Integrating Hydrogen Production with Aqueous Selective Semi‐Dehydrogenation of Tetrahydroisoquinolines over a Ni₂P Bifunctional Electrode

Abstract

Exploring an alternative anodic reaction to produce value-added chemicals with high selectivity,e specially integrated with promoted hydrogen generation, is desirable. Herein, as elective semi-dehydrogenation of tetrahydroisoquinolines (THIQs) is demonstrated to replace the oxygen evolution reaction (OER) for boosting H 2 evolution reaction (HER) in water over aN i 2 Pn anosheet electrode.T he valueadded semi-dehydrogenation products,d ihydroisoquinolines (DHIQs), can be selectively obtained with high yields at the anode.The controllable semi-dehydrogenation is attributed to the in situ formed Ni II /Ni III redox active species.Such astrategy can deliver avariety of DHIQs bearing electron-withdrawing/ donating groups in good yields and excellent selectivities,a nd can be applied to gram-scale synthesis.Atwo-electrode Ni 2 P bifunctional electrolyzer can produce both H 2 and DHIQs with robust stability and high Faradaic efficiencies at am uch lower cell voltage than that of overall water splitting.Electrocatalytic water splitting represents ap romising way to produce clean hydrogen (H 2 ). [1] Thesluggish kinetics of the oxygen evolution reaction (OER), however, often limits the overall water splitting efficiency. [2] Although some welldesigned electrocatalysts have been developed to promote the kinetics of the OER, [3] alarge potential is still required to match hydrogen evolution reaction (HER), leading to low energy conversion efficiency. An alternative strategy that replacing the anodic OER with the electrooxidation of thermodynamically more favorable species is of increasing importance to boost HER. [4] Am yriad of value-added chemicals,r ather than O 2 ,a re produced at anode.N evertheless,i nm ost cases,t he fully electrooxidized products are obtained. [4a] Thus,u sing electrooxidative power to drive controllable transformations of chemicals into corresponding semi-oxidized products with high selectivity and industrial practicability is highly challenging but more significant.Dihydroisoquinolines (DHIQs) display aw ide range of bioactivities on anti-tumor,a nti-fungal, vasodilation and nonoamine oxidase inhibition, which demonstrate highly potential applications in pharmaceutical industry. [5] The dehydrogenation of tetrahydroisoquinolines (THIQs) is ap otential way to synthesize the DHIQs,b ut the typical thermal-and photocatalytic strategies usually lead to the complete dehydrogenation products,i soquinolines (IQs). [6] Thes emi-dehydrogenation products (DHIQs) are more difficult to obtain, especially via as ustainable route,s uch as electrochemical dehydrogenation. [7] Therefore,t he controllable electrooxidation from THIQs to DHIQs with high selectivity at low potential over al ow cost electrocatalysts, especially coupled with efficient HER, will be economically attractive,but remains highly challenging.Herein, we demonstrate an efficient strategy to promote H 2 production by replacing OER with selective semi-dehydrogenation of THIQs over aN i 2 Pa node (Figure 1). The in situ formed Ni II /Ni III r...

Alcohols electrooxidation coupled with H2 production at high current densities promoted by a cooperative catalyst

“…For reactions of this kind, applying large positive potential would unavoidably result in uncontrolled OER, therefore applying moderate potential is necessary to achieve high Faradaic efficiency (FE) toward target products 7 . Tremendous efforts have been devoted to developing electrocatalysts with improved catalytic activities towards various oxidation reactions 8 – 13 . Despite these efforts, the reported current density remains very low under moderate cell potential, for example, the electrooxidation of alcohols 8 , 9 , 5-hydroxymethyfurfural (HMF) 10 , 11 , primary amines 12 and tetrahydroisoquinolines 13 are mostly operated at current density lower than 200 mA cm –2 .…”

Two‐Dimensional NiIr@N‐Doped Carbon Nanocomposites Supported on Ni Foam for Electrocatalytic Overall Water Splitting

“…[14][15][16] As a3 dt ransition metal,n ickel (Ni)a nd its derivatives show considerable promise in electrocatalysis owing to their high abundance and unique physical and chemical properties.Avariety of Ni-based materialsh ave been demonstratedt ob ev ery promisingf or the electrocatalytic HER, OER, and even overall water splitting. [17][18][19][20][21][22][23][24] However,f or most of them, the catalytic performance and stability is still unsatisfactory compared with benchmark noble-metal-based catalysts. Moreover,t he survival environment of the water splitting reaction( e.g.,s trong acidic or alkalinem ediums, higho verpotentials) is difficult for Nibased materials, easily leading to corrosion or oxidation of the metal catalysts.…”

Accelerating Hydrogen Evolution by Anodic Electrosynthesis of Value‐Added Chemicals in Water over Non‐Precious Metal Electrocatalysts

“…In 2019, Zhang et al. observed the Ni II /Ni III redox pair via potential‐dependent Raman spectra (Figure 4a–c), which efficiently promoted the semi‐dehydrogenation reaction as a redox active species in situ formed on the Ni 2 P surface [28] . A more direct evidence for this redox active species came from the LSV curve without organic substrates.…”

“…Following this study, Ni 2 P electrocatalyst has been employed to couple many other organic oxidation reactions with HER, such as furfural or benzylamine oxidation and semi‐dehydrogenation conversion of tetrahydroisoquinolines [27–29] . In addition, Sun et al.…”