Enhancing Hydrogen\nEvolution Reaction through the\nImproved Mass Transfer and Charge Transfer by Bimetal Nodes

The high cost of hydrogen production by water electrolysis\nseverely\nchallenges its commercial application. It is highly desirable to develop\nefficient electrocatalysts and innovative electrolytic cells. Introducing\nadditional metal nodes to form bimetallic metal–organic framework\n(MOF) is a simple, feasible strategy to overcome the poor electrocatalytic\nperformance of single-metal MOF. In this study, the hydrothermal method\nis used to synthesize bimetallic Ni<i><sub>x</sub></i>Co<sub>y</sub>-BTC. It is found that for hydrogen evolution reaction (HER),\nNi<sub>0.8</sub>Co<sub>0.2</sub>-BTC merely requires a potential of\n−0.203 V (vs reverse hydrogen electrode, RHE) to achieve 10\nmA cm<sup>–2</sup>, which is significantly lower than that\nof Ni-BTC (−0.341 V vs RHE). Notably, electrochemical impedance\nspectroscopy (EIS) and distribution of relaxation time (DRT) analysis\nindicate that Ni<i><sub>x</sub></i>Co<i><sub>y</sub></i>-BTC has improved charge transfer and mass transfer process,\ncompared with Ni-BTC. Electron paramagnetic resonance (EPR) confirms\nthat Ni<sub>0.8</sub>Co<sub>0.2</sub>-BTC has more unpaired electrons\nthan Ni-BTC. Density functional theory (DFT) calculations show that\ncompared with Ni-BTC, Ni<i><sub>x</sub></i>Co<i><sub>y</sub></i>-BTC is more thermodynamically favorable for the\nadsorption of H<sup>+</sup>, OH<sup>–</sup>, and H<sub>2</sub>O. It demonstrates that the change of mass transfer caused by bimetallic\nnodes and the delicate variation of MOF surface play an important\nrole in the electrochemical process. Moreover, a novel electrolytic\ncell was developed using a methanol oxidation reaction (MOR) to replace\noxygen evolution reaction (OER). In this MOR-based electrolytic cell,\na current density of 50 mA cm<sup>–2</sup> can be achieved\nat only a cell voltage of 1.85 V, which is lower than the 2.22 V of\nOER-based electrolytic cell, suggesting that 16.7% electric energy\ncan be saved. At the same time, the Faraday efficiency (FE, 98.2%)\nof the MOR-based cell is higher than that (94.5%) of the OER-based\ncell. This research offers a promising strategy for low-cost hydrogen\nproduction.