Low Onset Potential Research Articles

Enhanced alkaline ammonia oxidation reaction activity using PtW alloy catalysts with tungsten as built-in competitor reservoir

Direct ammonia anion exchange membrane fuel cells (DA-AEMFCs) have drawn great attention recently with the recognition that liquid ammonia (NH3), as a carbon-free hydrogen storage medium, is easy to store, transport, and distribute. However, its practical application is significantly limited by the anodic ammonia oxidation reaction (AOR), which not only is kinetically sluggish, but also suffers from competitive adsorption of oxidizing agent, OH–. Herein, we tackle the above challenges simultaneously by alloying the highly active platinum with electron-deficient tungsten. The W sites would preferentially adsorb *OH to serve as the reservoir and supply for the dehydrogenation of NH3. The Pt sites are thus liberated and free for the targeting adsorption of NH3. Moreover, density functional theory calculations suggest that, with the pre-adsorption of *OH, the d band center of PtW alloy experiences a positive shift toward the Fermi level, which would contribute to stronger adsorption of the reaction intermediates and thus benefit the whole AOR process. As expected, the synthesized alloy with the optimum ratio exhibits a low onset potential of 0.46 V versus reversible hydrogen electrode and a large peak current density of 11.70 mA cm−2. When subjected to practical application, the DA-AEMFCs assembled with such electrocatalyst deliver an excellent peak power density of 22.47 mW cm−2, indicating its potential feasibility in the next-generation energy devices.

Theoretical insights into heteronuclear dual metals on non-metal doped graphene for nitrogen reduction reaction

Electrochemical nitrogen reduction reaction (eNRR) is a promising strategy for sustainable ammonia production. To achieve high yield and energy efficiency, single-atom dispersion on nitrogen-doped graphene nanosheets has been extensively explored as an electrocatalyst for eNRR. However, challenges remain owing to the high overpotentials arising from unitary active sites and unabundant ligands. In this study, heteronuclear dual-metal catalysts with different non-metals doped in a graphene frame were computationally designed. After a two-step scanning based on density functional theory calculations, five candidates, namely FeMo-S, RuMo-B, RuMo-P, RuMo-S, and RuW-S, were identified as promising catalysts with calculated onset potentials of –0.18, –0.25, –0.27, –0.29, and –0.24 V, respectively. These catalysts can also effectively suppress the competitive hydrogen evolution reaction during NRR. Such excellent catalytic performance origins from two synergetic effects: (1) the cooperation of heteronuclear metals contribute to the electron transfer from active sites to the anti-bonding orbitals of N2 molecules adsorbed on catalysts to effectively activate N≡N bonds; (2) metal-ligands (non-metals) interactions moderate the binding strength of intermediates to slab, which is one of reasons for low NRR onset potential and high NH3 selectivity. The present study provides a theoretical understanding of the NRR mechanism of dual-metal catalysts, offering useful guidance for the rational design of catalysts with high selectivity and activity for NRR.

PGM-Based Ammonia Oxidation Catalysts for Anion-Exchange Membrane Direct Ammonia Fuel Cells

