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Aluminosilicate (Al‐SiO2) thin films with vertically aligned mesochannels were successfully synthesized on Indium Tin Oxide (ITO) electrodes and employed for the immobilization of a cationic Ru(II) water oxidation catalyst without requiring linker groups. Optimal synthesis conditions yielded uniform mesoporous Al‐SiO2 films with tunable Al content, high surface area (568 m2/g), 3.94 nm pore size, and 155 nm thickness. Electrochemical studies confirmed the presence of the immobilized Ru complex undergoing diffusion‐controlled Ru(III/II) and Ru(IV/III) electron transfer. The Ru loading reached 4.71 nmol/cm2 at Si/Al=9.6, with higher Al content enhancing loading amounts via cation exchange. The Ru‐modified electrode exhibited high electrocatalytic water oxidation activity, achieving 75.3 % Faradaic efficiency and a turnover number of 298.6 for O2 evolution for 1 hour. This work provides a new approach to construct porous environments on an electrode surface to immobilize positively charged transition‐metal complexes as catalysts, offering potential applications in the development of electrocatalytic systems for energy conversion. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have been regarded as promising photocatalytic materials. However, the sluggish diffusion of photoinduced charges in a single‐component COF remains the obstacles that have to be overcome. Here, we demonstrate a synthesis of a COF bearing dual cocatalysts Co3O4 and Re complex as photocatalyst for water oxidation. The dual cocatalysts are coordinated on the COF, and enable the spatial separation of photoinduced charges. The generated electrons were attracted to Re moiety, while the holes were localized on Co3O4 cocatalyst for water oxidation to produce O2 product. The synergy of dual cocatalysts of COF promote the charge separation and redox reaction. Moreover, hydroxyl radicals generated from the hydration of COF contribute to O−O bond formation, which is the key step of O2 formation. Accordingly, an excellent O2 production rate of 400 μmol g−1 h−1 under visible light irradiation was obtained. This work may pave the way to the development of highly efficient COF photocatalysts for solar energy conversion. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting is a viable strategy to produce renewable fuels such as hydrogen. Oxygen evolution reaction (OER) at the anode is getting more attention than hydrogen evolution reaction (HER) because of its higher overpotential and slower electron transfer process. Many advancements in the construction of an effective electrocatalyst have been made recently in an effort to boost OER activity. Additionally, the commercial RuO2 and Pt-derived catalysts are the most fascinating and active electrocatalysts used in the OER and HER kinetics procedure. They show good activity but the massive price and insufficiency are the main obstacles to their widespread usage in the production of hydrogen and oxygen gas. In this case, SnS2_multi walled carbon nanotubes (MWCNTSs) are directly produced on nickel foam (NF) using hydrothermal synthesis. All the catalysts like SnS2, MWCNTSs, and SnS2_MWCNTSs have been developed, and then they are characterized for structural, morphological, compositional, and electrochemical characterization. The fabricated nanocomposite shows OER onset potential of 1.33 V, 116 mV overpotential at 10 mAcm−2, and has a Tafel slope of 47 mVdec−1. In contrast, its HER onset potential is −0.3 V having 209 mV overpotential at 10 mAcm−2 current density and a Tafel slope of 135 mVdec−1. The presence of more electroactive sites, the lowest charge transfer resistance at the electrode-electrolyte interface, the distinct and uniform nanocrystal-like morphology, and the synergistic interaction between SnS2 and MWCNTS are some of the factors that contribute to the low value of overpotential of SnS2_MWCNTSs. The resultant electrocatalyst worked well for the very effective oxidation of water and has a variety of possible applications. Highlights: The SnS2_multi walled carbon nanotube (MWCNT) are directly grown on nickel foam (NF) using hydrothermal method. The SnS2_MWCNT are characterized for structural, morphological, compositional, and electrochemical characterization using various analytical tools. The SnS2_MWCNT shows OER overpotential of 116 mV at 10 mAcm−2 and has a Tafel slope of 47 mVdec−1. The SnS2_MWCNT shows HER overpotential 209 mV at 10 mAcm−2 and a Tafel slope of 135 mVdec−1. [ABSTRACT FROM AUTHOR]

In Photosystem II, light-induced water splitting occurs via the S state cycle of the CaMn4O5-cluster. To understand the role of various possible conformations of the CaMn4O5-cluster in this process, the temperature dependence of the S1 → S2 and S2 → S3 state transitions, induced by saturating laser flashes, was studied in spinach photosystem II membrane preparations under different conditions. The S1 → S2 transition temperature dependence was shown to be much dependent on the type of the cryoprotectant and presence of 3.5% methanol, resulting in the variation of transition half-inhibition temperature by 50 K. No similar effect was observed for the S2 → S3 state transition, for which we also show that both the low spin g = 2.0 multiline and high spin g = 4.1 EPR configurations of the S2 state advance with similar efficiency to the S3 state, both showing a transition half-inhibition temperature of 240 K. This was further confirmed by following the appearance of the Split S3 EPR signal. The results are discussed in relevance to the functional and structural heterogeneity of the water oxidizing complex intermediates in photosystem II. [ABSTRACT FROM AUTHOR]

