Surface Of Heterogeneous Catalysts Research Articles

A kinetic study to test silver nanoparticle/chitosan architecture on heterogeneous catalyst surface

The catalyst building-up is studied with the goal of assessing effective procedures which lead to optimal performance devices. Tailor-made copolymeric networks of ethylene glycol di-methacrylate and 2-hydroxyethyl methacrylate (EGDMA-HEMA) and the composite of silver nanoparticle / chitosan (AgNP/CS) were separately synthesized and used to build-up heterogeneous catalysts. The AgNP/CS composite adsorption is controlled by the hydroxyl-group content within the platform surface, since changing this factor leads to monolayer or multilayer architectures to be obtained. Complementary to characterization techniques (immobilization degree, contact angle and SEM), a kinetic study of catalyst behavior is used as at testing surface architectures. The overall kinetics of 4-nitrophenol reduction with sodium borohydride is governed by the conversion process on AgNP and the matter transport through surface chitosan architecture. Consistently, multilayer architectures behave as a flux-resistant structure and their kinetics obey this general description, raising the activation energy up to ∼61 KJ.mol−1. For temperatures over 35 °C, monolayer architectures kinetically behave as solely governed by the conversion process on AgNP and its intrinsic activation energy is estimated in 14 KJ.mol−1.

Spectra-Based Machine Learning for Predicting the Statistical Interaction Properties of CO Adsorbates on Surface.

Theoretical analyses of small-molecule adsorption on heterogeneous catalyst surfaces often rely on simplified models of molecular adsorption with the most favorable configuration. Given that real-world experimental tests frequently entail multiple molecules interacting with the surface, there is a pressing need for a comprehensive multimolecule adsorption model to bridge the gap between theory and experiment. Using machine learning, we predict the average values of important adsorption properties from conformationally averaged, calculated infrared and Raman spectra and compare these values to those theoretically derived from the conformationally averaged ensemble. Remarkably, our approach yields excellent predictions even when faced with large and indeterminate numbers of surface molecules. These quantitative spectra-averaged property relationships provide a theoretical framework for extracting key interaction properties from the spectra of real chemical environments.

Probing Catalytic Sites and Adsorbate Spillover on Ultrathin FeO2-x Film on Ir(111) during CO Oxidation.

The spatially resolved identification of active sites on the heterogeneous catalyst surface is an essential step toward directly visualizing a catalytic reaction with atomic scale. To date, ferrous centers on platinum group metals have shown promising potential for low-temperature CO catalytic oxidation, but the temporal and spatial distribution of active sites during the reaction and how molecular-scale structures develop at the interface are not fully understood. Here, we studied the catalytic CO oxidation and the effect of co-adsorbed hydrogen on the FeO2-x/Ir(111) surface. Combining scanning tunneling microscopy (STM), isotope-labeled pulse reaction measurements, and DFT calculations, we identified both FeO2/Ir and FeO2/FeO sites as active sites with different reactivity. The trilayer O-Fe-O structure with its Moiré pattern can be fully recovered after O2 exposure, where molecular O2 dissociates at the FeO/Ir interface. Additionally, as a competitor, dissociated hydrogen migrates onto the oxide film with the formation of surface hydroxyl and water clusters down to 150 K.

Flexible and Extensive Platinum Ion Gel Condensers for Programmable Catalysis.

Catalytic condensers composed of ion gels separating a metal electrode from a platinum-on-carbon active layer were fabricated and characterized to achieve more powerful, high surface area dynamic heterogeneous catalyst surfaces. Ion gels comprised of poly(vinylidene difluoride)/1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide were spin coated as a 3.8 μm film on a Au surface, after which carbon sputtering of a 1.8 nm carbon film and electron-beam evaporation of 2 nm Pt clusters created an active surface exposed to reactant gases. Electronic characterization indicated that most charge condensed within the Pt nanoclusters upon application of a potential bias, with the condenser device achieving a capacitance of ∼20 μF/cm2 at applied frequencies of up to 120 Hz. The maximum charge of ∼1014 |e-| cm-2 was condensed under stable device conditions at 200 °C on catalytic films with ∼1015 sites cm-2. Grazing incidence infrared spectroscopy measured carbon monoxide adsorption isobars, indicating a change in the CO* binding energy of ∼19 kJ mol-1 over an applied potential bias of only 1.25 V. Condensers were also fabricated on flexible, large area Kapton substrates allowing stacked or tubular form factors that facilitate high volumetric active site densities, ultimately enabling a fast and powerful catalytic condenser that can be fabricated for programmable catalysis applications.

