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1.
Replacing the sluggish oxygen evolution reaction (OER) with oxidation reactions for the synthesis of complex pharmaceutical molecules coupled with enhanced hydrogen evolution reaction (HER) is highly attractive, but it is rarely explored. Here, we report an electrochemical protocol for selective oxidation of sulfides to sulfoxides over a CoFe layered double hydroxide (CoFe-LDH) anode in an aqueous-MeCN electrolyte, coupled with 2-fold promoted cathodic H2 productivity. This protocol displays high activity (85–96% yields), catalyst stability (10 cycles), and generality (12 examples) in selective sulfide oxidation. We demonstrate its applicability in the synthesis of four important pharmaceutical related sulfoxide compounds with scalability (up to 1.79 g). X-ray spectroscopy investigations reveal that the CoFe-LDH material evolved into amorphous CoFe-oxyhydroxide under catalytic conditions. This work may pave the way towards sustainable organic synthesis of valuable pharmaceuticals coupled with H2 production.Replacing anodic OER with selective sulfide oxidation produces sulfoxide-related pharmaceutical compounds over a CoFe-LDH catalyst with enhanced HER, providing a sustainable protocol for valuable pharmaceuticals synthesis without external oxidants. 相似文献
2.
Guoqiang Shen Rongrong Zhang Lun Pan Fang Hou Yingjie Zhao Zeyu Shen Wenbo Mi Chengxiang Shi Qingfa Wang Xiangwen Zhang Ji‐Jun Zou 《Angewandte Chemie (International ed. in English)》2020,59(6):2313-2317
Ferric oxides and (oxy)hydroxides, although plentiful and low‐cost, are rarely considered for oxygen evolution reaction (OER) owing to the too high spin state (eg filling ca. 2.0) suppressing the bonding strength with reaction intermediates. Now, a facile adsorption–oxidation strategy is used to anchor FeIII atomically on an ultrathin TiO2 nanobelt to synergistically lower the spin state (eg filling ca. 1.08) to enhance the adsorption with oxygen‐containing intermediates and improve the electro‐conductibility for lower ohmic loss. The electronic structure of the catalyst is predicted by DFT calculation and perfectly confirmed by experimental results. The catalyst exhibits superior performance for OER with overpotential 270 mV @10 mA cm?2 and 376 mV @100 mA cm?2 in alkaline solution, which is much better than IrO2/C and RuO2/C and is the best iron‐based OER catalyst free of active metals such as Ni, Co, or precious metals. 相似文献
3.
Zhenhua Yan Huanhuan Liu Zhimeng Hao Meng Yu Xiang Chen Jun Chen 《Chemical science》2020,11(39):10614
Electrochemical water splitting is a promising technology for hydrogen production and sustainable energy conversion, but the electrolyzers that are currently available do not have anodic electrodes that are robust enough and highly active for the oxygen evolution reaction (OER). Electrodeposition provides a feasible route for preparing freestanding OER electrodes with high active site utilization, fast mass transport and a simple fabrication process, which is highly attractive from both academic and commercial points of view. This minireview focuses on the recent electrodeposition strategies for metal (hydro)oxide design and water oxidation applications. First, the intrinsic advantages of electrodeposition in comparison with traditional technologies are introduced. Then, the unique properties and underlying principles of electrodeposited metal (hydro)oxides in the OER are unveiled. In parallel, illustrative examples of the latest advances in materials structural design, controllable synthesis, and mechanism understanding through the electrochemical synthesis of (hydro)oxides are presented. Finally, the latest representative OER mechanism and electrodeposition routes for OER catalysts are briefly overviewed. Such observations provide new insights into freestanding (hydro)oxides electrodes prepared via electrodeposition, which show significant practical application potential in water splitting devices. We hope that this review will provide inspiration for researchers and stimulate the development of water splitting technology.This minireview looks at recent electrodeposition strategies for metal (hydro)oxide design and water oxidation applications, unveiling the unique properties and underlying principles of electrodeposited metal (hydro)oxides in the OER. 相似文献
4.
