Study On The Preparation And Performance Of MoP-based Electrocatalysts For Hydrogen Evolution Reaction

The increasing depletion of fossil fuels raises worldwide concerns on energy crisis and environment. In recent years, hydrogen has been vigorously pursued as clean and sustainable energy for replacing fossil fuels in 21 st century. Importantly, the required electricity for electrochemical water-splitting can be simply generated from renewable energy, such as wind, tide, and solar energy. Thus, electrochemical water-splitting has attracted considerable attention due to its environmentally benign feature. Electrocatalyst plays vital role in this process as it is highly necessary to drive hydrogen evolution reaction(HER) with high current density and low overpotential. Although Pt-based metals are regarded as the best HER electrocatalysts currently, the scarcity and high cost impede their wide usage. Therefore, searching for a low-cost and earth-abundant substitute for Pt-based electrocatalysts is a prerequisite for the application of this technology in large scale. Moreover, high performance, good durability and easy fabrication are substantially preferable for developing novel electrocatalysts used in practical applications.Here, we mainly report the strategies of controlling structure and morphology of molybdenum phosphide(MoP) to improve its catalytic performance. Firstly, we prepared a three-dimensional molybdenum phosphide(3D MoP) as a non-precious-metal electrocatalyst for hydrogen evolution reaction(HER) by using cheap sponge(polyurethane, PU) as sacrificed template in temperature-programmed reduction(TPR) method. The obtained 3D MoP not only has high large surface area, but also possesses porous and channel-rich structure, which the sidewall of the pore is comprised of refined nanoparticles. The 3D MoP sponge was used as a bulky and bind-free HER electrode and exhibited excellent catalytic activity in acidic electrolyte(achieving 10 and 20 mA cm-2 at overpotential of 105 and 155 mV, respectively). In addition, this novel bulky HER electrode showed a relatively small Tafel slope of 126 mV dec-1, a high exchange current density of 3.052 mA cm-2, and the Faradaic efficiency of nearly 100 %. Furthermore, this bulky electrode revealed high tolerance and durability both in acid and basic condition, maintaining 96% and 93% of its initial catalytic activity after continuous tests for 60000 s. Hence, our work paves a feasible way of fabricating cheap and highly efficient HER electrode in large-scale for electrochemical water-splitting technology.Also, we prepared MoP hemisphere with large surface area directly grown on Carbon Cloth(CC) to act as an active integrated 3D MoP hydrogen evolution cathode by combining hydrothemal method with TPR. The obtained electrocatalyst 3D MoP-HS@CC as a bind-free electrode reveals surperior HER performance and decent durability in both acidic and basic media. In acid solution, it exhibits a low onset overpotential of 30 mV, a small Tafel slope of 61 mV dec-1, and a large exchange current density of 0.438 mA cm-2. In order to afford current densities of 10 and 100 mA cm-2, the overpotentials only need 87 and 195 mV, respectively. Furthermore, it exhibits an onset overpotential of 33 mV and a Tafel slope of 64 mV dec-1 in alkaline solution. To attain current densities of 10 and 100 mA cm-2, the overpotential of electrode needs to arrive at 121 and 223 mV, respectively. Experimental results also show that the density of MoP hemispheres on the surface of CC can be controlled by tuning the synthetic conditions. Therefore, the MoP-HS@CC provides us an efficient and economical 3D cathode toward electrochemical water-splitting.In a word, this thesis provides new strategies on constructing three-dimensional efficient electrocatalyst, which paves a way to practical use for electrochemical water-splitting technology.