Understanding the pH Dependence of Underpotential Deposited Hydrogen on Platinum

Understanding the pH dependent shift of the oxidation peak of the underpotential deposited hydrogen (H_upd) in cyclic voltammograms on the Pt surface is of significance in terms of both the fundamentals of electrochemistry and the rational design of catalysts for the hydrogen oxidation/evolution reactions (HOR/HER). In this work, we provide compelling evidence that the pH dependent shift in the H_upd peak on Pt surfaces is driven by the structure of interfacial water rather than the specific adsorption of cations on the electrode surface. Combined cyclic voltammetric and surface enhanced spectroscopic investigations using an organic cation and crown‐ether chelated alkali metal cations show that specific adsorption of metal and organic cations on the Pt surface at the conditions relevant to the HOR/HER is unlikely. The vibrational band corresponding to strongly bound water is monitored when the electrode potential is varied in the H_upd range in both acid and base.     

pH effect on electrocatalytic reduction of CO2 over Pd and Pt nanoparticles

Adsorbed hydrogen participates in electrocatalytic reduction of CO₂ and competitive hydrogen evolution reaction (HER) simultaneously, and its reaction pathway greatly affects the activity and selectivity of CO₂ reduction. In this work, we investigate pH effect on electrocatalytic reduction of CO₂ over Pd and Pt nanoparticles (NPs) with a similar size in a pH range from 1.5 to 4.2. Pt NPs completely contribute to HER in the pH range. Over Pd NPs, Faradaic efficiency for CO production at − 1.19 V (vs. reversible hydrogen electrode) varies from 3.2% at pH of 1.5 to 93.2% at pH of 4.2, and current density for CO production reaches maximum at pH of 2.2. The significant enhancement of Faradaic efficiency and current density for CO production over Pd NPs at high pH values is attributed to decreased kinetics of hydrogen evolution reaction by increasing hydrogen binding energy and lowered adsorption affinity of CO-like intermediate compared to Pt.     

Boron-Induced Electronic-Structure Reformation of CoP Nanoparticles Drives Enhanced pH-Universal Hydrogen Evolution

Even though transition-metal phosphides (TMPs) have been developed as promising alternatives to Pt catalyst for the hydrogen evolution reaction (HER), further improvement of their performance requires fine regulation of the TMP sites related to their specific electronic structure. Herein, for the first time, boron (B)-modulated electrocatalytic characteristics in CoP anchored on the carbon nanotubes (B-CoP/CNT) with impressive HER activities over a wide pH range are reported. The HER performance surpasses commercial Pt/C in both neutral and alkaline media at large current density (>100 mA cm⁻²). A combined experimental and theoretical study identified that the B dopant could reform the local electronic configuration and atomic arrangement of bonded Co and adjacent P atoms, enhance the electrons’ delocalization capacity of Co atoms for high electrical conductivity, and optimize the free energy of H adsorption and H₂ desorption on the active sites for better HER kinetics.     

Boron‐Induced Electronic‐Structure Reformation of CoP Nanoparticles Drives Enhanced pH‐Universal Hydrogen Evolution

Even though transition‐metal phosphides (TMPs) have been developed as promising alternatives to Pt catalyst for the hydrogen evolution reaction (HER), further improvement of their performance requires fine regulation of the TMP sites related to their specific electronic structure. Herein, for the first time, boron (B)‐modulated electrocatalytic characteristics in CoP anchored on the carbon nanotubes (B‐CoP/CNT) with impressive HER activities over a wide pH range are reported. The HER performance surpasses commercial Pt/C in both neutral and alkaline media at large current density (>100 mA cm^?2). A combined experimental and theoretical study identified that the B dopant could reform the local electronic configuration and atomic arrangement of bonded Co and adjacent P atoms, enhance the electrons’ delocalization capacity of Co atoms for high electrical conductivity, and optimize the free energy of H adsorption and H₂ desorption on the active sites for better HER kinetics.     

Hydrogen evolution reaction on Pt and Ru in alkali with volmer-step promotors and electronic structure modulators

Alkaline water electrolysis despite having a variety of choices for anodic oxygen evolution reaction (OER) catalysts out of non-precious metals suffers significantly due to the poor kinetics of cathodic hydrogen evolution reaction (HER) even with the state-of-the-art Pt and equally active Ru. The Volmer-step (water dissociation (WD) coupled proton adsorption) of alkaline HER is mostly the rate-determining step (RDS) and costs most of the work required. In this review, recent developments in improving the HER kinetics of Pt and Ru with Volmer-step promotors and electronic structure modulators have been comprehensively analyzed and critically presented with the challenges and prospects.     