Calcium and chloride are activators of oxygen evolution in photosystem II (PSII), the light-absorbing water oxidase of higher plants, algae, and cyanobacteria. Calcium is an essential part of the catalytic Mn4CaO5 cluster that carries out water oxidation and chloride has two nearby binding sites, one of which is associated with a major water channel. The co-activation of oxygen evolution by the two ions is examined in higher plant PSII lacking the extrinsic PsbP and PsbQ subunits using a bisubstrate enzyme kinetics approach. Analysis of three different preparations at pH 6.3 indicates that the Michaelis constant, KM, for each ion is less than the dissociation constant, KS, and that the affinity of PSII for Ca2+ is about ten-fold greater than for Cl−, in agreement with previous studies. Results are consistent with a sequential binding model in which either ion can bind first and each promotes the activation by the second ion. At pH 5.5, similar results are found, except with a higher affinity for Cl− and lower affinity for Ca2+. Observation of the slow-decaying Tyr Z radical, YZ•, at 77 K and the coupled S2YZ• radical at 10 K, which are both associated with Ca2+ depletion, shows that Cl− is necessary for their observation. Given the order of electron and proton transfer events, this indicates that chloride is required to reach the S3 state preceding Ca2+ loss and possibly for stabilization of YZ• after it forms. Interdependence through hydrogen bonding is considered in the context of the water environment that intervenes between Cl− at the Cl−1 site and the Ca2+/Tyr Z region. [ABSTRACT FROM AUTHOR]

The green algal genus Picochlorum is of biotechnological interest because of its robust response to multiple environmental stresses. We compared the metabolic performance of P. SE3 and P. oklahomense to diverse microbial phototrophs and observed exceptional performance of photosystem II (PSII) in light energy conversion in both Picochlorum species. The quantum yield (QY) for O2 evolution is the highest of any phototroph yet observed, 32% (20%) by P. SE3 (P. okl) when normalized to total PSII subunit PsbA (D1) protein, and 80% (75%) normalized per active PSII, respectively. Three factors contribute: (1) an efficient water oxidizing complex (WOC) with the fewest photochemical misses of any organism; (2) faster reoxidation of reduced (PQH2)B in P. SE3 than in P. okl. (period-2 Fourier amplitude); and (3) rapid reoxidation of the plastoquinol pool by downstream electron carriers (Cyt b6f/PETC) that regenerates PQ faster in P. SE3. This performance gain is achieved without significant residue changes around the QB site and thus points to a pull mechanism involving faster PQH2 reoxidation by Cyt b6f/PETC that offsets charge recombination. This high flux in P. SE3 may be explained by genomically encoded plastoquinol terminal oxidases 1 and 2, whereas P. oklahomense has neither. Our results suggest two distinct types of PSII centers exist, one specializing in linear electron flow and the other in PSII-cyclic electron flow. Several amino acids within D1 differ from those in the low-light-descended D1 sequences conserved in Viridiplantae, and more closely match those in cyanobacterial high-light D1 isoforms, including changes near tyrosine Yz and a water/proton channel near the WOC. These residue changes may contribute to the exceptional performance of Picochlorum at high-light intensities by increasing the water oxidation efficiency and the electron/proton flux through the PSII acceptors (QAQB). [ABSTRACT FROM AUTHOR]

In oxygen-evolving photosystem II (PSII), the multi-phasic electron transfer from a redox-active tyrosine residue (TyrZ) to a chlorophyll cation radical (P680+) precedes the water-oxidation chemistry of the S-state cycle of the Mn4Ca cluster. Here we investigate these early events, observable within about 10 ns to 10 ms after laser-flash excitation, by time-resolved single-frequency infrared (IR) spectroscopy in the spectral range of 1310–1890 cm−1 for oxygen-evolving PSII membrane particles from spinach. Comparing the IR difference spectra at 80 ns, 500 ns, and 10 µs allowed for the identification of quinone, P680 and TyrZ contributions. A broad electronic absorption band assignable P680+ was used to trace largely specifically the P680+ reduction kinetics. The experimental time resolution was taken into account in least-square fits of P680+ transients with a sum of four exponentials, revealing two nanosecond phases (30–46 ns and 690–1110 ns) and two microsecond phases (4.5–8.3 µs and 42 µs), which mostly exhibit a clear S-state dependence, in agreement with results obtained by other methods. Our investigation paves the road for further insight in the early events associated with TyrZ oxidation and their role in the preparing the PSII donor side for the subsequent water oxidation chemistry. [ABSTRACT FROM AUTHOR]

This paper reviews our historical developments of broken-symmetry (BS) and beyond BS methods that are applicable for theoretical investigations of metalloenzymes such as OEC in PSII. The BS hybrid DFT (HDFT) calculations starting from high-resolution (HR) XRD structure in the most stable S1 state have been performed to elucidate structure and bonding of whole possible intermediates of the CaMn4Ox cluster (1) in the Si (i = 0 ~ 4) states of the Kok cycle. The large-scale HDFT/MM computations starting from HR XRD have been performed to elucidate biomolecular system structures which are crucial for examination of possible water inlet and proton release pathways for water oxidation in OEC of PSII. DLPNO CCSD(T0) computations have been performed for elucidation of scope and reliability of relative energies among the intermediates by HDFT. These computations combined with EXAFS, XRD, XFEL, and EPR experimental results have elucidated the structure, bonding, and reactivity of the key intermediates, which are indispensable for understanding and explanation of the mechanism of water oxidation in OEC of PSII. Interplay between theory and experiments have elucidated important roles of four degrees of freedom, spin, charge, orbital, and nuclear motion for understanding and explanation of the chemical reactivity of 1 embedded in protein matrix, indicating the participations of the Ca(H2O)n ion and tyrosine(Yz)-O radical as a one-electron acceptor for the O–O bond formation. The Ca-assisted Yz-coupled O–O bond formation mechanisms for water oxidation are consistent with recent XES and very recent time-resolved SFX XFEL and FTIR results. [ABSTRACT FROM AUTHOR]