Jiayi Chen Peixin Cui Guoqiang Zhao Kun Rui Mengmeng Lao Yaping Chen Xusheng Zheng Yinzhu Jiang Hongge Pan Shi Xue Dou Wenping Sun 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(36):12670-12674
Highly active and durable electrocatalysts for the oxygen evolution reaction (OER) is greatly desired. Iridium oxide/graphitic carbon nitride (IrO2/GCN) heterostructures are designed with low‐coordinate IrO2 nanoparticles (NPs) confined on superhydrophilic highly stable GCN nanosheets for efficient acidic OER. The GCN nanosheets not only ensure the homogeneous distribution and confinement of IrO2 NPs but also endows the heterostructured catalyst system with a superhydrophilic surface, which can maximize the exposure of active sites and promotes mass diffusion. The coordination number of Ir atoms is decreased owing to the strong interaction between IrO2 and GCN, leading to lattice strain and increment of electron density around Ir sites and hence modulating the attachment between the catalyst and reaction intermediates. The optimized IrO2/GCN heterostructure delivers not only by far the highest mass activity among the reported IrO2‐based catalysts but also decent durability. 相似文献
5.
Carlota Bozal-Ginesta Camilo A. Mesa Annika Eisenschmidt Laia Francs Ravi B. Shankar Daniel Antn-García Julien Warnan Janina Willkomm Anna Reynal Erwin Reisner James R. Durrant 《Chemical science》2021,12(3):946
Multi-redox catalysis requires the accumulation of more than one charge carrier and is crucial for solar energy conversion into fuels and valuable chemicals. In photo(electro)chemical systems, however, the necessary accumulation of multiple, long-lived charges is challenged by recombination with their counterparts. Herein, we investigate charge accumulation in two model multi-redox molecular catalysts for proton and CO2 reduction attached onto mesoporous TiO2 electrodes. Transient absorption spectroscopy and spectroelectrochemical techniques have been employed to study the kinetics of photoinduced electron transfer from the TiO2 to the molecular catalysts in acetonitrile, with triethanolamine as the hole scavenger. At high light intensities, we detect charge accumulation in the millisecond timescale in the form of multi-reduced species. The redox potentials of the catalysts and the capacity of TiO2 to accumulate electrons play an essential role in the charge accumulation process at the molecular catalyst. Recombination of reduced species with valence band holes in TiO2 is observed to be faster than microseconds, while electron transfer from multi-reduced species to the conduction band or the electrolyte occurs in the millisecond timescale. Finally, under light irradiation, we show how charge accumulation on the catalyst is regulated as a function of the applied bias and the excitation light intensity.Using transient spectroelectrochemical techniques, we investigate multiply reduced states of molecular catalysts on titania photoelectrodes as a function of the applied bias and the light intensity. 相似文献
6.
Hiromu Fuse Hiroyasu Nakao Yutaka Saga Arisa Fukatsu Mio Kondo Shigeyuki Masaoka Harunobu Mitsunuma Motomu Kanai 《Chemical science》2020,11(44):12206
Hydroxyalkylation of N-heteroaromatics with aldehydes was achieved using a binary hybrid catalyst system comprising an acridinium photoredox catalyst and a thiophosphoric acid organocatalyst. The reaction proceeded through the following sequence: (1) photoredox-catalyzed single-electron oxidation of a thiophosphoric acid catalyst to generate a thiyl radical, (2) cleavage of the formyl C–H bond of the aldehyde substrates by a thiyl radical acting as a hydrogen atom transfer catalyst to generate acyl radicals, (3) Minisci-type addition of the resulting acyl radicals to N-heteroaromatics, and (4) a spin-center shift, photoredox-catalyzed single-electron reduction, and protonation to produce secondary alcohol products. This metal-free hybrid catalysis proceeded under mild conditions for a wide range of substrates, including isoquinolines, quinolines, and pyridines as N-heteroaromatics, as well as both aromatic and aliphatic aldehydes, and tolerated various functional groups. The reaction was applicable to late-stage derivatization of drugs and their leads.Hydroxyalkylation of N-heteroaromatics with aldehydes was achieved using a binary hybrid catalyst system comprising an acridinium photoredox catalyst and a thiophosphoric acid organocatalyst. 相似文献
7.