(Invited) Nucleation, Growth and Location Regulation of Heterogeneous Catalysts Synthesized by Atomic Layer Deposition

For supported catalysts, the particle surface or metal-support interface and its vicinity are the main areas providing active sites. In this regard, surface and interface engineering of heterogeneous catalysts is effective and critical for optimizing their catalytic performances. During the formation of active components, the structural uniformity, stability and location of nucleation sites determine the structural and scale uniformity, stability and environmental consistency of active sites, and ultimately determine their catalytic performance. Therefore, the regulation of nucleation, growth and location of active components is the key to precisely regulate the surface and interface structure and properties of supported catalysts. However, traditional preparation methods (such as impregnation method and precipitation method) have limitations in precise regulation of particle size, location and microstructure of catalysts due to the surface heterogeneity of supports and the high surface energy of nanoparticles, which makes it difficult to reliably reveal the structure-activity relationship of the catalyst. Therefore, the development of advanced fabrication methods is of vital significance to realize the nucleation, growth and location regulation of heterogeneous catalysts at atomic level precision. Atomic layer deposition (ALD) is a powerful scientific tool for catalytic research due to its self-limiting, atom-by-atom growth features. However, there is still a lack of rational knowledge of the nucleation and growth mechanism of catalytic particles prepared by ALD, the microscopic mechanism of interface structure modification, and the catalytic reaction mechanism. This is the topic of this lecture, in which we discuss the latest progress made in our group in precisely regulating the microstructure, size and location of ALD-deposited active components by several effective methods including nucleation site engineering, deposition kinetics engineering and template-assisted ALD method, as well as elucidating the nucleation and growth mechanism of ALD-deposited active components by in-situ and operando XAFS characterization based on our designed and built ALD-XAFS device. Through the above works, the nucleation and growth mechanisms of the deposited species and modification species, the microscopic mechanism of interface structure modification, and the influence of the size effect, the interface effect, and the distance effect on the catalytic performance were clarified. The structure-activity relationship was understood at the atomic/molecular level. These works will provide new ideas and scientific basis for the catalyst design and the performance regulation.

METAL-BASED REUSABLE CATALYSTS FOR PHOTOREDUCTION OF CO2 TO FUELS: FUNDAMENTALS AND RECENT DEVELOPMENTS

CO<sub>2</sub> photoreduction into solar fuels is supposed to be one of the finest approaches to simultaneously dealing with global warming and energy shortage. Low photoconversion efficiency and low selectivity toward target products are the major challenges for CO<sub>2</sub> photoreduction. To counter these challenges it is necessary to develop cost-effective, stable, and highly active photocatalysts. Metal-based materials having tunable band gaps, high stability, and excellent physicochemical and electrochemical properties attract the attention of researchers and are widely studied as potential photocatalysts. In this review, recent progress in the fundamental understanding of photocatalytic CO<sub>2</sub> reduction on the surface of metal-based heterogeneous catalysts is described. This review summarizes the different methodologies that have been established to date to control product selectivity toward C1 and C2+ products through photocatalysis, emphasizing the most promising approaches. The challenges and outlooks of CO<sub>2</sub> photoreduction over metal-based heterogeneous catalysts are discussed.

Surface and Interface Coordination Chemistry Learned from Model Heterogeneous Metal Nanocatalysts: From Atomically Dispersed Catalysts to Atomically Precise Clusters.

The surface and interface coordination structures of heterogeneous metal catalysts are crucial to their catalytic performance. However, the complicated surface and interface structures of heterogeneous catalysts make it challenging to identify the molecular-level structure of their active sites and thus precisely control their performance. To address this challenge, atomically dispersed metal catalysts (ADMCs) and ligand-protected atomically precise metal clusters (APMCs) have been emerging as two important classes of model heterogeneous catalysts in recent years, helping to build bridge between homogeneous and heterogeneous catalysis. This review illustrates how the surface and interface coordination chemistry of these two types of model catalysts determines the catalytic performance from multiple dimensions. The section of ADMCs starts with the local coordination structure of metal sites at the metal-support interface, and then focuses on the effects of coordinating atoms, including their basicity and hardness/softness. Studies are also summarized to discuss the cooperativity achieved by dual metal sites and remote effects. In the section of APMCs, the roles of surface ligands and supports in determining the catalytic activity, selectivity, and stability of APMCs are illustrated. Finally, some personal perspectives on the further development of surface coordination and interface chemistry for model heterogeneous metal catalysts are presented.

