Xiangtong Meng

Rational design and fabrication of sulfur-doped porous graphene with enhanced performance as a counter electrode in dye-sensitized solar cells

Exploring cost-effective counter electrodes (CEs) with high electrocatalytic activity and excellent electrochemical stability is one of concerned issues for practicable applications of dye-sensitized solar cells (DSSCs). Graphene (G), featuring unique and intriguing physicochemical properties, has emerged as one of the most promising candidates. Nevertheless, the relationships between the electrochemical activity and the intrinsic structure of G need to be further understood. Herein, we report a facile yet effective strategy for engineering sulfur-doped porous graphene (SPG) using sulfur powder as the sulfur source and pore-forming agent. The as-made SPG as the CE for DSSCs achieves a high power conversion efficiency of 8.67%, which is superior to Pt (7.88%), and robust electrochemical stability. The influence of annealing temperature on SPG is analyzed, and SPG prepared at 900 °C shows the best photovoltaic and electrochemical performance. Both experimental and theoretical efforts first elucidate that highly exposed rich edge sites and interconnected porous channels, as well as low ionization energy derived from sulfur species within the G matrix play vital roles in enhanced reaction kinetics and triiodide reduction activity. The present work will inspire the construction of porous graphene with surface-enriched active sites and interconnected networks for advanced energy applications.

Nitrogen and phosphorus dual-doped graphene as a metal-free high-efficiency electrocatalyst for triiodide reduction

Alternative high-performance electrocatalysts for triiodide (I3-) reduction of low-cost dye-sensitized solar cells (DSSCs) are urgently sought after. To address the concerned issues, we report a facile strategy for engineering the nitrogen and phosphorus dual-doped graphene (NPG) via an efficient ball-milling process, followed by a simple thermal annealing approach utilizing melamine (C3H6N6) and triphenylphosphine ((C6H5)3P) as the N and P source, respectively. When employed as the counter electrode (CE) in DSSCs, such a metal-free material exhibits excellent electrocatalytic activity towards the I3-/I- redox reaction. Dual-doping of N and P heteroatoms can markedly enhance the photovoltaic performance of DSSCs by a synergistic effect and a high conversion efficiency of 8.57% is achieved, which is superior to Pt CE, and much higher than that of the single-component N- or P-doped graphene electrodes. In addition, the NPG CE also shows an outstanding electrochemical stability. The present results demonstrate that the NPG as a low-cost and high-efficiency electrocatalyst for reduction of I3- will be one of the promising CE materials in DSSCs.

CoS nanosheets-coupled graphene quantum dots architectures as a binder-free counter electrode for high-performance DSSCs

Hybrid materials with alternate components and synergetic effects are promising and intriguing materials as electrodes for high-performance energy storage/conversion devices. Cobalt sulphide (CoS) is one of the low-cost but inactive catalysts as counter electrode (CE) for dye-sensitized solar cells (DSSCs). How to optimize its structure and further enhance its electrochemical activity for I3− reduction remains a major challenge. Herein, a simple and efficient approach has been adopted to configure CoS sheets-coupled graphene quantum dots (GQDs) architectures via electrodepositing GQDs and CoS on the fl uorine doped tin oxide glass substrate. When employed as the binder-free CE for DSSCs, the as-made CoS-GQDs exhibits a high catalytic activity towards the reduction of I3−, evidenced by the results of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Tafel polarization measurements. A conversion efficiency of 7.30% is achieved, being superior to CoS CE (5.55%) and Pt CE (6.94%) due to their synergetic effects. The present work provides a simple method for configuring low-cost binder-free CE materials for replacing Pt.摘要染料敏化太阳能电池(DSSCs)因其造价低、稳定性高、工艺简单,备受关注. 廉价对电极材料的设计与构筑是亟需解决的关键科学问题之一. 本文采用电沉积技术, 在FTO玻璃基底上制备了硫化钴纳米片-石墨烯量子点复合结构纳米材料, 研究了其直接作为DSSCs电极材料的催化性能和光电转换效率. 结果发现, 该材料对I3−的还原表现出较高的催化性能, 光电转换效率达7.30%, 优于单一的硫化钴(5.55%)和商业化的贵金属铂催化剂(6.94%). 本研究为廉价、可取代铂的无粘结剂电极材料的开发提供了一个有效的途径.

Scrutinizing Defects and Defect Density of Selenium-Doped Graphene for High-Efficiency Triiodide Reduction in Dye-Sensitized Solar Cells

Understanding the impact of the defects/defect density of electrocatalysts on the activity in the triiodide (I3- ) reduction reaction of dye-sensitized solar cells (DSSCs) is indispensable for the design and construction of high-efficiency counter electrodes (CEs). Active-site-enriched selenium-doped graphene (SeG) was crafted by ball-milling followed by high-temperature annealing to yield abundant edge sites and fully activated basal planes. The density of defects within SeG can be tuned by adjusting the annealing temperature. The sample synthesized at an annealing temperature of 900 °C exhibited a superior response to the I3- reduction with a high conversion efficiency of 8.42 %, outperforming the Pt reference (7.88 %). Improved stability is also observed. DFT calculations showed the high catalytic activity of SeG over pure graphene is a result of the reduced ionization energy owing to incorporation of Se species, facilitating electron transfer at the electrode-electrolyte interface.