Yusuke Kita Midori Kuwabara Satoshi Yamadera Keigo Kamata Michikazu Hara 《Chemical science》2020,11(36):9884
Heterogeneously catalysed synthesis of primary amines by direct amination of alcohols with ammonia has long been an elusive goal. In contrast to reported Ru-based catalytic systems, we report that Ru–MgO/TiO2 acts as an effective heterogeneous catalyst for the direct amination of a variety of alcohols to primary amines at low temperatures of ca. 100 °C without the introduction of H2 gas. The present system could be applied to a variety of alcohols and provides an efficient synthetic route for 2,5-bis(aminomethyl)furan (BAMF), an attention-getting biomonomer. The high catalytic performance can be rationalized by the reactivity tuning of Ru–H species using MgO. Spectroscopic measurements suggest that MgO enhances the reactivity of hydride species by electron donation from MgO to Ru.Ru–MgO/TiO2 exhibited high catalytic performance for direct amination of alcohols based on the acceleration effects of MgO. 相似文献
8.
Nina-Luisa Michels Agnieszka Kapałka A.A. Abd-El-Latif Helmut Baltruschat Christos Comninellis 《Electrochemistry communications》2010,12(9):1199-1202
Electrochemical oxidation of ammonia (NH3 and NH4 + ) on boron-doped diamond (BDD) electrode was studied using differential electrochemical mass-spectrometry (DEMS) and chronoamperometry. Electro-oxidation of ammonia induces inhibition of the oxygen evolution reaction (OER) due to adsorption of the ammonia oxidation products on the BDD surface. The inhibition of the OER enhances ammonia electro-oxidation, which becomes the main reaction. The amino radicals, formed during ammonia oxidation, trigger a reaction chain in which molecular oxygen dissolved in solution is involved in the ammonia electro-oxidation. Nitrogen, nitrous oxide, and nitrogen dioxide were detected as the ammonia oxidation products, with nitrogen being the main gaseous product of the oxidation. 相似文献
9.
Stéphane Fierro Agnieszka Kapałka Christos Comninellis 《Electrochemistry communications》2010,12(1):172-174
The surface redox activities, the oxygen evolution reaction (OER), the oxidation of formic acid (FA) and the anodic stability have been investigated and compared on IrO2 electrodes prepared by two techniques: the thermal decomposition of H2IrCl6 precursor (TDIROF) and the thermal treatment of metallic iridium (TOIROF). It was found, that the surface redox activities involved on both IrO2-based electrodes are similar. Concerning the oxygen evolution reaction and the oxidation of formic acid, both films show similar mechanism.The electrode stability measurements have shown that both films are not corroded under strong OER or organics oxidation conditions and therefore, to summarize, both IrO2-based films exhibit similar electrochemical behaviours. 相似文献
10.
Dr. Hui Chen Lei Shi Xiao Liang Lina Wang Prof. Tewodros Asefa Prof. Xiaoxin Zou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(44):19822-19826
Reducing the amount of iridium in oxygen evolution electrocatalysts without compromising their catalytic performances is one of the major requirements in proton-exchange-membrane water electrolyzers. Herein, with the help of theoretical studies, we show that anatase-type TiO2-IrO2 solid solutions possess more active iridium catalytic sites for the oxygen evolution reaction (OER) than IrO2, the benchmark OER catalyst. Note that the same is not observed for their rutile-type counterparts. However, owing to their thermodynamic metastability, anatase-type TiO2-IrO2 solid solutions are generally hard to synthesize. Our theoretical studies demonstrate that such catalytically active anatase-type solid-solution phases can be created in situ on the surfaces of readily available SrTiO3-SrIrO3 solid solutions during electrocatalysis in acidic solution as the solution can etch away Sr atoms. We experimentally show this with porous SrTiO3-SrIrO3 solid-solution nanotubes synthesized by a facile synthetic route that contain 56 % less iridium than IrO2 yet show an order of magnitude higher apparent catalytic activity for OER in acidic solution. 相似文献
11.