Herein, we report that a copper complex [Cu(dpaq)](ClO4) (1) (H‐dpaq = 2‐[bis(pyridin‐2‐ylmethyl)]amino‐N‐quinolin‐8‐yl‐acetamide) acts as a molecular water oxidation catalyst (WOC) under strong basic condition. Complex 1 oxidizes water to dioxygen in 0.1 M phosphate buffer solution at pH 12.0, exhibiting a turnover frequency of 3.1 × 102 s−1 at a low overpotential (η) of ∼550 mV versus NHE at 1 mA cm−2. A turnover number of 4.0 can be obtained during controlled potential electrolysis (CPE) using 0.25 mM complex 1 at a potential of 1.5 V at pH 12.0 for 3 h. Postelectrolysis analysis, rinse tests, and chelating assays collectively support the homogeneous nature of the electrocatalyst. Mechanistic investigations and quantum chemical calculations reveal a pathway wherein two successive ligand‐centered oxidations transform the catalyst into a Cu(II)(dpaq•)O•. intermediate. Absence of any metal centered oxidation renders the oxidized intermediate less electrophilic, resulting in the survival of the methylene groups present on the ligand backbone against oxidation. The formation of the O─O bond is proposed to proceed via two consecutive single electron transfers (SET) from incoming hydroxide ions to the formal CuIV–oxo species. [ABSTRACT FROM AUTHOR]

Metal‐organic hybrid catalysts with highly tunable single‐sites are promising for oxygen‐evolution reaction (OER), but molecular‐scale understanding of underlying reaction mechanisms still remain elusive on these bulk materials. Herein, we report a direct construction of heterogenized molecular complexes stabilized on carbon substrates via coordinating Fe−Ni sites with four aromatic carboxylate ligands (FeNi‐Lx). The ligands‐tuning π‐π stacking interaction between aromatic carboxylate ligands and carbon supports promote the oxidative charge accumulation on Fe−Ni sites via fast electron transferring, thus the optimized FeNi‐Lx rendering a mass activity of 6680 A gFe/Ni−1 at 0.3 V overpotential. In situ characteristics and theoretical analysis demonstrate that the OH− nucleophilic attack on hypervalent iron sites induce the reconstruction of active Fe−O−Ni species, accompanying with fast valence increasing. Whereas, during OER, the unexpected valence reduction of Fe−O−Ni sites would be attributed to the oxygen‐generating from OOH* intermediates. These findings would establish an essential understanding of the origin of active centers in molecular complexes catalysts for oxygen‐evolution. [ABSTRACT FROM AUTHOR]

In recent years, copper tungsten oxide (CuWO 4) has attracted increasing attention as a highly potential candidate for photoelectrochemical (PEC) water splitting, primarily because of its suitable bandgap, which enables efficient light absorption. However, challenges such as high charge recombination and poor bulk transport have resulted in low PEC performance. To address this, MXene, a novel member of two-dimensional (2D) material, was used to mitigate charge recombination by serving as a hole-transporting layer (HTL) deposited onto a CuWO 4 /FTO substrate. In this study, MXene was fabricated by interactions with different solvents, including tetramethyl ammonium hydroxide (TMAOH), hydrazine (N 2 H 4), and potassium hydroxide (KOH). The work function of MXene and interlayer spacing were adjusted via the intercalation process with various intercalant agents which changes the surface functional groups of MXene to modify the work function and increase the surface area. In addition, the generation of Schottky contact at the CuWO 4 /MXene interface could improve the charge transfer and decrease the charge recombination. The photoelectrodes synthesized in this study were thoroughly characterized using various analytical techniques, including linear sweep voltammetry, high-resolution transmission electron microscopy, electrochemical impedance spectroscopy, and ultraviolet spectroscopy. The results showed a notable improvement in the photoelectrochemical (PEC) performance of 0.35 mA/cm2 of the FTO/CuWO 4 /TMAOH-MXene/Co-Pi photoanode. The synergistic combination of CuWO 4 and MXene facilitated efficient charge transfer from CuWO 4 to the intercalated MXene and reduced electron-hole recombination. The findings suggest that MXene-modified CuWO 4 photoelectrodes hold great potential for efficient hydrogen production, thereby advancing the development of sustainable energy technology. [Display omitted] • The interlayer spacing and work function of MXene were adjusted by the intercalation agents. • The design of CuWO 4 /TMAOH-MXene/Co-Pi photoelectrode exhibited an outstanding PEC performance. • MXene acted as a hole-transporting layer and enhanced the stability of CuWO 4 photoelectrode. [ABSTRACT FROM AUTHOR]

Pyrolytic single Fe atom‐nitrogen‐carbon materials (Fe−N−C) and their derivatives are excellent catalysts for electrochemical oxygen reduction reactions. However, they exhibit poor oxygen evolution reaction (OER) activity due to non‐optimal Fe−O* bonding. This limitation is overcome via electronic structure modulation (i. e., tuning the heteroatom type, concentration, and location within Fe's n≥1 coordination sphere). However, the methods used are complex and energy‐intensive (i. e., 1000 to 1200 °C) raising concerns about reproducibility and cost. This study introduces a method for synthesizing nonpyrolytic Fe−N−C/Fe2O3 composites with similar electronic structure modulation as pyrolytic Fe−N−C and OER activity akin to commercial RuO2. The methodology involves doping low‐melting hydrated Fe‐salts in electrospun polyacrylonitrile nanofiber to catalyze its transformation into conjugated pyridinic‐N‐rich graphite‐like sheets (i. e., N−C) at 300 °C. N−C chelate effectively with oxygen‐vacant (Ov)‐rich Fe atoms derived from Fe2O3 NPs resulting in Fe−N−C/Fe2O3 heterostructures. The Fe2O3 coupling effectively tunes Fe−N−C's electronic structure via Ov modulation. Consequently, the Fermi and d‐orbital energy levels are optimized leading to partial filling of the antibonding states, optimal Fe−O* bonding, high electrochemically active surface area, and OER activity. Because Fe−N−C /Fe2O3 is synthesized at 300 °C using well‐established techniques, its complexity and cost are favorable compared to pyrolytic Fe−N−C materials. [ABSTRACT FROM AUTHOR]