Low-temperature direct ammonia fuel cells (DAFCs) use carbon-neutral ammonia as a fuel, which has attracted increasing attention recently due to ammonia's low source-to-tank energy cost, easy transport and storage, and wide availability. However, current DAFC technologies are greatly limited by the kinetically sluggish ammonia oxidation reaction (AOR) at the anode. Herein, we report an AOR catalyst, in which ternary PtIrZn nanoparticles with an average size of 2.3 ± 0.2 nm were highly dispersed on a binary composite support comprising cerium oxide (CeO2) and zeolitic imidazolate framework-8 (ZIF-8)-derived carbon (PtIrZn/CeO2-ZIF-8) through a sonochemical-assisted synthesis method. The PtIrZn alloy, with the aid of abundant OHad provided by CeO2 and uniform particle dispersibility contributed by porous ZIF-8 carbon (surface area: ∼600 m2 g−1), has shown highly efficient catalytic activity for the AOR in alkaline media, superior to that of commercial PtIr/C. The rotating disk electrode (RDE) results indicate a lower onset potential (0.35 vs. 0.43 V), relative to the reversible hydrogen electrode at room temperature, and a decreased activation energy (∼36.7 vs. 50.8 kJ mol−1) relative to the PtIr/C catalyst. Notably, the PtIrZn/CeO2-ZIF-8 catalyst was assembled with a high-performance hydroxide anion-exchange membrane to fabricate an alkaline DAFC, reaching a peak power density of 91 mW cm−2. Unlike in aqueous electrolytes, supports play a critical role in improving uniform ionomer distribution and mass transport in the anode. PtIrZn nanoparticles on silicon dioxide (SiO2) integrated with carboxyl-functionalized carbon nanotubes (CNT–COOH) were further studied as the anode in a DAFC. A significantly enhanced peak power density of 314 mW cm−2 was achieved. Density functional theory calculations elucidated that Zn atoms in the PtIr alloy can reduce the theoretical limiting potential of *NH2 dehydrogenation to *NH by ∼0.1 V, which can be attributed to a Zn-modulated upshift of the Pt–Ir d-band that facilitates the N–H bond breakage.

(Invited) Dilute Anion Alloyed III-Nitride Nanowires for Photoelectrochemical Water Splitting

The record efficiencies in photovoltaic devices and hydrogen production via photoelectrochemical water splitting have been achieved in both cases by employing complex architectures of III-V alloys 1, which has been enabled by the outstanding charge carrier transport properties, band gap and band edge engineering flexibility, as well as highly mismatch growth that can be achieved in III-V alloys by controlling their chemical composition.It has been extensively demonstrated that Molecular Beam Epitaxy (MBE) and Metal-Organic Physical Vapor Deposition (MOPVD) techniques can produce III-V multinary alloys with compositions beyond miscibility gaps due to their “far from equilibrium” nature. And although great progress has been made towards improving the growth rate in these techniques, III-V device synthesis cost is still significantly higher (one order of magnitude) than Si solar cells manufacturing technologies 2. In this context, it is necessary to develop novel synthesis methods that yield high crystalline quality III-V alloys, higher throughput, and lower operational cost. For instance, Hydride/Halide Vapor Phase Epitaxy HVPE-grown GaAs top cell incorporated in a GaAs/Si tandem cell is an example of an optimized photovoltaic device with 31.4% efficiency, showcasing the uttermost potential of this growth method 2.More recently, Halide Vapor Phase Epitaxy growth of GaSbzP1-z polycrystalline free-standing films with up to 6.7% antimony incorporation and growth rates around 500 µm/h has been reported3. Linear sweep voltammetry measurements in 1M H2SO4 using GaSbzP1-z photoanodes showed lower onset potentials and higher fill factors compared to single crystal GaP. These results have been attributed to the visible light absorbing capabilities (direct band gaps between 2.2 and 2.5 eV), and lower charge transfer resistance at the semiconductor/electrolyte interface.On the other hand, a novel method for gallium nitridation involving plasma-activated nitrogen species dissolution into molten gallium has enabled the growth of single crystal GaN4. Furthermore, dilute anion Ga-Nitride alloys have been synthesized with the same technique but including other V-group species ions, i.e., Sb+ and Bi+, that can substitute nitrogen forming ternary GaSbxN1-x and GaBiyN1-y.In this presentation, we show the progress with dilute anion alloyed III-Nitride nanowires, GaSbxN1-x and GaBiyN1-y, synthesized by dissolving gallium, antimony or bismuth and plasma-activated nitrogen species into copper or gold droplets. Antimony and bismuth incorporation levels determined through x-ray diffraction c-plane peak shift, x and y, reached levels as high as 5.6 and 8.8 at%, respectively, resulting in direct band gap energies around 2.0 eV, determined through diffuse reflectance and photocurrent spectroscopy measurements. The visible light absorbing nanowire films exhibited photocurrent onset potentials around 0.0 V vs RHE when tested in 1 M sulfuric acid solution and 3-electrode setup with Ag/AgCl reference and Pt counter electrodes. 2-electrode chronoamperometry measurements with p-Si and n-type dilute alloys showed stable photocurrent densities up to 8.5 mA*cm-2 in 30 h. These results show the promising potential of dilute anion alloyed III-Nitrides as stable photoanodes for water splitting applications, and demonstrate the advantage of this novel synthesis technique over MOCVD that in previous studies has enabled the obtention of 0-D or 1-D GaSbxN1-x structures with up to 7% anion incorporation, while compromising crystalline quality.5