Dye-sensitised photoanodes modified with a water oxidation catalyst allow for solar-driven O2 evolution in photoelectrochemical cells. However, organic chromophores are generally considered unsuitable to drive the thermodynamically demanding water oxidation reaction, mainly due to their lack of stability upon photoexcitation. Here, the synthesis of a dyad photocatalyst (DPP-Ru) consisting of a diketopyrrolopyrrole chromophore (DPPdye) and ruthenium-based water oxidation catalyst (RuWOC) is described. The DPP-Ru dyad features a cyanoacrylic acid anchoring group for immobilisation on metal oxides, strong absorption in the visible region of the electromagnetic spectrum, and photoinduced hole transfer from the dye to the catalyst unit. Immobilisation of the dyad on a mesoporous TiO2 scaffold was optimised, including the use of a TiCl4 pretreatment method as well as employing chenodeoxycholic acid as a co-adsorbent, and the assembled dyad-sensitised photoanode achieved O2 evolution using visible light (100 mW cm−2, AM 1.5G, λ > 420 nm). An initial photocurrent of 140 μA cm−2 was generated in aqueous electrolyte solution (pH 5.6) under an applied potential of +0.2 V vs. NHE. The production of O2 has been confirmed by controlled potential electrolysis with a faradaic efficiency of 44%. This study demonstrates that metal-free dyes are suitable light absorbers in dyadic systems for the assembly of water oxidising photoanodes.Construction of a water oxidising photoanode with an organic chromophore-catalyst dyad. 相似文献
12.
Katherine J. Lee Kunal M. Lodaya Cole T. Gruninger Eric S. Rountree Jillian L. Dempsey 《Chemical science》2020,11(36):9836
The solubility of molecular transition metal complexes can vary widely across different redox states, leaving these compounds vulnerable to electron transfer-initiated heterogenization processes in which oxidation or reduction of the soluble form of the redox couple generates insoluble molecular deposits. These insoluble species can precipitate as suspended nanoparticles in solution or, under electrochemical conditions, as an electrode-adsorbed material. While this electrochemically-driven solubility cycling is technically reversible, the reverse electron transfer to regenerate the soluble redox couple state is a practical challenge if sluggish electron transfer kinetics result in a loss of electronic communication between the molecular deposits and the electrode. In this work, we present an example of this electrochemically-driven solubility cycling, report a novel strategy for catalytically enhancing the oxidation of the insoluble material using homogeneous redox mediators, and develop the theoretical framework for analysing and digitally simulating the action of a homogeneous catalyst on a heterogeneous substrate via cyclic voltammetry. First, a mix of electrochemical and spectroscopic methods are used to characterize an example of this electrochemically-driven solubility cycling which is based on the two-electron reduction of homogeneous [Ni(PPh2NPh2)2(CH3CN)]2+ (PPh2NPh2 = 1,3,5,7-tetraphenyl-1,5-diaza-3,7-diphosphacyclooctane). The limited solubility of the doubly-reduced product in acetonitrile leads to precipitation and deposition of molecular [Ni(PPh2NPh2)2]. While direct oxidation of this heterogeneous [Ni(PPh2NPh2)2] at the electrode surface is possible, this electron transfer is kinetically limited. We demonstrate how a freely diffusing redox mediator (ferrocene) – which shuttles electrons between the electrode and the molecular material – can be used to overcome these slow electron transfer kinetics, enabling catalytic regeneration of soluble [Ni(PPh2NPh2)2]2+. Finally, mathematical models are developed that describe the current–potential response for a generic EC′ mechanism involving a homogeneous catalyst and surface-adsorbed substrate. This novel strategy has the potential to enable reversible redox chemistry for heterogeneous, molecular deposits that are adsorbed on the electrode or suspended as nanoparticles in solution.We present an example of electrochemically-driven solubility cycling of a molecular transition metal complex and report a novel strategy for catalytically enhancing the oxidation of an insoluble material using homogeneous redox mediators. 相似文献
13.
