Molybdenum Phosphide Flakes Catalyze Hydrogen Generation in Acidic and Basic Solutions

Zhongzhong Chen,Zhibo Chen,Zhipeng Huang,Jie Wang,Cuncai Lv,Lihuang Jin

doi:10.4236/ajac.2014.517127

Abstract

Molybdenum phosphide (MoP) flakes were synthesized by the reduction of hexaammonium heptamolybdate tetrahydrate and ammonium dihydrogen phosphate. The flakes are porous and constructed by MoP nanoparticles with ca. 100 nm diameters. The lateral size of flakes ranges from less than 1 μm to larger than 5 μm, and the thickness of MoP fakes is ca. 200 nm. The mixture of MoP flakes and carbon black exhibits effective catalytic activity in the hydrogen evolution reaction. The optimal overpotential required for 20 mA·cm﹣2 current density is 155 mV in acidic solution and 184 mV in basic solution. The mixture can work stably in long-term hydrogen generation in both acidic and basic solution. The faradaic yield of mixture in hydrogen evolution reaction is nearly 100% in both acidic and basic solution. The Mo and P species in MoP flakes are found to have small positive and negative charge, respectively. The catalytic activity of MoP flakes is likely to be correlated with this charged nature.

Highlights

As a clean and renewable resource, hydrogen is believed to be one of the most promising alternative energy carriers [1] [2]
We found that Molybdenum phosphide (MoP) flakes show efficient catalytic activity in hydrogen evolution reaction (HER) in both acidic and basic solution, and the corresponding overpotential required for 20 mA∙cm−2 current density is 155 mV in acidic solution and 184 mV in basic solution, respectively
The optimal η20 of MoP flakes mixed with carbon black is as small as 155 mV in acidic solution and 184 mV in basic solution

Summary

Introduction

As a clean and renewable resource, hydrogen is believed to be one of the most promising alternative energy carriers [1] [2]. Effective electrocatalysts for HER are essential for efficient hydrogen generation from electro-. (2014) Molybdenum Phosphide Flakes Catalyze Hydrogen Generation in Acidic and Basic Solutions. Though platinum-group metals have shown excellent catalytic activity in HER, their widespread commercial application is inhibited by high cost and low abundance. The successful demonstration of catalytic activity of Ni2P inspires research concerning the application of metal phosphide in hydrogen generation (e.g., Ni12P5 [21], and CoP [22] [23]). The catalytic activity of MoP flakes in HER is demonstrated. We found that MoP flakes show efficient catalytic activity in HER in both acidic and basic solution, and the corresponding overpotential required for 20 mA∙cm−2 current density is 155 mV in acidic solution and 184 mV in basic solution, respectively. Potentiostatic electrolysis and accelerated degradation experiments demonstrate the long-term stability of MoP flakes in hydrogen generation in acidic and basic solution. Mo and P in MoP flakes were found to have slight charge, and the catalytic activity of MoP might be correlated with these features

Synthesis of MoP Flakes

Characterization

Electrochemical Measurement

Results and Discussion

Conclusion