Chemical Adsorption onto an ITO Substrate of Single‐Wall Carbon Nanotube Functionalized by Carboxylic Groups as an Efficient Support for Electrocatalyst

A single‐wall carbon nanotube functionalized by carboxylic groups (SWNT‐CA) was found to be adsorbed on an indium tin oxide (ITO) electrode by chemical interaction between carboxylic groups and the ITO surface. The adsorption experiments indicated that the narrow pH conditions (around pH 3.0) exist for its adsorption which is restricted by preparation of stable fluid dispersion (favorable at higher pH) and by the chemical interaction (favorable at lower pH). Atomic force microscopic (AFM) measurements suggest that fragmented SWNT‐CA are adsorbed, primarily lying on the surface. Electrochemical impedance analysis indicated that an electrochemical double layer capacitance of the SWNT‐CA/ITO electrode is considerably higher than that for the ITO electrode, suggesting that the interfacial area between the electrode surface and the electrolyte solution is enlarged by the SWNT‐CA layer. Pt particles were deposited as a catalyst on the bare ITO and SWNT‐CA‐coated ITO (SWNT‐CA/ITO) electrodes to give respective Pt‐modified electrodes (denoted as a Pt/ITO electrode and a Pt/SWNT‐CA/ITO electrode, respectively). The cathodic current for the Pt/SWNT‐CA/ITO electrode was 1.7 times higher than that for the Pt/ITO electrode at 0.0 V, showing that the Pt/SWNT‐CA/ITO electrode works more efficiently for O₂ reduction at 0.0 V due to the SWNT‐CA layer. The enhancement by the SWNT‐CA layer is also effective for electrocatalytic proton reduction. It could be ascribable to the enlarged interfacial area between the electrode surface and the electrolyte solution.     

Influence of the proton transport on the ORR kinetics and on the H2O2 escape in three-dimensionally ordered electrodes

In this study, we use rotating ring disc electrode measurements to investigate the influence of the proton transport on the kinetics of the oxygen reduction reaction (ORR) in a 3D nanostructured catalytic layer based on Pt nanoparticles supported on vertically aligned carbon nanofibers. The results confirm that protons are involved in the rate determining step of the ORR in acidic media. For pH ≥ 3, the ORR occurs in two successive reduction waves. The first current plateau is limited by the proton diffusion and is followed by the second reduction wave attributed to the mechanism involving water dissociation. The shape of the H₂O₂ escape current curve is strongly affected by the pH of the solution and shows a pronounced maximum when the pH value is increased. These experimental features are discussed with the help of a kinetic model.     

Effect of ZrS2 load single/dual-atom catalysts on the hydrogen evolution reaction: A first-principles study

The hydrogen evolution effect of ZrS₂ carrier loaded with transition metal single-atom (SA) was explored by first-principles method. ZrS₂ was constructed with transition metal single-atom and dual-atom. The structure–activity relationship of supported single-atom catalysts was described by electronic properties and hydrogen evolution kinetics. The results show that the ZrS₂ carrier-loaded atomic-level catalysts are more likely to occur in acidic environments, where the Mo SA load has a higher hydrogen precipitation capacity than the Pt SA. In the case of dual-atom adsorption, most of the hydrogen reduction processes are higher than that of single atom loading, which indicates that the outer orbital hybridization is more likely to lead to the interfacial charge recombination of the catalyst. Thereinto, Ni/Pt @ZrS₂ has the lowest Gibbs free energy (0.08 eV), and the synergistic effect of transition metals induces the deviation of the center of the d-band from the Fermi level and improves the dissociation ability of H ions. The design provides a new catalytic model for the HER and provides some ideas for understanding the two-site catalysis.     

Enhanced Hydrogen Evolution in Neutral Water Catalyzed by a Cobalt Complex with a Softer Polypyridyl Ligand

To explore the structure–function relationships of cobalt complexes in the catalytic hydrogen evolution reaction (HER), we studied the substitution of a tertiary amine with a softer pyridine group and the inclusion of a conjugated bpy unit in a Co complex with a new pentadentate ligand, 6‐[6‐(1,1‐di‐pyridin‐2‐yl‐ethyl)‐pyridin‐2‐ylmethyl]‐[2,2′]bipyridinyl (Py3Me‐Bpy). These modifications resulted in significantly improved stability and activity in both electro‐ and photocatalytic HER in neutral water. [Co(Py3Me‐Bpy)(OH₂)](PF₆)₂ catalyzes the electrolytic HER at ?1.3 V (vs. SHE) for 20 hours with a turnover number (TON) of 266 300, and photolytic HER for two days with a TON of 15 000 in pH 7 aqueous solutions. The softer ligand scaffold possibly provides increased stability towards the intermediate Co^I species. DFT calculations demonstrate that HER occurs through a general electron transfer/proton transfer/electron transfer/proton transfer pathway, with H₂ released from the protonation of Co^II?H species.     