Gold is noble in bulk but turns out to be a superior catalyst at the nanoscale when supported on oxides, in particular titania. The critical thickness for activity, namely two-layer gold particles on titania, observed two decades ago represents one of the most influential mysteries in the recent history of heterogeneous catalysis. By developing a Bayesian optimization controlled global potential energy surface exploration tool with machine learning potential, here we determine the atomic structures of gold particles within ∼2 nm on a TiO2 surface. We show that the smallest stable Au nanoparticle is Au24 which is pinned on the oxygen-rich TiO2 and exhibits an unprecedented dome architecture made by a single-layer Au sheet but with an apparent two-atomic-layer height. Importantly, this has the highest activity for CO oxidation at room temperature. The physical origin of the high activity is the outstanding electron storage ability of the nano-dome, which activates the lattice oxygen of the oxide. The determined CO oxidation mechanism, the simulated rate and the fitted apparent energy barrier are consistent with known experimental facts, providing key evidence for the presence of both the high-activity Au dome and the low-activity close-packed Au particles in real catalysts. The future direction for the preparation of active and stable Au-based catalysts is thus outlined.The smallest stable Au particle Au24O4 on TiO2 surface is determined by the machine learning assisted global optimization, exhibiting a dome architecture made by a single-layer sheet and the highest activity for CO oxidation at room temperature. 相似文献
14.
Xuanbei Peng Han-Xuan Liu Yangyu Zhang Zheng-Qing Huang Linlin Yang Yafei Jiang Xiuyun Wang Lirong Zheng Chunran Chang Chak-tong Au Lilong Jiang Jun Li 《Chemical science》2021,12(20):7125
The desire for a carbon-free society and the continuously increasing demand for clean energy make it valuable to exploit green ammonia (NH3) synthesis that proceeds via the electrolysis driven Haber–Bosch (eHB) process. The key for successful operation is to develop advanced catalysts that can operate under mild conditions with efficacy. The main bottleneck of NH3 synthesis under mild conditions is the known scaling relation in which the feasibility of N2 dissociative adsorption of a catalyst is inversely related to that of the desorption of surface N-containing intermediate species, which leads to the dilemma that NH3 synthesis could not be catalyzed effectively under mild conditions. The present work offers a new strategy via introducing atomically dispersed Ru onto a single Co atom coordinated with pyrrolic N, which forms RuCo dual single-atom active sites. In this system the d-band centers of Ru and Co were both regulated to decouple the scaling relation. Detailed experimental and theoretical investigations demonstrate that the d-bands of Ru and Co both become narrow, and there is a significant overlapping of t2g and eg orbitals as well as the formation of a nearly uniform Co 3d ligand field, making the electronic structure of the Co atom resemble that of a “free-atom”. The “free-Co-atom” acts as a bridge to facilitate electron transfer from pyrrolic N to surface Ru single atoms, which enables the Ru atom to donate electrons to the antibonding π* orbitals of N2, thus resulting in promoted N2 adsorption and activation. Meanwhile, H2 adsorbs dissociatively on the Co center to form a hydride, which can transfer to the Ru site to cause the hydrogenation of the activated N2 to generate N2Hx (x = 1–4) intermediates. The narrow d-band centers of this RuCo catalyst facilitate desorption of surface *NH3 intermediates even at 50 °C. The cooperativity of the RuCo system decouples the sites for the activation of N2 from those for the desorption of *NH3 and *N2Hx intermediates, giving rise to a favorable pathway for efficient NH3 synthesis under mild conditions.The desire for a carbon-free society and the continuously increasing demand for clean energy make it valuable to exploit green ammonia (NH3) synthesis that proceeds via the electrolysis driven Haber–Bosch (eHB) process. 相似文献
15.