Large‐scale hydrogen production through water splitting represents an optimal approach for storing sustainable but intermittent energy sources. However, water oxidation, a complex and sluggish reaction, poses a significant bottleneck for water splitting efficiency. The impact of outer chemical environments on the reaction kinetics of water oxidation catalytic centers remains unexplored. Herein, chemical environment impacts were integrated by featuring methylpyridinium cation group (Py+) around the classic Ru(bpy)(tpy) (bpy=2,2'‐bipyridine, tpy=2,2′ : 6′,2′′‐terpyridine) water oxidation catalyst on the electrode surface via electrochemical co‐polymerization. The presence of Py+ groups could significantly enhance the turnover frequencies of Ru(bpy)(tpy), surpassing the performance of typical proton acceptors such as pyridine and benzoic acid anchored around the catalyst. Mechanistic investigations reveal that the flexible internal proton acceptor anions induced by Py+ around Ru(bpy)(tpy) are more effective than conventionally anchored proton acceptors, which promoted the rate‐determining proton transfer process and enhanced the rate of water nucleophilic attack during O−O bond formation. This study may provide a novel perspective on achieving efficient water oxidation systems by integrating cations into the outer chemical environments of catalytic centers. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks with unique π architectures and pores could be developed as photocatalysts for transformations. However, they usually form π‐stacking layers, so that only surface layers function in photocatalysis. Here we report a strategy for developing vertically expanded frameworks to expose originally inaccessible active sites hidden in layers to catalysis. We designed covalently linked two‐dimensional cobalt(II) porphyrin layers and explored coordination bonds to connect the cobalt(II) porphyrin layers with bidentate ligands via a three‐component one‐pot polymerization. The resultant frameworks expand the interlayer space greatly, where both the up and down faces of each cobalt(II) porphyrin layer are exposed to reactants. Unexpectedly, the vertically expanded frameworks increase skeleton oxidation potentials, decrease exciton dissociation energy, improve pore hydrophilicity and affinity to water, and facilitate water delivery. Remarkably, these positive effects work collectively in the photocatalysis of water oxidation into oxygen, with an oxygen production rate of 1155 μmol g−1 h−1, a quantum efficiency of 1.24 % at 450 nm, and a turnover frequency of 1.39 h−1, which is even 5.1‐fold as high as that of the π‐stacked frameworks and ranks them the most effective photocatalysts. This strategy offers a new platform for designing layer frameworks to build various catalytic systems for chemical transformations. [ABSTRACT FROM AUTHOR]

Constructing an internal electric field (IEF) within the hematite (Fe2O3) photoanode for highly efficient water oxidation performance with facilitated charge transfer and separation remains still a significant challenge. Unlike the conventional approach of creating interfacial electric fields through heterojunction design by introducing another semiconductor, a novel strategy is proposed for engineering localized n‐p homojunctions on the surface of Fe2O3 photoanode using gradient Zn2+ doping strategy. By implementing this approach, the inherent n‐type characteristics of Fe2O3 can be transformed into p‐type, thereby facilitating the formation of an n‐p junction with robust IEF, which enables more efficient charge separation and transfer. Additionally, the gradient Zn2+ doping is accompanied by the generation of oxygen vacancies, which further improves the charge transfer efficiency and accelerates water oxidation kinetics. As expected, the photocurrent density of optimized Fe2O3 photoanode at 1.23 V versus reversible hydrogen electrode is ≈2.6‐fold that of Fe2O3. This work provides a novel perspective on the design of localized n‐p homojunction within photoanodes for achieving high solar energy conversion efficiency. [ABSTRACT FROM AUTHOR]

Bismuth vanadate (BVO) with a small band gap and suitable band edges is regarded as one of the promising photocatalysts for water oxidation. However, the short charge-transfer path limits its photocatalytic performance. Establishing a heterojunction and incorporating a co-catalyst are feasible methods to improve the photocatalytic ability of BVO by enhancing carrier transfer rates and reducing in-electrode resistances. In this study, nickel tellurium oxide (NTO) and cobalt iron Prussian blue analogues (CoFePBA) are incorporated into the BVO electrode to respectively develop a heterojunction and decorate co-catalyst for efficiently catalyzing the water oxidation reaction for the first time. Different amounts of CoFePBA are deposited on the NTO/BVO electrode by varying the electrodeposition durations to enhance exited charge generations and maintain high absorbance of incident light. The largest photocurrent density of 6.55 mA/cm2 at 1.23 V versus reversible hydrogen electrode is attained for the optimal CoFePBA/NTO/BVO electrode prepared using an electrodeposition duration of 2 min. Excellent catalytic stability is also achieved, with the photocurrent retention of 91.9% after illuminating the electrode for 5000 s. This study provides blueprints for incorporating novel electrochemically active materials in the BVO system to realize heterojunction and co-catalyst strategies, thereby attaining excellent photocatalytic ability toward water oxidation. [Display omitted] • Ni–Te oxide (NTO) and Co–Fe Prussian blue analogue (CoFePBA) combined in BiVO 4 (BVO). • Heterojunction and co-catalyst are made for catalyzing water oxidation efficiently. • Different CoFePBA amount is deposited on NTO/BVO by varying electrodeposition times. • A photocurrent density of 6.55 mA/cm2 at 1.23 V RHE is obtained for CoFePBA/NTO/BVO. • Excellent stability is achieved with a photocurrent retention of 91.9% after 5000 s. [ABSTRACT FROM AUTHOR]

