Direct Synthesis of Molybdenum Phosphide Nanorods on Silicon Using Graphene at the Heterointerface for Efficient Photoelectrochemical Water Reduction

Transition metal phosphides(TMPs)and transition metal dichalcogenides(TMDs)have been widely investigated as photoelectrochemical(PEC)catalysts for hydrogen evolution reaction(HER).Using high-temperature processes to get crystallized compounds with large-area uniformity,it is still challenging to directly synthesize these catalysts on silicon photocathodes due to chemical incompatibility at the heterointerface.Here,a graphene interlayer is applied between p-Si and MoP nanorods to enable fully engineered interfaces without forming a metallic secondary compound that absorbs a parasitic light and provides an inefficient electron path for hydrogen evolution.Furthermore,the graphene facilitates the photogenerated electrons to rapidly transfer by creating Mo-O-C covalent bondings and energetically favorable band bending.With a bridging role of graphene,numerous active sites and anti-reflectance of MoP nanorods lead to significantly improved PEC-HER performance with a high photocurrent density of 21.8 mA cm−2 at 0 V versus RHE and high stability.Besides,low dependence on pH and temperature is observed with MoP nanorods incorporated photocathodes,which is desirable for practical use as a part of PEC cells.These results indicate that the direct synthesis of TMPs and TMDs enabled by graphene interlayer is a new promising way to fabricate Si-based photocathodes with high-quality interfaces and superior HER performance.

Rationally designed graphene channels for real-time sodium ion detection for electronic tongue

Monitoring taste-inducing ions and molecules continuously in liquids or solutions is of great considerable matter for the realization of the electronic tongue(E-tongue).Particularly from the five major tastes,the highly selective,sensitive detection of Na^(+)in real-time is prioritized.Prioritization is due to the saltiness of food is the key ingredient in most meals.Nevertheless,existing Na^(+)detecting devices have relatively low performances of selectivity,sensitivity,and lack of on–off functions.Additionally,conventional devices significantly deteriorate in capac-ity due to repetitive usage or lifetime shortage by degradation of the sensing mate-rial.Herein,a graphene-based channel was rationally designed by the facile decoration of Calix[4]arene and Nafion to address this issue.They act as a receptor and a molecular sieve,respectively,to enhance selectivity and sensitivity and elon-gate the life expectancy of the device.This device was merged with a microfluidic channel to control the injection and withdrawal of solutions to fulfill dynamic on–off functions.The fabricated device has highly selective,sensitive Na^(+)detection properties compared to other 10 molecule/ionic species.Dynamic on–off functions of the device were available,also possesses a long lifespan of at least 220 days.Additionally,it can precisely discriminate real beverages containing Na^(+),which can be observed by principal component analysis plot.These features offer the possibility of ascending to a platform for E-tongues in near future.