A chiral N,N′-dioxide/cobalt(ii) complex catalyzed highly diastereoselective and enantioselective tandem aza-Piancatelli rearrangement/intramolecular Diels–Alder reaction has been disclosed. Various valuable hexahydro-2a,5-epoxycyclopenta[cd]isoindoles bearing six contiguous stereocenters have been obtained in good yields with excellent diastereo- and enantio-selectivities from a wide range of both readily available 2-furylcarbinols and N-(furan-2-ylmethyl)anilines.An asymmetric aza-Piancatelli rearrangement/Diels–Alder cascade reaction between 2-furylcarbinols and N-(furan-2-ylmethyl)anilines was realized by using a chiral N,N′-dioxide/cobalt(ii) complex catalyst. 相似文献
16.
Suresh C. Rathnayaka Shahidul M. Islam Ida M. DiMucci Samantha N. MacMillan Kyle M. Lancaster Neal P. Mankad 《Chemical science》2020,11(13):3441
Nitrous oxide (N2O) contributes significantly to ozone layer depletion and is a potent greenhouse agent, motivating interest in the chemical details of biological N2O fixation by nitrous oxide reductase (N2OR) during bacterial denitrification. In this study, we report a combined experimental/computational study of a synthetic [4Cu:1S] cluster supported by N-donor ligands that can be considered the closest structural and functional mimic of the CuZ catalytic site in N2OR reported to date. Quantitative N2 measurements during synthetic N2O reduction were used to determine reaction stoichiometry, which in turn was used as the basis for density functional theory (DFT) modeling of hypothetical reaction intermediates. The mechanism for N2O reduction emerging from this computational modeling involves cooperative activation of N2O across a Cu/S cluster edge. Direct interaction of the μ4-S ligand with the N2O substrate during coordination and N–O bond cleavage represents an unconventional mechanistic paradigm to be considered for the chemistry of CuZ and related metal–sulfur clusters. Consistent with hypothetical participation of the μ4-S unit in two-electron reduction of N2O, Cu K-edge and S K-edge X-ray absorption spectroscopy (XAS) reveal a high degree of participation by the μ4-S in redox changes, with approximately 21% S 3p contribution to the redox-active molecular orbital in the highly covalent [4Cu:1S] core, compared to approximately 14% Cu 3d contribution per copper. The XAS data included in this study represent the first spectroscopic interrogation of multiple redox levels of a [4Cu:1S] cluster and show high fidelity to the biological CuZ site.Experimental data and computational modeling indicates an active role for the bridging sulfide ligand in a synthetic CuZ model. 相似文献
17.
Kathiravan Murugesan Zhihong Wei Vishwas G. Chandrashekhar Haijun Jiao Matthias Beller Rajenahally V. Jagadeesh 《Chemical science》2020,11(17):4332
The development of base metal catalysts for industrially relevant amination and hydrogenation reactions by applying abundant and atom economical reagents continues to be important for the cost-effective and sustainable synthesis of amines which represent highly essential chemicals. In particular, the synthesis of primary amines is of central importance because these compounds serve as key precursors and central intermediates to produce value-added fine and bulk chemicals as well as pharmaceuticals, agrochemicals and materials. Here we report a Ni-triphos complex as the first Ni-based homogeneous catalyst for both reductive amination of carbonyl compounds with ammonia and hydrogenation of nitroarenes to prepare all kinds of primary amines. Remarkably, this Ni-complex enabled the synthesis of functionalized and structurally diverse benzylic, heterocyclic and aliphatic linear and branched primary amines as well as aromatic primary amines starting from inexpensive and easily accessible carbonyl compounds (aldehydes and ketones) and nitroarenes using ammonia and molecular hydrogen. This Ni-catalyzed reductive amination methodology has been applied for the amination of more complex pharmaceuticals and steroid derivatives. Detailed DFT computations have been performed for the Ni-triphos based reductive amination reaction, and they revealed that the overall reaction has an inner-sphere mechanism with H2 metathesis as the rate-determining step.A Ni-triphos based homogeneous catalyst enabled the synthesis of all kinds of primary amines by reductive amination of carbonyl compounds with ammonia and hydrogenation of nitroarenes. 相似文献
18.