Ozone direct electro-generation/activation peroxymonosulfate (PMS) for the degradation of bisphenol A using Ti/NATO anode

In this study, Ni-doped Ti/SnO2-Sb anode (Ti/NATO) was prepared and used for electrocatalytic ozone production and in-situ activated peroxymonosulfate (E-Ti/NATO-PMS) to degrade bisphenol A (BPA). SEM, XRD and XPS results indicated that Ni doping could influence the transformations of Sb5+ and Sb3+ ions, which decreased the agglomeration of crystallites and increased the Oads and oxygen vacancy (Ov) concentrations. Ti/NATO1.0 anodes significantly improved the ozone production via outcompeting of the adsorbed O2ads over water, and inhibiting the desorption of O2ads, to obtain the highest O3 concentration with low onset potential and high oxygen evolution potential. E-Ti/NATO1.0-PMS system obtained over 92% BPA degradation within 60 min at 10 mA cm−2 and pH ranging from 4 to 10. Radical scavenging experiments revealed that O3in situ generated could directly electro-activate PMS into •O2− and 1O2. The E-Ti/NATO1.0-PMS process could detoxify the BPA through chain scission, rearrangement and ring opening processes, and exhibited great potentials for application.

Citrate modulation of CoAl(OH)x Catalyst/Sb–TiO2 nanorods interface boosting photocarrier separation and injection for enhanced water oxidation

The design of an oxygen evolution catalyst (OEC) coupled photoanode ensuring effective charge separation, transfer, and injection is always desirable for enhanced water oxidation kinetics. Here, we have designed Sb-doped TiO2 nanorods (NRs) photoanode coupled with the ultrathin amorphous CoAl(OH)x OEC via citrate anion bridging. The CoAl(OH)x performs as a hole scavenger OEC, a hole storage layer, surface defect passivation layer, and also generates a band banding leading to the built-in potential at the semiconductor/catalyst interface favoring rapid hole separation. The citrate linking improves the CoAl(OH)x/Sb–TiO2 interfacial bonding and reduces the interfacial impedance to boost the photocarrier separation. Citrate bridging also serves as an efficient hole extraction layer and transportation pathway and promotes oxygen vacancy formation, which favors adsorbing OH− during the OER. As a result, the CoAl(OH)x/cit/Sb–TiO2 NRs photoanode exhibits a superior photocurrent density of 1.73 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (VRHE), close to the theoretical maxima of titanium dioxide, with a very low onset potential of 0.12 VRHE and an extremely high hole injection efficiency of 93.1%. This work demonstrates an effective design strategy to boost the performance of OER catalyst coupled photo harvesting semiconductor photoanodes to achieve efficient solar water splitting.

Design and performance analysis of a PV-assisted alkaline electrolysis for hydrogen production: An experimental and theoretical study

The PV assisted alkaline electrolysis cell was established for hydrogen generation. Lab-made AgNiCu modified nickel foam cathodes were used in this system. The characterization was achieved using field emission scanning electron microscopy, energy-dispersive X-ray and X-Ray diffraction analysis. The electrochemical performance was investigated via linear sweep voltammetry, cyclic voltammetry, Tafel polarization measurements and electrochemical impedance spectroscopy. The electrolysis potential and time depended efficiency was monitored. The structural theoretical analysis of the electrode surface and hydrogen evolution characteristics were also determined applying Density Functional Theory and Ab-initio Molecular Dynamics simulations which identified the role of Ag decoration and Cu incorporation on the surface against water and proton adsorptions. The modified cathode (AgNiCuF) improved the hydrogen production performance owing to lower hydrogen onset potential (−1.1 V) and charge transfer resistance (0.362 ohm at −1.5 V).

