Limits...
Enhanced hydrogen evolution reaction on hybrids of cobalt phosphide and molybdenum phosphide

View Article: PubMed Central - PubMed

ABSTRACT

Production of hydrogen from water electrolysis has stimulated the search of sustainable electrocatalysts as possible alternatives. Recently, cobalt phosphide (CoP) and molybdenum phosphide (MoP) received great attention owing to their superior catalytic activity and stability towards the hydrogen evolution reaction (HER) which rivals platinum catalysts. In this study, we synthesize and study a series of catalysts based on hybrids of CoP and MoP with different Co/Mo ratio. The HER activity shows a volcano shape and reaches a maximum for Co/Mo = 1. Tafel analysis indicates a change in the dominating step of Volmer–Hyrovský mechanism. Interestingly, X-ray diffraction patterns confirmed a major ternary interstitial hexagonal CoMoP2 crystal phase is formed which enhances the electrochemical activity.

No MeSH data available.


Related in: MedlinePlus

(a) HER polarization curves of Co0.5Mo0.5P electrode before and after potential sweeps (–0.5 ∼ +0.1 V versus RHE) for 1000 cycles in 0.1 M HClO4 solution (scan rate 2 mV s−1) (b). Time dependence of the quantity of hydrogen produced experimentally (dashed line) and the Faradaic efficiency of the Co0.5Mo0.5P catalyst at a fixed cathodic current density of 10 mA cm−2 in 0.1 M HClO4 solution 60 min.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5383849&req=5

RSOS161016F7: (a) HER polarization curves of Co0.5Mo0.5P electrode before and after potential sweeps (–0.5 ∼ +0.1 V versus RHE) for 1000 cycles in 0.1 M HClO4 solution (scan rate 2 mV s−1) (b). Time dependence of the quantity of hydrogen produced experimentally (dashed line) and the Faradaic efficiency of the Co0.5Mo0.5P catalyst at a fixed cathodic current density of 10 mA cm−2 in 0.1 M HClO4 solution 60 min.

Mentions: To assess the stability of the Co0.5Mo0.5P electrodes, we performed the accelerated deterioration experiment by sweeping the applied potential from −0.5 to + 0.2 V versus RHE in 0.1 M HClO4 solution. After 1000 cycles on the Co0.5Mo0.5P electrode, only a slight shift (11 mV increase in η10) in the polarization curve is observed as shown in figure 7a, indicating a good stability of the Co0.5Mo0.5P catalyst in the operating conditions. Faradaic efficiency was determined by performing a controlled potential electrolysis experiment using an H-type cell. The amount of hydrogen gas produced was calculated from the volume of gas at a fixed cathodic current density of 10 mA cm−2 in 0.1 M HClO4 solution for 60 min. The experimentally determined hydrogen quantity was compared to the calculated amount based on the charge consumed as shown in figure 7b. The Faradaic efficiency reached 98% after 60 min of operation. The cathodic current density recorded for driving the HER at overpotential of 165 mV as a function of time is plotted in the electronic supplementary material, figure S8. The current density slightly decreased about 5% after 6 h of electrolysis. These results imply that the Co0.5Mo0.5P catalyst is a highly efficient and cathodically stable HER catalyst in the acidic environment.


Enhanced hydrogen evolution reaction on hybrids of cobalt phosphide and molybdenum phosphide
(a) HER polarization curves of Co0.5Mo0.5P electrode before and after potential sweeps (–0.5 ∼ +0.1 V versus RHE) for 1000 cycles in 0.1 M HClO4 solution (scan rate 2 mV s−1) (b). Time dependence of the quantity of hydrogen produced experimentally (dashed line) and the Faradaic efficiency of the Co0.5Mo0.5P catalyst at a fixed cathodic current density of 10 mA cm−2 in 0.1 M HClO4 solution 60 min.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383849&req=5

RSOS161016F7: (a) HER polarization curves of Co0.5Mo0.5P electrode before and after potential sweeps (–0.5 ∼ +0.1 V versus RHE) for 1000 cycles in 0.1 M HClO4 solution (scan rate 2 mV s−1) (b). Time dependence of the quantity of hydrogen produced experimentally (dashed line) and the Faradaic efficiency of the Co0.5Mo0.5P catalyst at a fixed cathodic current density of 10 mA cm−2 in 0.1 M HClO4 solution 60 min.
Mentions: To assess the stability of the Co0.5Mo0.5P electrodes, we performed the accelerated deterioration experiment by sweeping the applied potential from −0.5 to + 0.2 V versus RHE in 0.1 M HClO4 solution. After 1000 cycles on the Co0.5Mo0.5P electrode, only a slight shift (11 mV increase in η10) in the polarization curve is observed as shown in figure 7a, indicating a good stability of the Co0.5Mo0.5P catalyst in the operating conditions. Faradaic efficiency was determined by performing a controlled potential electrolysis experiment using an H-type cell. The amount of hydrogen gas produced was calculated from the volume of gas at a fixed cathodic current density of 10 mA cm−2 in 0.1 M HClO4 solution for 60 min. The experimentally determined hydrogen quantity was compared to the calculated amount based on the charge consumed as shown in figure 7b. The Faradaic efficiency reached 98% after 60 min of operation. The cathodic current density recorded for driving the HER at overpotential of 165 mV as a function of time is plotted in the electronic supplementary material, figure S8. The current density slightly decreased about 5% after 6 h of electrolysis. These results imply that the Co0.5Mo0.5P catalyst is a highly efficient and cathodically stable HER catalyst in the acidic environment.

View Article: PubMed Central - PubMed

ABSTRACT

Production of hydrogen from water electrolysis has stimulated the search of sustainable electrocatalysts as possible alternatives. Recently, cobalt phosphide (CoP) and molybdenum phosphide (MoP) received great attention owing to their superior catalytic activity and stability towards the hydrogen evolution reaction (HER) which rivals platinum catalysts. In this study, we synthesize and study a series of catalysts based on hybrids of CoP and MoP with different Co/Mo ratio. The HER activity shows a volcano shape and reaches a maximum for Co/Mo = 1. Tafel analysis indicates a change in the dominating step of Volmer–Hyrovský mechanism. Interestingly, X-ray diffraction patterns confirmed a major ternary interstitial hexagonal CoMoP2 crystal phase is formed which enhances the electrochemical activity.

No MeSH data available.


Related in: MedlinePlus