通过Adams方法成功制备MnO2-0.39IrOx(0.39为Ir/Mn的原子比)催化剂并将其用于酸性介质中高效析氧反应(OER)。电化学测试发现,MnO2-0.39IrOx仅需253 mV的过电势即可驱动10 mA·cm-2的水氧化电流密度,并可稳定运行200 h。在1.50 V(vs RHE)电势下,MnO2-0.39IrOx的贵金属Ir的质量活性为61.3 mA·mg-1,是IrO2的35.8倍,说明MnO2掺杂大大提升了贵金属利用率。结构分析发现MnO2-0.39IrOx独特的片状结构大幅度提高了催化剂的电化学活性表面积,并且Ir位点与Mn位点之间存在一定的电子相互作用。催化过程分析表明,MnO2-0.39IrOx表面出现一定的重构现象,并且Mn组分对Ir位点的化学环境实现了持续优化,从而实现了催化剂的高效酸性OER性能。 相似文献
19.
Laia Francs Shababa Selim Sacha Corby Dongho Lee Camilo A. Mesa Ernest Pastor Kyoung-Shin Choi James R. Durrant 《Chemical science》2021,12(21):7442
In this work, spectroelectrochemical techniques are employed to analyse the catalytic water oxidation performance of a series of three nickel/iron oxyhydroxide electrocatalysts deposited on FTO and BiVO4, at neutral pH. Similar electrochemical water oxidation performance is observed for each of the FeOOH, Ni(Fe)OOH and FeOOHNiOOH electrocatalysts studied, which is found to result from a balance between degree of charge accumulation and rate of water oxidation. Once added onto BiVO4 photoanodes, a large enhancement in the water oxidation photoelectrochemical performance is observed in comparison to the un-modified BiVO4. To understand the origin of this enhancement, the films were evaluated through time-resolved optical spectroscopic techniques, allowing comparisons between electrochemical and photoelectrochemical water oxidation. For all three catalysts, fast hole transfer from BiVO4 to the catalyst is observed in the transient absorption data. Using operando photoinduced absorption measurements, we find that water oxidation is driven by oxidised states within the catalyst layer, following hole transfer from BiVO4. This charge transfer is correlated with a suppression of recombination losses which result in remarkably enhanced water oxidation performance relative to un-modified BiVO4. Moreover, despite similar electrocatalytic behaviour of all three electrocatalysts, we show that variations in water oxidation performance observed among the BiVO4/MOOH photoanodes stem from differences in photoelectrochemical and electrochemical charge accumulation in the catalyst layers. Under illumination, the amount of accumulated charge in the catalyst is driven by the injection of photogenerated holes from BiVO4, which is further affected by the recombination loss at the BiVO4/MOOH interface, and thus leads to deviations from their behaviour as standalone electrocatalysts.Elucidating the role of charge accumulation and reaction kinetics in governing the performance of Ni/Fe oxyhydroxides as electrocatalysts and as co-catalysts on BiVO4 photoanodes water oxidation. 相似文献
20.
Yong Zhu Guoquan Liu Ran Zhao Hua Gao Xiaona Li Licheng Sun Fei Li 《Chemical science》2022,13(17):4955
Artificial photosynthesis provides a way to store solar energy in chemical bonds with water oxidation as a major challenge for creating highly efficient and robust photoanodes that mimic photosystem II. We report here an easily available pyridine N-oxide (PNO) derivative as an efficient electron transfer relay between an organic light absorber and molecular water oxidation catalyst on a nanoparticle TiO2 photoanode. Spectroscopic and kinetic studies revealed that the PNO/PNO+˙ couple closely mimics the redox behavior of the tyrosine/tyrosyl radical pair in PSII in improving light-driven charge separation via multi-step electron transfer. The integrated photoanode exhibited a 1 sun current density of 3 mA cm−2 in the presence of Na2SO3 and a highly stable photocurrent density of >0.5 mA cm−2 at 0.4 V vs. NHE over a period of 1 h for water oxidation at pH 7. The performance shown here is superior to those of previously reported organic dye-based photoanodes in terms of photocurrent and stability.Stable and high photocurrent for water oxidation was achieved by an organic dye-sensitized photoanode with a pyridine N-oxide derivative as an efficient electron relay between the chromophore and molecular water oxidation catalyst. 相似文献