Highly efficient electrosynthesis of H2O2 in acidic electrolyte on metal-free heteroatoms co-doped carbon nanosheets and simultaneously promoting Fenton process

Recently electrochemical synthesis of H2O2 through oxygen reduction reaction (ORR) via 2e− pathway is considered as a green and on-site route. However, it still remains a big challenge for fabricating novel metal-free catalysts under acidic solutions, since it suffers from high overpotential due to the intrinsically week *OOH adsorption. Herein, a co-doped carbon nanosheet (O/NC) catalyst toward regulating O and N content was synthesized for improving the selectivity and activity of H2O2 electrosynthesis process. The O/NC exhibits outstanding 2e− ORR performance with low onset potential of 0.4 V (vs. RHE) and a selectivity of 92.4% in 0.1 mol/L HClO4 solutions. The in situ electrochemical impedance spectroscopy (EIS) tests reveals that the N incorporation contributes to the fast ORR kinetics. The density functional theory (DFT) calculations demonstrate that the binding strength of *OOH was optimized by the co-doping of oxygen and nitrogen at certain content, and the O/NCCOOH site exhibits a lower theoretical overpotential for H2O2 formation than OCCOOH site. Furthermore, the promoted kinetics for typical organic dye degradation in simultaneous electron-Fenton process on O/NC catalyst was demonstrated particularly for broadening its environmental application.

Quenching-assisted surface functionalization of metal oxide for highly enhanced electrocatalytic urea oxidation

Urea oxidation reaction (UOR) is considered as a good substitute for oxygen evolution reaction (OER) because of its low theoretical onset potential. Surface modification is an effective strategy to tune the catalytic activity of the catalysts towards UOR. Here, we developed a facile and universal quenching strategy to prepare sulfate-modified NiO nanosheets (NiO@NF-20S). Compared with the pristine NiO nanosheets, the electrocatalytic performance of the NiO@NF-20S is greatly improved, showing a small potential of 1.40 V vs. RHE to deliver a current density of 200 mA cm−2 as well as robust electrochemical stability. The outstanding electrocatalytic performance of the NiO@NF-20S is mainly ascribed to the improved surface wettability and the promoted Ni2+/Ni3+ redox reaction. The quenching strategy can be expanded to not only various kinds of functional groups from nitric acid and phosphoric acid but also other metal oxides such as NiCoOx and NiCrOx. This work provides a new avenue to the design of surface-functionalized metal oxide catalysts for electrocatalysis.

Controlled Fabrication of Hierarchically Structured MnO2@NiCo-LDH Nanoarrays for Efficient Electrocatalytic Urea Oxidization.

Urea, a prevalent component found in wastewater, shows great promise as a substrate for energy-efficient hydrogen production by electrolysis. However, the slow kinetics of the anodic urea oxidation reaction (UOR) significantly hamper the overall reaction rate. This study presents the design and controlled fabrication of hierarchically structured nanomaterials as potential catalysts for UOR. The prepared MnO2@NiCo-LDH hybrid catalyst demonstrates remarkable improvements in reaction kinetics, benefiting from synergistic enhancements in charge transfer and efficient mass transport facilitated by its unique hierarchical architecture. Notably, the catalyst exhibits an exceptionally low onset potential of 1.228 V and requires only 1.326 V to achieve an impressive current density of 100 mA cm-2, representing a state-of-the-art performance in UORs. These findings highlight the tremendous potential of this innovative material designing strategy to drive advancements in electrocatalytic processes.

Enhanced Spatial Charge Separation in a Niobium and Tantalum Nitride Core-Shell Photoanode: In Situ Interface Bonding for Efficient Solar Water Splitting.

Tantalum nitride (Ta3N5) has emerged as a promising photoanode material for photoelectrochemical (PEC) water splitting. However, the inefficient electron-hole separation remains a bottleneck that impedes its solar-to-hydrogen conversion efficiency. Herein, we demonstrate that a core-shell nanoarray photoanode of NbNx-nanorod@Ta3N5 ultrathin layer enhances light harvesting and forms a spatial charge transfer channel, which leads to the efficient generation and extraction of charge carriers. Consequently, an impressive photocurrent density of 7 mA•cm-2 at 1.23 VRHE is obtained with an ultrathin Ta3N5 shell thickness of less than 30 nm, accompanied by excellent stability and a low onset potential (0.46 VRHE). Mechanistic studies reveal the enhanced performance is attributed to the high-conductivity NbNx core, high-crystalline Ta3N5 mono-grain shell, and the intimate Ta-N-Nb interface bonds, which accelerate the charge separation capability of the core-shell photoanode. This study demonstrates the key roles of nanostructure design in improving the efficiency of PEC devices.