Most electrocatalysts are known to experience structural change during the oxygen evolution reaction (OER) process. Considerable endeavors have been dedicated thus far to comprehending the catalytic process and uncovering the underlying mechanism. During the dynamic evolution of catalyst structure, component leaching of electrocatalysts is the most common phenomenon. This article offers a concise overview of recent findings and developments related to the leaching phenomena in the OER process in terms of fundamental understanding of leaching, advanced characterization techniques used to investigate leaching, leaching of inactive components, and leaching of active components. Leaching behaviors and the induced effects in various kinds of OER catalysts are discussed, progress in manipulating leaching amount/degree toward a tunable surface evolution is spotlighted, and finally, three representative types of structure transformations induced by leaching metastable species in OER condition are proposed. By understanding the process of component leaching in the OER, it will provide more guidance for the rational design of superior electrocatalysts. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) water splitting is regarded as a potential technique for converting solar energy. However, the fast charge recombination and slow water oxidation kinetics significantly have hindered its practical application. It is found that an elevation in operation temperature can activate the charge transport in the photoanodes. Here, a strategy was performed that carbon nanoparticles were employed to TiO2 nanorods, acting as electron reservoirs as well as photothermal materials. More specifically, a record photocurrent density of 1.62 mA cm−2 at 1.23 V vs. RHE has been achieved, accompanied by a high charge separation efficiency of 96% and a long-term durability for 8 h. The detailed experimental results reveal that under NIR light irradiation, the synergistic effect between electron storage and temperature rise leads to accelerated charge transport in the bulk and water oxidation kinetics on the surface. This research offers a new perspective on how to boost the PEC performance of photoelectrodes. [ABSTRACT FROM AUTHOR]

Photosystem II (PSII) is a multi‐subunit protein‐pigment complex with diverse redox‐active cofactors, which enabled the biological availability of O2 on Earth. The substrate specificity and the underlying redox chemistry of the Mn4CaO5 catalytic center are investigated using alternate substrates such as small molecules (ammonia and methanol) and halides (Cl‐, Br‐, I‐) instead of the natural substrate water. Changes in the kinetic profiles of steady‐state O2 evolution and of dichlorophenolindophenol (DCIP) photochemical reduction by PSII as well as the detection of modified sites by proteomic analysis implied the possibility of alternate substrate photooxidation. Of particular interest is the role of two chlorides bound close to the putative water channels in the native system. The mutation of D2‐K317 to alanine is believed to impair the binding of a catalytically relevant chloride, eliminating the chloride requirement for water oxidation catalysis. The efficiency of small molecule photooxidation by the OEC is enhanced by the mutated D2‐K317A PSII complex without the competition from chloride. These results provide insight into the role of bound chloride in native PSII as a filter for enhancing the selectivity of water oxidation. The design principles for PSII may be extended to new strategies for developing highly selective catalysts. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) water splitting is pivotal for addressing the clean and renewable energy demands. However, developing low‐cost, efficient, and robust non‐precious metal catalysts for the acidic oxygen evolution reaction (OER) remains a significant challenge. In this study, we introduced Ce to modulate the electronic structure of Co3O4, enhancing the stability of Co3O4 without compromising its activity. Ce‐doped Co3O4 nanoparticles were electrodeposited onto Ti‐doped hematite surfaces (Ce : Co3O4/Fe2O3), significantly enhancing the PEC performance for water splitting under acidic conditions. These catalysts achieved high photocurrent densities and exhibited prolonged stability. Functioning as p‐type semiconductors, the Ce : Co3O4 nanoparticles not only boosted light absorption but also formed a p‐n heterojunction with the Ti‐doped hematite. This heterojunction generated a built‐in electric field that facilitated the separation and transfer of photogenerated carriers, thereby improving charge separation efficiency. Additionally, these nanoparticles expanded the active surface area of hematite and served as a co‐catalyst, markedly accelerating the OER kinetics. The Ce : Co3O4/Fe2O3 photoanode achieved an impressive photocurrent density of 1.08 mA cm−2 at 1.23 VRHE in acidic media, demonstrating its enhanced activity and stability. [ABSTRACT FROM AUTHOR]

Water oxidation is a crucial reaction in the artificial photosynthesis system. In the present work, density functional calculations were employed to decipher the mechanism of water oxidation catalyzed by a binuclear cobalt complex, which was disclosed to be a homogeneous water oxidation catalyst in pH=7 phosphate buffer. The calculations showed that the catalytic cycle starts from the CoIII,III−OH2 species. Then, a proton‐coupled electron transfer followed by a one‐electron transfer process leads to the generation of the formal CoIV,IV−OH intermediate. The subsequent PCET produces the active species, namely the formal CoIV,V=O intermediate (4). The oxidation processes mainly occur on the ligand moiety, including the coordinated water moiety, implying a redox non‐innocent behavior. Two cobalt centers keep their oxidation states and provide one catalytic center for water activation during the oxidation process. 4 triggers the O−O bond formation via the water nucleophilic attack pathway, in which the phosphate buffer ion functions as the proton acceptor. The O−O bond formation is the rate‐limiting step with a calculated total barrier of 17.7 kcal/mol. The last electron oxidation process coupled with an intramolecular electron transfer results in the generation of O2. [ABSTRACT FROM AUTHOR]

