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A mechanochemical approach through ball milling (BM) to produce NiO clusters supported on TiO 2 has been successfully applied, resulting in a NiO/TiO 2 p-n heterojunction as an efficient and sunlight-sensitive photocatalyst. Besides, the synergistic interaction between NiO and TiO 2 (P90) enhances charge separation, ultimately boosting the H 2 photoproduction. Notably, the material obtained by BM, denoted as NiO/P90-BM achieved an H 2 evolution rate that was over 12 times higher than that of Neat P90 (8.85 mmol h−1 g−1 vs. 0.73 mmol h−1 g−1). The predominance of the high-spin configuration for Ni2+ in NiO was ascribed as one of the main reasons for such performance. Additionally, photoelectrochemical measurements revealed that NiO addition was beneficial for the photoelectrochemical properties. The NiO/P90-BM exhibited the lowest charge transfer resistance, the highest photocurrent signal, and the highest electronic density. Furthermore, the achieved H 2 evolution rate is on par with that of materials produced using noble metals and energy-intensive approaches. Noticeably, cycling, long-term, and aging tests have shown that the reported photocatalyst is efficient after several cycles, prolonged use, and after long periods of storage. [Display omitted] • One-step ball milling process led to a NiO/TiO 2 p-n heterojunction. • The addition of NiO boosted sunlight absorption. • This noble metal-free photocatalyst exhibited an outstanding H 2 evolution rate. • High-spin of Ni2+ in NiO was crucial for such outstanding performance. • NiO/P90-BM performs comparably to noble metal-based and energy-intensive materials. [ABSTRACT FROM AUTHOR]

The present work reports the development of a new analytical method for the determination of free glycerol in biodiesel samples using enzymatic-spectrophotometric assay combined with solid phase extraction (SPE) by molecularly imprinted poly(methacrylic acid) (MIP). The spectrophotometric method was performed using a commercial enzyme kit. The enzymatic-spectrophotometric method showed good analytical performance in terms of the linearity (0.998), limit of detection (7.70 × 10−6% w/w), limit of quantification (2.54 × 10−5% w/w), repeatability (0.42% to 7.91%), and recovery (99.4% to 112%). The analyses of several biodiesel samples by SPE and enzymatic-spectrophotometric method provided recovery values between 91.4% and 105%. Therefore, the high selectivity of molecularly imprinted polymer (MIP) was successfully applied to isolate free glycerol from biodiesel samples containing acylglycerols and methyl esters, and thereby allow enzymatic-spectrophometric based quantification. The developed method using SPE with MIP was efficient for the determination of free glycerol in biodiesel and the obtained results are in agreement with gas chromatrography (GC) that was used as a reference protocol. [ABSTRACT FROM AUTHOR]