Abstract
Efficient water electrolyzers are constrained by the lack of low-cost and earth-abundant hydrogen evolution reaction (HER) catalysts that can operate at industry-level conditions and be prepared with a facile process. Here we report a self-standing MoC–Mo2C catalytic electrode prepared via a one-step electro-carbiding approach using CO2 as the feedstock. The outstanding HER performances of the MoC–Mo2C electrode with low overpotentials at 500 mA cm−2 in both acidic (256 mV) and alkaline electrolytes (292 mV), long-lasting lifetime of over 2400 h (100 d), and high-temperature performance (70 oC) are due to the self-standing hydrophilic porous surface, intrinsic mechanical strength and self-grown MoC (001)–Mo2C (101) heterojunctions that have a ΔGH* value of −0.13 eV in acidic condition, and the energy barrier of 1.15 eV for water dissociation in alkaline solution. The preparation of a large electrode (3 cm × 11.5 cm) demonstrates the possibility of scaling up this process to prepare various carbide electrodes with rationally designed structures, tunable compositions, and favorable properties.
Highlights
Efficient water electrolyzers are constrained by the lack of low-cost and earth-abundant hydrogen evolution reaction (HER) catalysts that can operate at industry-level conditions and be prepared with a facile process
A self-standing MoS2/Mo2C electrode grown on a titanium (Ti) foil by a chemical vapor deposition method (CVD) showed excellent HER performance at 1000 mA cm−2 and a long lifetime of over 1000 h in both acidic and alkaline solutions[20]
The first step is the electrochemical reduction of CO32- at the cathode, generating carbon while releasing O2- that is partly consumed by the carbonization of CO2 to replenish CO32- and partly discharging at the anode to generate O2
Summary
Efficient water electrolyzers are constrained by the lack of low-cost and earth-abundant hydrogen evolution reaction (HER) catalysts that can operate at industry-level conditions and be prepared with a facile process. The outstanding HER performances of the MoC–Mo2C electrode with low overpotentials at 500 mA cm−2 in both acidic (256 mV) and alkaline electrolytes (292 mV), long-lasting lifetime of over 2400 h (100 d), and high-temperature performance (70 oC) are due to the self-standing hydrophilic porous surface, intrinsic mechanical strength and self-grown MoC (001)–Mo2C (101) heterojunctions that have a ΔGH* value of −0.13 eV in acidic condition, and the energy barrier of 1.15 eV for water dissociation in alkaline solution. It is important to explore novel methods to prepare molybdenum carbides with enhanced robustness, high catalytic activity, long-lasting lifetime, and superior stability at high current densities (400–600 mA cm−2) and high operating temperatures (~70 oC) like the industrial water electrolyzer. Most synthesized catalyst layers cannot withstand a high current density and operate for a long-lasting lifetime because of the weak interfacial adhesion on the electrode substrate, and a robust self-standing MoC–Mo2C composite catalyst layer has not been achieved yet
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