This report describes a systematic approach for precise engineering of a catalyst‐metal oxide interface through combining complementary approaches of chemical vapor deposition and atomic layer deposition. Specifically, Chemical Vapor Deposition (CVD) fabricated nanostructured hard‐carbon framework (NCF) is employed as synergistic support for precise deposition of NiOx particles through Atomic Layer Deposition (ALD). The three variants of NCF‐NiOx system (dimensions ranging from 3–12 nm, surface coverage ranging from 0.14 %–2 %) achieved exhibit unique electrocatalytic water oxidation activities, that are further strongly influenced by an external magnetic field (Hext). This confluence of size engineering and associated magnetic field effects interplay to produce the largest lowering in Rct at Hext=200 mT. A comprehensive analysis of electrocatalytic parameters including the Tafel slope and double layer capacitance establishes further insights on co‐relation of size effect and magnetic properties to understand the role of nanocarbon supported transition metal oxides in water electrolysis. [ABSTRACT FROM AUTHOR]

Photosystem II (PSII) uses light energy to oxidize water and to reduce plastoquinone in the photosynthetic electron transport chain. O2 is produced as a byproduct. While most members of the PSII research community agree that O2 originates from water molecules, alternative hypotheses involving bicarbonate persist in the literature. In this perspective, we provide an overview of the important roles of bicarbonate in regulating PSII activity and assembly. Further, we emphasize that biochemistry, spectroscopy, and structural biology experiments have all failed to detect bicarbonate near the active site of O2 evolution. While thermodynamic arguments for oxygen-centered bicarbonate oxidation are valid, the claim that bicarbonate is a substrate for photosynthetic O2 evolution is challenged. [ABSTRACT FROM AUTHOR]

One of the reasons for the high efficiency and selectivity of biological catalysts arise from their ability to control the pathways of substrates and products using protein channels, and by modulating the transport in the channels using the interaction with the protein residues and the water/hydrogen-bonding network. This process is clearly demonstrated in Photosystem II (PS II), where its light-driven water oxidation reaction catalyzed by the Mn4CaO5 cluster occurs deep inside the protein complex and thus requires the transport of two water molecules to and four protons from the metal center to the bulk water. Based on the recent advances in structural studies of PS II from X-ray crystallography and cryo-electron microscopy, in this review we compare the channels that have been proposed to facilitate this mass transport in cyanobacteria, red and green algae, diatoms, and higher plants. The three major channels (O1, O4, and Cl1 channels) are present in all species investigated; however, some differences exist in the reported structures that arise from the different composition and arrangement of membrane extrinsic subunits between the species. Among the three channels, the Cl1 channel, including the proton gate, is the most conserved among all photosynthetic species. We also found at least one branch for the O1 channel in all organisms, extending all the way from Ca/O1 via the 'water wheel' to the lumen. However, the extending path after the water wheel varies between most species. The O4 channel is, like the Cl1 channel, highly conserved among all species while having different orientations at the end of the path near the bulk. The comparison suggests that the previously proposed functionality of the channels in T. vestitus (Ibrahim et al., Proc Natl Acad Sci USA 117:12624-12635, 2020; Hussein et al., Nat Commun 12:6531, 2021) is conserved through the species, i.e. the O1-like channel is used for substrate water intake, and the tighter Cl1 and O4 channels for proton release. The comparison does not eliminate the potential role of O4 channel as a water intake channel. However, the highly ordered hydrogen-bonded water wire connected to the Mn4CaO5 cluster via the O4 may strongly suggest that it functions in proton release, especially during the S0 → S1 transition (Saito et al., Nat Commun 6:8488, 2015; Kern et al., Nature 563:421-425, 2018; Ibrahim et al., Proc Natl Acad Sci USA 117:12624-12635, 2020; Sakashita et al., Phys Chem Chem Phys 22:15831-15841, 2020; Hussein et al., Nat Commun 12:6531, 2021).

Bismuth vanadate (BVO) ranks among the most promising photoanodes for photoelectrochemical (PEC) water splitting. Nonetheless, slow charge separation and transport, besides the sluggish water oxidation kinetics, are key barriers to its photoefficiency. Here, we present a co‐doping strategy that significantly improves the charge separation performance of BVO photoanodes. We found that, under standard one sun illumination, the Fe−N co‐doped BVO photoanode (Fe−N−BVO) by N‐coordinated Fe precursor reaches a record photocurrent density of 7.01 mA cm−2 at 1.23 V vs RHE after modified a surface co‐catalyst (FeNiOOH), and exhibits an outstanding stability. By contrast, much lower photocurrent density is obtained for the N‐doped, Fe‐doped and Fe/N‐doped BVO photoanode with separated N and Fe precursors. The detailed experimental characterizations show that the high activity of the Fe−N co‐doped BVO photoanode is attributed to the enhanced photo‐induced bulk charge separation, as well as the accelerated surface water oxidation kinetics. XPS, EXAFS and DFT calculations clearly show that, instead of formation of deep trapping state in the individually doped BVO, the co‐doping of Fe−N into BVO generates Fe‐based electronic states just below the bottom of conduction band and N‐derived states just above the top of valence band. Such modulations in electronic structure enable the efficient trap of the electrons and holes to enhance the separation of photo‐induced carriers, but hinder the charge recombination originated from the deep trapping sites. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H2O2) is a crucial chemical applied in various industry sectors. However, the current industrial anthraquinone process for H2O2 synthesis is carbon‐intensive. With sunlight and renewable electricity as energy inputs, photocatalysis and electrocatalysis have great potential for green H2O2 production from oxygen (O2) and water (H2O). Herein, we review the advances in pairing two‐electron O2 reduction and two‐electron H2O oxidation reactions for dual‐pathway H2O2 synthesis. The basic principles, paired redox reactions, and catalytic device configurations are introduced initially. Aligning with the energy input, the latest photocatalysts, electrocatalysts, and photo‐electrocatalysts for dual‐pathway H2O2 production are discussed afterward. Finally, we outlook the research opportunities in the future. This minireview aims to provide insights and guidelines for the broad community who are interested in catalyst design and innovative technology for on‐site H2O2 synthesis. [ABSTRACT FROM AUTHOR]