Methodical aspects of studying the electroreduction of nitrate on modified single crystal Pt(hkl) + Cu electrodes

Technique of modification of basal faces Pt(hkl) by adatoms and epitaxial copper deposits is developed. Analysis of potentiostatic current transients of copper deposition/dissolution and atomic force microscopy showed that the activity of Pt(hkl) faces regarding the processes of copper nucleation and epitaxial growth increases in the sequence of Pt(111) < Pt(110) < Pt(100). The reaction of nitrate anion reduction is sensitive towards the surface structure, not only in the case of platinum, but also in the case of copper deposits (including a monolayer of adatoms). The highest process rate is observed for the Pt(100) electrode modified by a monolayer of adatoms or islands of bulk copper; nitrate reduction at the lowest rate occurs at Pt(111) + Cu electrodes. Structure-sensitive competitive adsorption of background electrolyte and nitrate anions is the factor that largely determines the kinetics of nitrate reduction on different faces of platinum single crystal and copper deposits.     

Interfacial Engineering of CdO–CdSe 3D Microarchitectures with in situ Photopolymerized PEDOT for an Enhanced Photovoltaic Performance

In the present work, porous 3D CdO‐microstructured electrode obtained by pyrolysis of 3D CdCO₃ microstructures is self‐sensitized with CdSe using an ion exchange reaction. After sensitization, an interfacial treatment of the CdO–CdSe interface is performed by depositing a thin film of PEDOT using a photoinduce polymerization route. The microstructured electrode before and after interfacial treatment is characterized using field‐emission scanning microscope, energy dispersive X‐ray analyzer, contact angle measurement, UV–Visible absorption spectrophotometer and X‐ray photoelectron spectrometer. After constructing a liquid junction solar cell with a Pt counter electrode, the photovoltaic performance and interfacial charge transfer kinetics across the CdO–CdSe interface before and after PEDOT treatment are investigated. The results exhibit an improved interfacial charge‐transfer resistance after the PEDOT treatment, which leads to enhance the short‐circuit current by 15.81% and the power conversion efficiency by 19.82%.     

Engineering the Coordination Environment of Single‐Atom Platinum Anchored on Graphdiyne for Optimizing Electrocatalytic Hydrogen Evolution

Two Pt single‐atom catalysts (SACs) of Pt‐GDY1 and Pt‐GDY2 were prepared on graphdiyne (GDY)supports. The isolated Pt atoms are dispersed on GDY through the coordination interactions between Pt atoms and alkynyl C atoms in GDY, with the formation of five‐coordinated C₁‐Pt‐Cl₄ species in Pt‐GDY1 and four‐coordinated C₂‐Pt‐Cl₂ species in Pt‐GDY2. Pt‐GDY2 shows exceptionally high catalytic activity for the hydrogen evolution reaction (HER), with a mass activity up to 3.3 and 26.9 times more active than Pt‐GDY1 and the state‐of‐the‐art commercial Pt/C catalysts, respectively. Pt‐GDY2 possesses higher total unoccupied density of states of Pt 5d orbital and close to zero value of Gibbs free energy of the hydrogen adsorption (|Δ |) at the Pt active sites, which are responsible for its excellent catalytic performance. This work can help better understand the structure–catalytic activity relationship in Pt SACs.     

铂配合物cis-[Pt(NH_3)_2(4-mepy)Cl]NO_3与甲基-谷胱甘肽作用的NMR研究

使用质子核磁共振方法测定了新的抗癌活性配合物cis－[Pt（NH3）2（4－mepy）Cl]＋与甲基-谷胱甘肽（GS－Me）的反应及其动力学．结果表明Pt与GS－Me间形成1：1加合物．为了解结合部位，对Pt－GS－Me配合物进行pH滴定，由GS－Me的质子核磁共振谱对pH的依赖关系判断Gs－Me只通过S原子与Pt配位，而氨基和羧基不参与配位反应．由配体吡啶环质子核磁共振随时间的变化，提出了两步反应机制：首先GS－Me通过S原子与Pt配位，然后由于S配位的高度反位效应使反应的NH3活动化．通过1HNMR方法测定了第一步反应的速率常数k＝0．017L·mol－1·s－1（pH3．1）和k＝0．013L·mol－1·s－1（pH7．2）．     

Ir Nanoparticles Anchored on Metal-Organic Frameworks for Efficient Overall Water Splitting under pH-Universal Conditions

The construction of high-activity and low-cost electrocatalysts is critical for efficient hydrogen production by water electrolysis. Herein, we developed an advanced electrocatalyst by anchoring well-dispersed Ir nanoparticles on nickel metal-organic framework (MOF) Ni-NDC (NDC: 2,6-naphthalenedicarboxylic) nanosheets. Benefiting from the strong synergy between Ir and MOF through interfacial Ni−O−Ir bonds, the synthesized Ir@Ni-NDC showed exceptional electrocatalytic performance for hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and overall water splitting in a wide pH range, superior to commercial benchmarks and most reported electrocatalysts. Theoretical calculations revealed that the charge redistribution of Ni−O−Ir bridge induced the optimization of H₂O, OH* and H* adsorption, thus leading to the accelerated electrochemical kinetics for HER and OER. This work provides a new clue to exploit bifunctional electrocatalysts for pH-universal overall water splitting.     