Controlling the Hydrophilicity of the Electrochemical Interface to Modulate the Oxygen-Atom Transfer in Electrocatalytic Epoxidation Reactions.

The electrocatalytic epoxidation of alkenes at heterogeneous catalysts using water as the sole oxygen source is a promising safe route toward the sustainable synthesis of epoxides, which are essential building blocks in organic chemistry. However, the physicochemical parameters governing the oxygen-atom transfer to the alkene and the impact of the electrolyte structure on the epoxidation reaction are yet to be understood. Here, we study the electrocatalytic epoxidation of cyclooctene at the surface of gold in hybrid organic/aqueous mixtures using acetonitrile (ACN) solvent. Gold was selected, as in ACN/water electrolytes gold oxide is formed by reactivity with water at potentials less anodic than the oxygen evolution reaction (OER). This unique property allows us to demonstrate that a sacrificial mechanism is responsible for cyclooctene epoxidation at metallic gold surfaces, proceeding through cyclooctene activation, while epoxidation at gold oxide shares similar reaction intermediates with the OER and proceeds via the activation of water. More importantly, we show that the hydrophilicity of the electrode/electrolyte interface can be tuned by changing the nature of the supporting salt cation, hence affecting the reaction selectivity. At low overpotential, hydrophilic interfaces formed using strong Lewis acid cations are found to favor gold passivation. Instead, hydrophobic interfaces created by the use of large organic cations favor the oxidation of cyclooctene and the formation of epoxide. Our study directly demonstrates how tuning the hydrophilicity of electrochemical interfaces can improve both the yield and selectivity of anodic reactions at the surface of heterogeneous catalysts.

(Invited) Understanding Water Oxidation Mechanisms on Heterogeneous Catalyst Surfaces

Water oxidation is an important first step in photosynthesis. It provides electrons and protons for reduction reactions such as hydrogen generation or carbon dioxide reduction. From a technological development perspective, it is critically important to carry out water oxidation on heterogeneous catalyst surfaces. However, this reaction is exceedingly difficult to study. Part of the reason for the challenge lies in the lack of clarity of the catalytically active centers for water oxidation. Another reason for the difficulty comes from the fact that the structures of the active center often evolve under reaction conditions. These issues have made water oxidation by heterogeneous catalysts poorly understood. In this talk, we present our recent efforts in addressing this challenge. Using cobalt oxide-based catalysts as a model system, we introduced a new approach of varying water activities. This was achieved through a "water-in-salt" electrolyte system. It was observed that such an electrolyte allows for discerning two competing mechanisms of water oxidation, namely water nucleophilic attack and intramolecular oxygen coupling. Moreover, it was found that the mechanisms are sensitive to the driving forces, demonstrating a preferences to water nucleophilic attack at high applied potentials and intramolecular oxygen coupling at low applied potentials. The results have major implications to the catalyst design for water oxidation reactions.

Recent Advances in Carbon Dioxide Adsorption, Activation and Hydrogenation to Methanol using Transition Metal Carbides.

The inevitable emission of carbon dioxide (CO2 ) due to the burning of a substantial amount of fossil fuels has led to serious energy and environmental challenges. Metal-based catalytic CO2 transformations into commodity chemicals are a favorable approach in the CO2 mitigation strategy. Among these transformations, selective hydrogenation of CO2 to methanol is the most promising process that not only fulfils the energy demands but also re-balances the carbon cycle. The investigation of CO2 adsorption on the surface of heterogeneous catalyst is highly important because the formation of various intermediates which determines the selectivity of product. Transition metal carbides (TMCs) have received considerable attention in recent years because of their noble metal-like reactivity, ceramic-like properties, high chemical and thermal stability. These features make them excellent catalytic materials for a variety of transformations such as CO2 adsorption and its conversion into value-added chemicals. Herein, the catalytic properties of TMCs are summarize along with synthetic methods, CO2 binding modes, mechanistic studies, effects of dopant on CO2 adsorption, and carbon/metal ratio in the CO2 hydrogenation reaction to methanol using computational as well as experimental studies. Additionally, this Review provides an outline of the challenges and opportunities for the development of potential TMCs in CO2 hydrogenation reactions.