Achieving robust long‐term durability with high catalytic activity at low iridium loading remains one of great challenges for proton exchange membrane water electrolyzer (PEMWE). Herein, we report the low‐temperature synthesis of iridium oxide foam platelets comprising edge‐sharing IrO6 octahedral honeycomb framework, and demonstrate the structural advantages of this material for multilevel tuning of anodic catalyst layer across atomic‐to‐microscopic scales for PEMWE. The integration of IrO6 octahedral honeycomb framework, foam‐like texture and platelet morphology into a single material system assures the generation and exposure of highly active and stable iridium catalytic sites for the oxygen evolution reaction (OER), while facilitating the reduction of both mass transport loss and electronic resistance of catalyst layer. As a proof of concept, the membrane electrode assembly in single‐cell PEMWE based on honeycomb‐structured IrOx foam platelets, with a low iridium loading (~0.3 mgIr/cm2), is demonstrated to exhibit high catalytic activity at ampere‐level current densities and to remain stable for more than 2000 hours. [ABSTRACT FROM AUTHOR]

Water oxidation catalysts (WOCs) with excellent activity and stability are highly desired. Numerous efforts have been dedicated to develop WOCs mimicking the cubic structure and activity of Mn 4 CaO 5 cluster in oxygen-evolving center (OEC) of photosynthesis system II (PSII). Herein, a octanuclear Cu cluster [Cu 8 (dpy{OH}O) 8 (OAc) 4 ]4+ (1 , dpy{OH}O− = the monoanion of the hydrated, gem -diol form of di-2-pyridyl ketone) that contains two Cu 4 O 4 cubic fragments with bioinspired structure mimicking the Mn 4 CaO 5 cluster of OEC of natural PSII is developed as efficient homogeneous catalyst for electrochemical water oxidation under near neutral condition for the first time. It exhibits outstanding water oxidation catalytic activity via accelerating oxygen evolution with onset overpotential of 730 mV and appreciable turnover frequency of 20.1 s−1. Collective experiments together confirmed the homogeneity and stability of cluster 1 under long-term water oxidation catalytic cycle. Kinetic study reveals the water nucleophilic attack (WNA) catalytic mechanism occurs on the coordination unsaturated Cu center of the cluster. This work provides the inspiration of the development of robust bioinspired catalyst for electrochemical water oxidation. A bioinspired octanuclear copper cubane complex is developed as an efficient electrochemical water oxidation catalyst under near neutral condition. Remarkable turnover frequency of 20.1 s−1 is achieved for water oxidation, which is found to be accelerated by the preorganized of water molecular around Cu center by hydrogen bond. [Display omitted] • A copper cluster with bioinspired structure was developed as efficient water oxidation catalyst. • Electrocatalytic water oxidation occurs with high turnover frequency of 20.1 s−1. • This cluster exhibits good stability over 12 h of electrolysis and Faradic efficiency of 93 % is achieved. • Catalysis mechanism involving preorganization of substrate water molecule by hydrogen bond and PCET process was proposed. [ABSTRACT FROM AUTHOR]

α-Fe 2 O 3 attracted great attention as a promising photoanode candidate for photoelectrochemical (PEC) H 2 O spitting. In this paper, one dimensional (1D) α-Fe 2 O 3 nanorods coupled 2D porous In 2 O 3 nanosheet assemblies were designed to construct a S-scheme α-Fe 2 O 3 /In 2 O 3 heterojunction photoanode. The unique porous In 2 O 3 nanosheet assemblies are conductive to improve light-harvesting efficiency and provide more active sites. An internal electric field induced at the α-Fe 2 O 3 /In 2 O 3 heterojunction interface could promote interfacial charge separation and transfer, enhancing redox kinetics. The as-obtained 2D/1D In 2 O 3 /α-Fe 2 O 3 photoanode achieved a stable photocurrent density of 2.2 mA cm−2 at 1.23 V (vs. RHE). It is 6.3 times higher than that of the α-Fe 2 O 3 component, and got a max applied bias photo-to-current efficiency (ABPE) of 0.28%, which is about 5.8 times that of bare α-Fe 2 O 3 at 1.01 V. The work provides a promising strategy to construct high-performance S-scheme heterostructure photoanodes, featuring the role of surface and interface science in sustainable energy. [Display omitted] • 1D α-Fe 2 O 3 nanorods coupled 3D porous In 2 O 3 nanosheet assemblies were constructed. • In 2 O 3 nanosheets modified on α-Fe 2 O 3 nanorods could promote interfacial charge separation and transfer. • α-Fe 2 O 3 /In 2 O 3 photoanode achieved 2.2 mA cm−2 at 1.23 V (vs. RHE) and ABPE of 0.28% at 1.01 V. • The photoanode follows a S-scheme mechanism for enhanced photoelectrochemical activity. [ABSTRACT FROM AUTHOR]

