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Interfaces Decrease the Alkaline Hydrogen-Evolution Kinetics Energy Barrier on NiCoP/Ti 3 C 2 T x MXene.

Hua-Jie NiuYu YanSiSi JiangTong LiuTong SunWei ZhouLin GuoJinghong Li
Published in: ACS nano (2022)
Heterointerfaces can adjust the adsorption energy with intermediates in the transition state for a much decreased kinetics energy barrier ( E a ). One typical transition metal phosphide, NiCoP grains (∼5 nm in size), was anchored on a Ti 3 C 2 T x MXene monolayer (∼1 nm in thickness) to boost the kinetics toward alkaline hydrogen evolution reaction (HER). General electrochemical experiments at different temperatures give a small E a of 31.4 kJ mol -1 , showing a 22.1% decrease compared to its counterpart NiCoP nanoparticles (40.3 kJ mol -1 ). Impressively, the overpotential of NiCoP@MXene dramatically decreases from 71 mV to 4 mV at 10 mA cm -2 when the temperature increases from 25 °C to 65 °C. On a single NiCoP@MXene sheet, scanning electrochemical microscopy (SECM) tests also give a very close value of E a = 31.9 kJ mol -1 , with a relative error of ∼1.6%. Density functional theory (DFT) calculations confirm the interface between NiCoP and MXene can effectively decrease the energy barrier of water dissociation by 16.0%. The three kinds of studies on macro, micro/nano, and atomic scales disclose the interfaces can reduce the kinetics energy barrier about 16.0-22.1%. Besides, the photothermal effect of MXenes can easily raise the catalyst temperature under vis-NIR light, which has been applied in practical scenarios under sunlight for energy savings.
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