Wenwen Zha,Qiushi Ruan,Lingqiao Kong,Xufeng Xi,Muhammad Ali Turgunov,Wei Zhang,Kun Chang,ZhengMing Sun
Graphitic carbon nitride is a benchmark n-type polymer photocatalyst for hydrogen evolution from water in suspension systems, though it is extremely inefficient in photoelectrochemical (PEC) systems. Minimizing the considerable discrepancy between the two systems is challenging but necessary for applications. Efficient electron collection on the catalyst surface is key to carbon nitride’s photocatalytic hydrogen evolution performance in suspension systems, but it is rarely achieved in PEC films because of the electron transfer barrier from bulk to the surface. Here, we report a hydrogel-based PEC photocathode that inherits the intrinsic advantages of suspension systems, providing a suspension-like environment for carbon nitride hydrogen evolution. This promotes electron trapping at heteroatom-induced shallow surface trap states, mitigates space charge layer, and reduces charge migration distance in hydrogel-supported heteroatoms-doped carbon nitride nanosheets, enabling efficient electron collection on the surface, leading to 10-time improvement in photocathodic performance. This study provides proof of concept for mimicking suspension in photoelectrodes that can be applied to various powder-based photoelectrochemical cells.
Fu Ruijie,Yao Kai,Zhang Qisheng,Jia Dongying,Zhao Jiayuan,Chi Yuanlong
A series of collagen hydrolysates (CHs) were prepared from pigskin shavings by using pepsin (PCH), trypsin (TCH), Alcalase (ACH), HCl (HCH), and NaOH (NCH). Their physicochemical properties, including degree of collagen hydrolysis, molecular weight distribution, electric charge, and microstructure, were investigated, and their flocculation performance was evaluated in a kaolin suspension, at varied pHs and concentrations. PCH exhibited high flocculation capability under acidic and neutral conditions, and its efficiency for removing suspended particles was approximately 80% at a concentration of 0.05 g/L. TCH, ACH, HCH, and NCH showed almost no flocculation capability. The flocculation capability of PCH could be mainly due to a combination of optimal molecular weight distribution and electric charge. This study could provide an environment-friendly natural flocculant and also proposes a promising approach for the reuse of collagen wastes.
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In this study, a natural polymer-based organic flocculant (sodium alginate-methacrylatoethyl trimethyl ammonium chloride, SA-PDMC) was synthesized by graft copolymerization. The optimum preparation procedures were determined by single factor experiments. The flocculation behaviors of SA-PDMC were investigated in humic acid (HA) and kaolin suspension considering the effects of flocculant doses and initial pH. The results indicated that charge neutralization and bridging action played an important role in the removals of HA and kaolin. Also, SA-PDMC performed well in a wide pH range of 5.0−10.0. Besides, SA-PDMC, as polyaluminium (PAC) aid, was investigated in the lake water treatment. The ratio of PAC and SA-PDMC was optimized through response surface methodology based on a central composite design. Results showed that SA-PDMC and PAC have a strong synergy, under optimal conditions SA-PDMC can reduce the dose of PAC by 40 % while ensuring the water quality.
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