 200 mA/cm2. • Different activity trends of HER catalysts are observed under industrially relevant conditions and three-electrode tests. • Ni-alloy catalysts with an active area over 400 cm2 are successfully synthesized with excellent performance uniformity. [ABSTRACT FROM AUTHOR]

Phenylalanine, as an essential aromatic amino acid, is not only needed for protein and vital molecules such as neurotransmitter and hormone synthesis but also a substrate for the biosynthesis of phenylpropanoids and various bioactive compounds. The metabolism of phenylalanine is dynamic and transitory, which would otherwise inhibit cell growth. Therefore, it is challenging and imperative to monitor intracellular phenylalanine bioavailability in real time, which has great significance for evaluating the effectiveness of introducing pathway-specific genetic modifications to enhance phenylalanine generation. In this study, we proposed a live-cell biomonitoring system to assess phenylalanine bioavailability in real time in cyanobacteria based on codon degeneracy and species-specific usage bias. The biomonitoring system was generated through genetic modification of phenylalanine codons in the chloramphenicol antibiotic resistance gene to wholly preferred and rare codons, in combination with an orthogonal constitutive promoter Trc to express these genes. Cyanobacterial cells equipped with a preferred codon-based gene showed a significant growth advantage over those with rare codons under antibiotic pressure, while the delayed growth caused by rare codon-based genes could be rescued by supplementing phenylalanine in the cultivation medium. Increasing intracellular phenylalanine bioavailability could promote rare codon-based gene containing cell growth to a similar level as wild-type strains harboring preferred codon-based gene, providing a live-cell visualized screening method to relatively define phenylalanine content from either random mutation libraries or pathway-specific engineering cyanobacterial chassis before conducting labor-intensive quantitative measurements. [Display omitted] [ABSTRACT FROM AUTHOR]