Enhanced Spatial Charge Separation in a Niobium and Tantalum Nitride Core‐Shell Photoanode: In Situ Interface Bonding for Efficient Solar Water Splitting

AbstractTantalum nitride (Ta3N5) has emerged as a promising photoanode material for photoelectrochemical (PEC) water splitting. However, the inefficient electron‐hole separation remains a bottleneck that impedes its solar‐to‐hydrogen conversion efficiency. Herein, we demonstrate that a core–shell nanoarray photoanode of NbNx‐nanorod@Ta3N5 ultrathin layer enhances light harvesting and forms a spatial charge‐transfer channel, which leads to the efficient generation and extraction of charge carriers. Consequently, an impressive photocurrent density of 7 mA cm−2 at 1.23 VRHE is obtained with an ultrathin Ta3N5 shell thickness of less than 30 nm, accompanied by excellent stability and a low onset potential (0.46 VRHE). Mechanistic studies reveal the enhanced performance is attributed to the high‐conductivity NbNx core, high‐crystalline Ta3N5 mono‐grain shell, and the intimate Ta−N−Nb interface bonds, which accelerate the charge‐separation capability of the core–shell photoanode. This study demonstrates the key roles of nanostructure design in improving the efficiency of PEC devices.

Fast joule heating synthesis of NiCoFeCrMo high-entropy alloy embedded in graphene for water oxidation

High-entropy alloys (HEAs) are considered as considerable candidate for electrocatalytic water splitting. The main holdback locates in fabricating well-defined HEAs with moderate electronic structure and uncovering the structural evolution during the reaction process. Herein, we successfully synthesized NiCoFeCrMo HEA-nps by an ultrafast joule heating method for highly efficient oxygen evolution reaction (OER). The optimal graphene incorporated NiCoFeCrMo HEA nanoparticles (HEA-nps) exhibits finely distributed nanoparticles with average size of 17.49 nm and uniformly distribution of all the five elements, which displays the outstanding OER performance with a low onset potential and only requires the 260 mV (vs RHE) to achieve the current density of 10 mA cm−2. X-ray absorption fine structure (XAFS) demonstrates that the high valence Cr and Mo can directly regulate the local structure of HEA-nps, which significantly promoted the intrinsic activity of high active species. This work not only provides a design strategy related to the high valence elements injection for HEAs, but also uncovers the structural evolution of HEAs during OER process.

Unveiling the intrinsic properties of single NiZnFeOx entity for promoting electrocatalytic oxygen evolution

Although considerable research efforts have been devoted to the design and development of non-noble electrocatalysts for oxygen evolution reaction (OER), substantial enhancement of OER performance with commercial-scale water electrolysis remains a big challenge. This could result from the difficulties in detecting the intrinsic properties and overlooking the assembly process for electrochemical OER process. Here, we employ a microjet collision method to investigate the intrinsic OER activities of individual NiZnFeOx entities with and without a moderate magnetic field. Our results demonstrate that single NiZnFeOx nanoparticles (NPs) show the excellent OER performance with a lowest onset potential (∼1.35 V vs. RHE) and a greatest magnetic enhancement (∼118%) among bulk materials, single agglomerations and NPs. Furthermore, we explore the utility of theoretical investigation by density functional theory (DFT) calculations for studying OER process on NiZnFeOx surfaces without and with spin alignment, indicating monodispersed NiZnFeOx NPs with totally spin alignment facilitates the OER process under the external magnetic field. It is found that the well-dispersion of NiZnFeOx NPs would increase the electrical conductivity and the surface spin state, resulting in promoting their OER activities. This work provides a test for uncovering the essential roles of NPs assembly to a significant promotion of their magnet-assisted OER.