Exploring Structure-Sensitive Relations for Small Species Adsorption Using Machine Learning.

Accurate prediction of adsorption energies on heterogeneous catalyst surfaces is crucial to predicting reactivity and screening materials. Adsorption linear scaling relations have been developed extensively but often lack accuracy and apply to one adsorbate and a single binding site type at a time. These facts undermine their ability to predict structure sensitivity and optimal catalyst structure. Using machine learning on nearly 300 density functional theory calculations, we demonstrate that generalized coordination number scaling relations hold well for oxygen- and high-valency carbon-binding species but fail for others. We reveal that the valency and the electronic coupling of a species with the surface, along with the site type and its coordination environment, are critical for small species adsorption. The model simultaneously predicts the adsorption energy and preferred site and significantly outperforms linear scalings in accuracy. It can expose the structure sensitivity of chemical reactions and enable enhanced catalyst activity via engineering particle shape and facet defects. The generality of our methodology is validated by training the model with transition metal data and transferring it to predict adsorption energies on single-atom alloys.

Enhanced visible light photocatalytic performance of Sr0.3(Ba,Mn)0.7ZrO3 perovskites anchored on graphene oxide

In search of better materials for visible light photocatalytic performance, perovskite Sr0.3(Ba/Mn)0.7ZrO3 nanopowders anchored on graphene oxide were synthesized for the evaluation of their photocatalytic activity against methylene blue (MB). The chemical coprecipitation method was used to synthesize SrZrO3 (SZO) and a series of doped derivatives having a nominal composition of Sr1-x(Ba,Mn)xZrO3 (x = 0.1–0.9) at an annealing temperature of 700 °C for 12 h. However, Sr0.3(Ba,Mn)0.7ZrO3 with a bandgap value of 3.50 eV was further processed for the formation of composite with graphene oxide (GO) owing to its lowest bandgap value in the synthesized series. The inclusion of larger Ba2+ cations in the lattice resulted in the redistribution of cations creating antisite defects which were evident from the shrinkage of the lattice. The incorporation of Mn2+ resulted in the hybridization of Mn2+ (3d) orbitals with the split Zr4+ (4d) orbitals. This reduced the bandgap and composite formation with GO further enhancing the delocalization of excited electrons to GO hence, reducing electron-hole recombination. Adsorption assisted photocatalysis under a 100 W tungsten lamp was performed using the designed catalysts for the removal/degradation of MB. The π-π conjugation and the ionic interactions were found responsible for the adsorption of MB at the GO surface. High surface coverage, initial dye concentrations, heterogeneous catalyst surface, weak van der Waals interactions, pH and availability of •OH radicals were found to be the decisive factors for the removal/degradation process. Improved charge separation enhances the generation of •OH and better performance of the GO composites as opposed to the pristine strontium zirconate perovskites.

Scalable synthesis of supported catalysts using fluidized bed atomic layer deposition

Overcoating layers deposited on the surface of heterogeneous catalysts using atomic layer deposition (ALD) have been shown to increase catalyst activity, lifetime, and selectivity. In this study, we performed Al2O3 ALD and Pd ALD in a commercial fluidized bed reactor on high surface area mesoporous powder supports to create overcoated catalysts with high precursor utilization. We investigated the reaction mechanism for both Al2O3 ALD and Pd ALD using in situ mass spectrometry and developed a mathematical model to understand the precursor saturation behaviors. We characterized the catalyst samples using a variety of techniques to measure the surface area, porosity, composition, and surface chemistry of the overcoated catalysts. Finally, we used propane dehydrogenation as a probe reaction to evaluate the performance of the catalysts prepared by fluidized bed ALD.

Tuning the Electronic and Steric Interaction at the Atomic Interface for Enhanced Oxygen Evolution.

The two-dimensional surface or one-dimensional interface of heterogeneous catalysts is essential to determine the adsorption strengths and configurations of the reaction intermediates for desired activities. Recently, the development of single-atom catalysts has enabled an atomic-level understanding of catalytic processes. However, it remains obscure whether the conventional concept and mechanism of one-dimensional interface are applicable to zero-dimensional single atoms. In this work, we arranged the locations of single atoms to explore their interfacial interactions for improved oxygen evolution. When iridium single atoms were confined into the lattice of CoOOH, efficient electron transfer between Ir and Co tuned the adsorption strength of oxygenated intermediates. In contrast, atomic iridium species anchored on the surface of CoOOH induced inappreciable modification in electronic structures, whereas steric interactions with key intermediates at its Ir-OH-Co interface played a primary role in reducing its energy barrier toward oxygen evolution.

