On-Chip Microdevice Unveils Reactant Enrichment Effect Dominated Electrocatalysis Activity in Molecular-Linked Catalysts

Abstract

Molecular functionalization has been intensely studied and artificially constructed to advance various electrocatalytic processes. While there is a widely approved charge-doping effect, the underlying action for reactant distribution/transport remains long neglected. Here an on-chip microdevice unravels that the proton enrichment effect at prototypical methylene blue (MB)/MoS2 interfaces rather than charge doping contributes to the hydrogen evolution reaction (HER) activity. Back-gated electrical/electrochemical tests detect quantitatively a strong charge injection from MB to MoS2 realized over diploid carrier density, but these excess carriers are unqualified for the actual enhanced HER activity (from 32 to 125 mA cm–2 at −0.29 V). On-chip electrochemical impedance further certifies that the proton enrichment in the vicinity of MoS2, which is generated by the nucleophilic group of MB, actually dominates the HER activity. This finding uncovers the leading function of molecular-linked catalysts.

Four-Terminal Electrochemistry: A Back-Gate Controls the Electrochemical Potential of a 2D Working Electrode

“…This allowed us to achieve up to a 30-fold increase in the electron transfer rate to outer-sphere redox couples from a 5 nm ZnO back-gated electrode at V G values less than 8 V, for example . Collectively, these early demonstrations, and those of others, − have encouraged us to continue exploring the utility of back-gated 2D working electrodes for enhancing electrochemical reaction rates.…”

Interface Engineering of a Hierarchical P-Modified Co/Ni3P Heterostructure for Highly Efficient Water Electrolysis Coupled with Hydrazine Degradation

“…Hydrogen (H 2 ), as a zero-carbon energy carrier, plays an important role in solving the growing energy crisis and environmental issues. – The electrocatalytic water spitting to gain hydrogen has been regarded as an energy-saving and environmentally friendly strategy. – Generally, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are typical two half-reactions of water electrolysis. – For the OER with slow kinetics, many research efforts have been carried out to achieve important progress. – Among them has been the use of anode small-molecule (alcohol, urea, furfural, glucose, and hydrazine hydrate) oxidation reaction to replace the traditional OER, which has the lower voltage advantage to assist the energy-saving hydrogen production from water electrolysis. – Lowest theoretical potential (−0.33 V vs RHE) is the unique feature of the hydrazine oxidation reaction (HzOR), which proves to be a thermodynamically more favorable way compared to the OER (1.23 V vs RHE). – Some pioneering research works have gained inspiring progress based on the development of noble metals (Pt and Pd) or nonprecious metals (Ni, Co, Cu, and Fe) for the HzOR-assisted H 2 generation. – However, the exploitation of highly active and stable electrodes for large-scale energy-saving H 2 production still remains challenging.…”

Interlayer Delocalized Electrons Activate Basal Plane for Ultrahigh-Current-Density Hydrogen Evolution

“…5−8 Therefore, numerous follow-up studies are focused on enhancing the conductivity of TMDCs in order to achieve efficient charge transfer at basal plane sites. 9−13 Some typical strategies, such as phase engineering, 10,14 electrical contact engineering, 11,12 and surface modification, 15,16 have been exploited to achieve high conductivity and electrocatalytic activity. However, in the case of layer-dependent catalysts, electrons tend to conduct along the two-dimensional plane, while the vertical direction is often prohibited due to the huge energy barrier in the vdW gap.…”

“…Two-dimensional transition metal dichalcogenides (TMDCs) with glorious hydrogen evolution reaction (HER) performance have emerged as a viable alternative to noble metals for advancing green hydrogen energy. − However, a substantial proportion of basal planes exhibit relatively low activity toward the HER due to their lower conductivity and consequently less efficient charge transfer kinetics, significantly constraining the overall performance. − Therefore, numerous follow-up studies are focused on enhancing the conductivity of TMDCs in order to achieve efficient charge transfer at basal plane sites. − Some typical strategies, such as phase engineering, , electrical contact engineering, , and surface modification, , have been exploited to achieve high conductivity and electrocatalytic activity. However, in the case of layer-dependent catalysts, electrons tend to conduct along the two-dimensional plane, while the vertical direction is often prohibited due to the huge energy barrier in the vdW gap.…”