Nickel molybdate nanorods synthesized on carbon cloth as an electrocatalyst for methanol oxidation and hydrogen evolution reactions

In this report, the nickel molybdate (NiMoO4) nanorods were grown on carbon cloth (CC) with an average length of 3 µm and a diameter of 130 nm. The NiMoO4/CC demonstrated a lower onset potential of 0.553 V vs. Hg/HgO at 10 mA/cm2 for methanol oxidation reaction (MOR). In addition, the electrocatalyst showed notable cyclic stability, where the onset potential attained 0.585 and 0.616 V vs. Hg/HgO at 10 mA/cm2 during the 250th and 1000th cycles, respectively. In the hydrogen evolution reaction (HER), the NiMoO4/CC exhibited good performance with an overpotential of −0.517 V vs. RHE at 10 mA/cm2, the Tafel slope of 144 mV/dec, and a turnover frequency of 1.298H2/active site. The higher active sites (2.594 × 1017 cm2) and high electrochemical surface area (94.63 cm2) of NiMoO4/CC electrocatalyst exhibited stable and efficient MOR and HER performances.

Efficient 1D ZnO/Cu2S heterostructure photocatalyst on topological Ag molded PVDF polymer fiber matrix for photoelectrochemical hydrogen evolution applications

A heterostructure semiconductor photo-electrocatalyst ZnO/Cu2S-loaded PVDF polymer matrix is used for solar water splitting. Herein, Ag nanoparticle-casted electrospun PVDF polymer matrix fibers have been used as a platform to fabricate the 1D ZnO nanorods as a photo-electrocatalyst. The Cu2S nanoparticles passivated on the 1D ZnO nanoarray show a two-fold enhancement of the photoelectrochemical hydrogen evolution. The conducting Ag nanoparticles sensitized PVDF, enhancing the conductance, and synergistically contributed to the water splitting under white light illumination. The PVDF/Ag/ZnO/Cu2S photoanode demonstrated photoelectrochemical water splitting. Ag nanoparticles (Ag NP), 1D nanostructures, and Cu2S narrowband gap semiconductors integrated into the photoanode accelerate the oxidation of the water through more visible absorption and high charge carrier transport. The PVDF/Ag/ZnO/Cu2S photoanode generates a stable saturated photocurrent density of 0.62 mA/cm2 in the −0.2 to 0.4 V vs. Ag/AgCl potential window. The chemically inert PVDF fibers with an Ag metal surface show a low onset potential and a charge transfer resistance of 844 Ohm/cm2 with a 0.42% photon to electron conversion efficiency for solar water splitting. Solar water oxidation has been demonstrated under unbiased conditions.

Awakening (220) as One More Active Facet of PtMo Alloy via Single‐Atom Doping to Boost Ammonia Electrooxidation in Direct Ammonia Fuel Cell

AbstractAs the core of low‐temperature direct ammonia fuel cell (DAFC) technology, electrocatalytic ammonia oxidation reaction (AOR) has proven to be most active on platinum‐based catalysts. However, the AOR is extremely surface sensitive that only the Pt (200) facet exhibits high reaction activity, whereas other facets usually do not make contributions. Herein, the inert (220) surface of PtMo nano‐alloy is successfully awakened as one more active facet in addition to (200) via directional single‐atom Ni‐doping. The introduction of Ni triggers a targeted electron accumulation around Pt sites at the (220) facet that significantly reduces the AOR energy barrier while maintaining the activity of the (200) surface. With a greatly enlarged active surface, the Ni‐decorated PtMo catalyst exhibits a significantly facilitated AOR kinetics with a low onset potential of 0.49 V versus reversible hydrogen electrode and a superior peak current density of 94.96 A g−1 at 5 mV s−1. Notably, the DAFC equipped with such an electrocatalyst reaches a remarkable peak power density of 16.70 mW cm−2 at low temperatures. It is believed that this strategy sheds light on exploiting the intrinsic activity of Pt‐based electrocatalysts, and drives the low‐temperature DAFC technology to a more practical level.