Sludge-derived biochar toward sustainable Peroxymonosulfate Activation: Regulation of active sites and synergistic production of reaction oxygen species

Active sites on the surface of heterogeneous catalysts accounted for the generation of reactive oxygen species (ROS) from peroxymonosulfate (PMS) toward organic degradation. In this study, the surface chemistry of sewage sludge-derived biochar (SSB) was regulated by controlled pyrolysis and SSB was used for PMS activation and oxidation of antibiotic ciprofloxacin (CIP). SSB-20–120 achieved high CIP removal efficiencies in both batch test (94.2%) and continuous column test (96.3%) with PMS. The species and contents of Fe, N and O as active sites on SSB and their relationships with generated ROS (SO4•−, •OH, and 1O2) for CIP degradation were comprehensively identified. Fe(0), –OH, C = O and the pairwise interaction among Fe(0), Fe(II) and Fe(III) were responsible for SO4•− generation. Besides, pyrrolic N, graphitic N and the co-effect among pyridinic N, pyrrolic N and graphitic N exerted positive effects on •OH and SO4•− generation simultaneously. Meanwhile, Fe(II), Fe(III), pyrrolic N, graphitic N, lattice O with –OH, lattice O with C = O, the interactions among Fe(0), Fe(II) and Fe(III) as well as pyridinic N, pyrrolic N and graphitic N contributed to the production of •OH coupling with 1O2. Moreover, SO4•− and 1O2, as well as the co-effects of •OH with SO4•− and •OH with 1O2 were in favor of CIP degradation. This research provided new insights into the biochar synthesis, structure evolution, and the generation mechanism of reactive oxygen species from PMS activation. Outcomes are beneficial to sewage sludge utilization and developing low-cost catalysts for wastewater remediation.

Stroboscopic operando spectroscopy of the dynamics in heterogeneous catalysis by event-averaging

Heterogeneous catalyst surfaces are dynamic entities that respond rapidly to changes in their local gas environment, and the dynamics of the response is a decisive factor for the catalysts’ action and activity. Few probes are able to map catalyst structure and local gas environment simultaneously under reaction conditions at the timescales of the dynamic changes. Here we use the CO oxidation reaction and a Pd(100) model catalyst to demonstrate how such studies can be performed by time-resolved ambient pressure photoelectron spectroscopy. Central elements of the method are cyclic gas pulsing and software-based event-averaging by image recognition of spectral features. A key finding is that at 3.2 mbar total pressure a metallic, predominantly CO-covered metallic surface turns highly active for a few seconds once the O2:CO ratio becomes high enough to lift the CO poisoning effect before mass transport limitations triggers formation of a √5 oxide.

Dinickel Active Sites Supported by Redox-Active Ligands.

Redox reactions that take place in enzymes and on the surfaces of heterogeneous catalysts often require active sites that contain multiple metals. By contrast, there are very few homogeneous catalysts with multinuclear active sites, and the field of organometallic chemistry continues to be dominated by the study of single metal systems. Multinuclear catalysts have the potential to display unique properties owing to their ability to cooperatively engage substrates. Furthermore, direct metal-to-metal covalent bonding can give rise to new electronic configurations that dramatically impact substrate binding and reactivity. In order to effectively capitalize on these features, it is necessary to consider strategies to avoid the dissociation of fragile metal-metal bonds in the course of a catalytic cycle. This Account describes one approach to accomplishing this goal using binucleating redox-active ligands.In 2006, Chirik showed that pyridine-diimines (PDI) have sufficiently low-lying π* levels that they can be redox-noninnocent in low-valent iron complexes. Extending this concept, we investigated a series of dinickel complexes supported by naphthyridine-diimine (NDI) ligands. These complexes can promote a broad range of two-electron redox processes in which the NDI ligand manages electron equivalents while the metals remain in a Ni(I)-Ni(I) state.Using (NDI)Ni2 catalysts, we have uncovered cases where having two metals in the active site addresses a problem in catalysis that had not been adequately solved using single-metal systems. For example, mononickel complexes are capable of stoichiometrically dimerizing aryl azides to form azoarenes but do not turn over due to strong product inhibition. By contrast, dinickel complexes are effective catalysts for this reaction and avoid this thermodynamic sink by binding to azoarenes in their higher-energy cis form.Dinickel complexes can also activate strong bonds through the cooperative action of both metals. Norbornadiene has a ring-strain energy that is similar to that of cyclopropane but is not prone to undergoing C-C oxidative addition with monometallic complexes. Using an (NDI)Ni2 complex, norbornadiene undergoes rapid ring opening by the oxidative addition of the vinyl and bridgehead carbons. An inspection of the resulting metallacycle reveals that it is stabilized through a network of secondary Ni-π interactions. This reactivity enabled the development of a catalytic carbonylative rearrangement to form fused bicyclic dienones.These vignettes and others described in this Account highlight some of the implications of metal-metal bonding in promoting a challenging step in a catalytic cycle or adjusting the thermodynamic landscape of key intermediates. Given that our studies have focused nearly exclusively on the (NDI)Ni2 system, we anticipate that many more such cases are left to be discovered as other transition-metal combinations and ligand classes are explored.

