Molybdenum Phosphide As A Cocatalyst For Photocatalytic Hydrogen Production By Dye Sensitized Under Visible Light

Nowadays,the global energy crisis and environmental pollution have become more and more serious,so it is urgent to develop and utilize renewable new energy sources.Hydrogen energy is a clean and renewable new energy,and dye-sensitized is a kind of common hydrogen production method.In order to achieve efficient dye-sensitized hydrogen production activity,a cocatalyst is needed.Among them,Mo P is an efficient cocatalyst.In this paper,Mo P was prepared by simple low-temperature calcination and used as a dye sensitizing hydrogen evolution cocatalyst,and its dye-sensitized photocatalytic activity for hydrogen generation was improved by compositing with g-C₃N₄and oxidative etching.The paper is consists of the following three parts:?1?The effects of different preparation temperatures on the crystallinity,particle size,specific surface area,electrical resistance,composition and catalytic activity of Mo P were investigated.Studies have shown that using EY as a sensitizer,trimethylamine as an electron donor,Mo P prepared at 400?shows the highest hydrogen production activity?about 155?mol/h?and better stability under visible light.The apparent quantum efficiency is 48%at 420 nm.The higher photocatalytic activity and stability can be attributed to its better crystallinity,higher Mo P content and the most efficient electron transfer rate.?2?Mo P/g-C₃N₄was prepared by physical milling and low-temperature heat treatment of Mo P and g-C₃N₄.The results show that the activity of sensitized hydrogen production is significantly improved after Mo P loading.The activity of EY-5 wt%Mo P/g-C₃N₄was more than 2 times compared with that of EY-Mo P?without g-C₃N₄?and more than 160 times compared with that of 5 wt%Mo P/g-C₃N₄?without sensitization?.The increase of the activity can be attributed to the increase in the absorption of visible light and the efficient electron transfer among EY,Mo P and g-C₃N₄.?3?The dissolved oxygen in the dilute Na OH solution is used to perform simple and controllable crystal surface etching on the Mo P,and oxygen is always ensured during the etching process.We have found that the oxygen dissolved in Na OH solution is selective etching for Mo P crystal faces.Compared to the?100?crystal plane,the etching of?001?crystal plane is more quick and easier because the?001?crystal plane of Mo P has higher surface energy,while the surface energy of?100?crystal plane is relatively low,so the etching is slower.After etching,the crystallite sizes of?001?and?100?face of Mo P decrease,and the specific surface area increases,which results in the increase of the adsorption of EY on the surface of the catalyst.This is a key factor to increase the photocatalytic hydrogen production activity.The hydrogen production activity of Mo P after alkaline etching for 12 h was increased by70%compared with that before caustic washing.With alkaline washing in the nitrogen atmosphere,its activity remained almost unchanged.