ZIF-Induced d-Band Modification in a Bimetallic Nanocatalyst: Achieving Over 44 % Efficiency in the Ambient Nitrogen Reduction Reaction

The electrochemical nitrogen reduction reaction (NRR) offers a sustainable solution towards ammonia production but suffers poor reaction performance owing to preferential catalyst–H formation and the consequential hydrogen evolution reaction (HER). Now, the Pt/Au electrocatalyst d-band structure is electronically modified using zeolitic imidazole framework (ZIF) to achieve a Faradaic efficiency (FE) of >44 % with high ammonia yield rate of >161 μg mg_cat⁻¹ h⁻¹ under ambient conditions. The strategy lowers electrocatalyst d-band position to weaken H adsorption and concurrently creates electron-deficient sites to kinetically drive NRR by promoting catalyst–N₂ interaction. The ZIF coating on the electrocatalyst doubles as a hydrophobic layer to suppress HER, further improving FE by >44-fold compared to without ZIF (ca. 1 %). The Pt/Au-N_ZIF interaction is key to enable strong N₂ adsorption over H atom.     

Br?nsted酸性离子液体活化电极催化制氢性能研究

分别采用玻碳( GC)、铂( Pt)和金( Au)电极研究了在Br?nsted酸性离子液体[ HMIm] HSO4中电解水制氢的催化活性,活性大小为Pt > Au >> GC。水中离子液体的含量对析氢电流影响很大,当[ HMIm] HSO4含量为30%(V/V)时,Pt电极催化电解水产氢的阈值电位高达-0.3 V (Ag丝为准参比电极, Ag QRE),在-0.5 V (Ag QRE)处电流密度高达110.52 mA/cm2,为相同条件下Au电极的15倍,GC电极的650倍。计算结果表明,Pt电极在该电解液中的反应活化能为5.68 kJ/mol。电极的高催化活性与[ HMIm] HSO4电离产生的质子有关,使水以H3 O+的形式捕集电子,效率更高。     

Controllable deposition of a platinum nanoparticle ensemble on a polyaniline/graphene hybrid as a novel electrode material for electrochemical sensing

We demonstrate for the first time an interfacial polymerization method for the synthesis of high-quality polyaniline-modified graphene nanosheets (PANI/GNs), which represents a novel type of graphene/polymer heterostructure. The interfacial polymerization at a liquid-liquid interface allows PANI to grow uniformly on the surface of the GNs. An ultra-high loading of Pt nanoparticles was then controllably deposited on the surface of the PANI/GNs to form a Pt/PANI/GNs hybrid. The obtained composites were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The Pt/PANI/GNs hybrid shows excellent electrocatalytic activity toward methanol oxidation and oxygen reduction. H(2)O(2) and glucose were used as two representative analytes to demonstrate the sensing performance of a Pt/PANI/GNs-modified electrode. It is found that this sensing element shows high sensitivity and a low detection limit for H(2)O(2) and glucose. The results demonstrate that the Pt/PANI/GNs hybrid may be an attractive and advanced electrode material with potential applications in the construction of electrochemical sensors and biosensors.     

Influence of lanthanum on morphology and electrochemical performance of nano-platinum-based catalytic membrane electrode

The current research of platinum (Pt)–based catalysts focuses on reducing Pt loading in the catalysts while enhancing the catalytic activity. As a rare-earth element, lanthanum (La) has demonstrated good synergistic effect with Pt-based catalysts, because of its catalytic promoting capability and high dispersibility. Here, we fabricated La-doped nano-Pt-based catalytic membrane electrode using ion beam sputtering method. The effect of La on the morphology and electrochemical performance of the catalytic membrane electrode was investigated by scanning electron microscope, X-ray photoelectron spectroscopy, and electrochemical measurements. Compared with pure Pt-based sample, the electrochemical activity specific area of the La-doped sample increases by 74.59%, with 63.95% increase in exchange current density. The results also show that La₂O₃ enhances oxygen enrichment of the membrane electrode and reduces interfacial energy among Pt grains while pinning the grain boundaries. In addition, the inductively coupled plasma atomic emission spectroscopy (ICP-AES) measurement shows that the Pt loading in the membrane electrodes is below 0.1 mg/cm². Thus, enhanced catalytic performance is achieved in catalysts with lower Pt loading.