Constructing an Acidic Microenvironment by MoS2 in Heterogeneous Fenton Reaction for Pollutant Control.

Although Fenton or Fenton-like reactions have been widely used in the environment, biology, life science, and other fields, the sharp decrease in their activity under macroneutral conditions is still a large problem. This study reports a MoS2 cocatalytic heterogeneous Fenton (CoFe2 O4 /MoS2 ) system capable of sustainably degrading organic pollutants, such as phenol, in a macroneutral buffer solution. An acidic microenvironment in the slipping plane of CoFe2 O4 is successfully constructed by chemically bonding with MoS2 . This microenvironment is not affected by the surrounding pH, which ensures the stable circulation of Fe3+ /Fe2+ on the surface of CoFe2 O4 /MoS2 under neutral or even alkaline conditions. Additionally, CoFe2 O4 /MoS2 always exposes "fresh" active sites for the decomposition of H2 O2 and the generation of 1 O2 , effectively inhibiting the production of iron sludge and enhancing the remediation of organic pollutants, even in actual wastewater. This work not only experimentally verifies the existence of an acidic microenvironment on the surface of heterogeneous catalysts for the first time, but also eliminates the pH limitation of the Fenton reaction for pollutant remediation, thereby expanding the applicability of Fenton technology.

Constructing an Acidic Microenvironment by MoS2 in Heterogeneous Fenton Reaction for Pollutant Control

AbstractAlthough Fenton or Fenton‐like reactions have been widely used in the environment, biology, life science, and other fields, the sharp decrease in their activity under macroneutral conditions is still a large problem. This study reports a MoS2 cocatalytic heterogeneous Fenton (CoFe2O4/MoS2) system capable of sustainably degrading organic pollutants, such as phenol, in a macroneutral buffer solution. An acidic microenvironment in the slipping plane of CoFe2O4 is successfully constructed by chemically bonding with MoS2. This microenvironment is not affected by the surrounding pH, which ensures the stable circulation of Fe3+/Fe2+ on the surface of CoFe2O4/MoS2 under neutral or even alkaline conditions. Additionally, CoFe2O4/MoS2 always exposes “fresh” active sites for the decomposition of H2O2 and the generation of 1O2, effectively inhibiting the production of iron sludge and enhancing the remediation of organic pollutants, even in actual wastewater. This work not only experimentally verifies the existence of an acidic microenvironment on the surface of heterogeneous catalysts for the first time, but also eliminates the pH limitation of the Fenton reaction for pollutant remediation, thereby expanding the applicability of Fenton technology.

Mechanisms of water oxidation on heterogeneous catalyst surfaces

Water oxidation, an essential step in photosynthesis, has attracted intense research attention. Understanding the reaction pathways at the electrocatalyst/water interface is of great importance for the development of water oxidation catalysts. How the water is oxidized on the electrocatalyst surface by the positive charges is still an open question. This review summarizes current advances in studies on surface chemistry within the context of water oxidation, including the intermediates, reaction mechanisms, and their influences on the reaction kinetics. The Tafel analyses of some electrocatalysts and the rate-laws relative to charge consumption rates are also presented. Moreover, how the multiple charge transfer relies on the intermediate coverage and the accumulated charge numbers is outlined. Lastly, the intermediates and rate-determining steps on some water oxidation catalysts are discussed based on density functional theories.