Unveiling the high activity origin of NiFe catalysts decorated Ta3N5 photoanodes for oxygen evolution reaction

Bimetallic NiFe catalysts could effectively promote the photoelectrochemical (PEC) water splitting activities of Ta3N5 photoanodes, while exploring the intrinsic activity origin is crucial for constructing highly efficient solar-energy conversion systems. Herein, we demonstrate a simple impregnation strategy for rational deposition of NiFe catalysts nanolayers on Ta3N5 nanotube photoanodes, which achieved a superior photocurrent density of 11.2 mA cm−2 at 1.23 V versus the reversible hydrogen electrode (RHE) accompanied by a low onset potential (0.3 VRHE). More importantly, systematic studies reveal that the preferred deposition of Fe catalysts nanolayers on Ta3N5 photoanode surfaces could effectively promote the charge separation and hole transfer, while the subsequent formation of Ni catalysts nanolayers could provide the catalytic active-sites for water oxidation. Accordingly, their synergistic effects significantly improve the interfacial hole transfer and surface oxygen evolution kinetics, leading to an outstanding PEC water splitting activity. This work not only clarifies the intrinsic high-activity origins of NiFe/Ta3N5 photoanodes, but also provides new insights into the rational construction of highly efficient OER catalysts for PEC water splitting.

The effect of branched versus linear side chain on thieno[3,4-c]pyrrole-4,6-dione-based donor-acceptor-donor type monomers and their p- and n-dopable polymers

The conjugated backbone has been the focus of the most research, while the structure of the side chains has received less attention. Here, we focus on making new donor–acceptor–donor (D–A–D) type conjugated monomers by bearing a thieno[3,4-c]pyrrole-4,6-dione (TPD) with octyl chain at the imide nitrogen as the acceptor unit and 3,4-ethylenedioxythiophene (EDOT), and 3,3-didecyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine (ProDOT) as the donor units and their corresponding polymers. The optical and electrochemical properties of octyl substituted monomers and their corresponding polymers were compared with their ethylhexyl counterparts. Changing the alkyl side chain on the TPD unit from linear to branched has no effect on onset potential, optical band gap (Eg), perceived color, electrochromic contrast, or switching time. Nonetheless, donor strength has significant impact on the properties of monomers and their corresponding polymers. EDOT-bearing monomers and polymers have lower onset and oxidation potentials, Eg values than their ProDOT counterparts due to more electron donating ability of ethylenedioxy bridge in comparison to the propylenedioxy bridge. Octyl substituted monomers, P-Octyl and E-Octyl, demonstrated high sensitivity towards the Fe3+ ion, making them viable candidates for use in ion sensing, and their corresponding polymers, PE-Octyl and PP-Octyl, are both p- and n-dopable, which is a desirable property for conjugated polymers. Furthermore, PP-Octyl was found to be soluble in common solvents, and PP-Octyl in toluene can be oxidized with antimony pentachloride (SbCl5).

Enabling high-efficiency ethanol oxidation on NiFe-LDH via deprotonation promotion and absorption inhibition

Nucleophile oxidation reaction (NOR), represented by ethanol oxidation reaction (EOR), is a promising pathway to replace oxygen evolution reaction (OER). EOR can effectively reduce the driving voltage of hydrogen production in direct water splitting. In this work, large current and high efficiency of EOR on a Ni, Fe layered double hydroxide (NiFe-LDH) catalyst were simultaneously achieved by a facile fluorination strategy. F in NiFe-LDH can reduce the activation energy of the dehydrogenation reaction, thus promoting the deprotonation process of NiFe-LDH to achieve a lower EOR onset potential. It also weakens the absorption of OH− and nucleophile electrooxidation products on the surface of NiFe-LDH at a higher potential, achieving a high current density and EOR selectivity, according to density functional theory calculations. Based on our experiment results, the optimized fluorinated NiFe-LDH catalyst achieves a low potential of 1.386 V to deliver a 10 mA cm−2 EOR. Moreover, the Faraday efficiency is greater than 95%, with a current density ranging from 10 to 250 mA cm−2. This work provides a promising pathway for an efficient and cost-effective NOR catalyst design for economic hydrogen production.