Recently, tungsten oxide (WO 3) and bismuth vanadate (BiVO 4) have been considered as an intriguing combination for constructing a heterojunction for efficient photoelectrochemical (PEC) applications. Herein, we report the preparation of ternary WO 3 /BiVO 4 /NiCo layered double hydroxide (LDH) photoanodes for boosting photogenerated carrier transport and promotion of catalytic activity. WO 3 /BiVO 4 heterostructures were synthesized by a hydrothermal process of WO 3 nanoplates on a fluorine-doped tin oxide (FTO) glass substrate, followed by spin-coating for BiVO 4 materials. We investigated the effect of a NiCo LDH catalyst on PEC performance by controlling the growth temperatures of the NiCo LDH via hydrothermal synthesis. Moreover, the X-ray diffraction (XRD), Fourier‒transform infrared (FTIR) and X‒ray photoelectron spectroscopy (XPS) analyses revealed that the WO 3 /BiVO 4 heterojunction was retained after the NiCo LDH growth process regardless of synthesis temperatures. The PEC results verified that the WO 3 /BiVO 4 heterostructure with the optimized NiCo LDH catalyst (WBN60) possessed the best photocurrent density of 3.2 mA/cm2 at 1.23 V vs. reversible hydrogen electrode (RHE), which created improved charge separation and surface oxidation kinetics of photogenerated carriers. Consequentially, the smallest charge transfer resistance and recombination rate were achieved in the WBN60 electrode compared to others, indicating a much lower photoelectrode‒electrolyte interfacial resistance and the enhancement of photogenerated carrier transport by suppressing recombination. [ABSTRACT FROM AUTHOR]

Monitoring the dynamic behavior of active species and modulating their electronic architecture are crucial for the development of efficient catalysts. Here, a 3D ordered multi‐level porous Ni2P/CeO2 heterojunction catalyst with a “self‐optimization effect” is strategically synthesized for efficient oxygen evolution reaction (OER). This catalyst exhibits a low overpotential of 235 mV at 20 mA cm−2 in 1.0 m KOH. During the OER process, the heterojunction catalyst specifically undergoes a unique phase transition involving the leaching of the P element, which triggers the formation of the PO43−‐NiOOH/CeO2 catalyst with PO43− adsorbed on the surface of the reconstructed product NiOOH/CeO2. Density functional theory calculations reveal that the CeO2 and adsorbed‐PO43− in the self‐optimized structure are essential and minor factors for enhancing catalytic activity, respectively. They collaborate to promote the redistribution of electron density in surface Ni and O, increasing the d/p‐band center difference. This phenomenon results in optimized adsorption/desorption of the key intermediates such as *OOH and improved catalytic performance. Overall, this research highlights the potential of d/p‐band modulation for the rational design of cost‐effective and high‐efficiency electrocatalysts. [ABSTRACT FROM AUTHOR]

Ultrasound radiation has been widely used in biomedical application for both diagnosis and therapy. Metal oxides nanoparticles (NPs), like ZnO or TiO2 NPs, have been widely demonstrated to act as excellent sonocatalysts and significantly enhance cavitation at their surface, making them optimal for sonodynamic cancer therapy. These NPs often possess semiconductive and piezoelectric properties that contribute to the complex phenomena occurring at the water-oxide interface during sonostimulation. Despite the great potential in applied sonocatalysis and water splitting, the complex mechanism that governs the phenomenon is still a research subject. This work investigates the role of piezoelectric ZnO micro- and nano-particles in ultrasound-assisted water oxidation. Three metal oxides presenting fundamental electronic and mechanical differences are evaluated in terms of ultrasound-triggered reactive oxygen species generation in aqueous media: electromechanically inert SiO2 NPs, semiconducting TiO2 NPs, piezoelectric and semiconducting ZnO micro- and nanoparticles with different surface areas and sizes. The presence of silver ions in the aqueous solution was further considered to impart a potential electron scavenging effects and better evaluate the oxygen generation performances of the different structures. Following sonoirradiation, the particles are optically and chemically analyzed to study the effect of sonostimulation at their surface. The production of gaseous molecular oxygen is measured, revealing the potential of piezoelectric particles to generate oxygen under hypoxic conditions typical of some cancer environments. Finally, the best candidates, i.e. ZnO nano and micro particles, were tested on osteosarcoma and glioblastoma cell lines to demonstrate their potential for cancer treatment. [ABSTRACT FROM AUTHOR]

Stable homogeneous two‐electron water oxidation electrocatalysts are highly demanded to understand the precise mechanism and reaction intermediates of electrochemical H2O2 production. Here we report a tetranuclear manganese complex with a cubane structure which can electrocatalyze water oxidation to hydrogen peroxide under alkaline and neutral conditions. Such a complex demonstrates an optimal Faradaic efficiency (FE) of 87 %, which is amongst (if not) the highest FE(H2O2) of reported homogeneous and heterogeneous electrocatalysts. In addition, active species were identified and co‐catalysts were excluded through ESI‐MS characterization. Furthermore, we identified water binding sites and isolated one‐electron oxidation intermediate by chemical oxidation of the catalyst in the presence of water substrates. It is evident that efficient proton‐accepting electrolytes avoid rapid proton building‐up at electrode and substantially improve reaction rate and selectivity. Accordingly, we propose a two‐electron catalytic cycle model for water oxidation to hydrogen peroxide with the bioinspired molecular electrocatalyst. The present work is expected to provide an ideal platform to elucidate the two‐electron WOR mechanism at the atomic level. [ABSTRACT FROM AUTHOR]

Four ruthenium water oxidation catalysts that bear carboxylate and sulfonate groups in the active site have been synthesized and analyzed for their catalytic activity. The sulfonate‐containing catalysts show higher electrochemical activity in pH 7 phosphate buffer with 4 times larger catalytic current, improved durability with sacrificial oxidant, and increased solubility compared to similar species containing two carboxylate groups. Density functional theory calculations suggest that the sulfonate group provides a more favorable geometry for water nucleophilic attack, which is both the energetically most favorable mechanism calculated and the experimentally predicted mechanism under electrochemical conditions. Further experimental studies have been performed to show that under certain conditions catalysts can perform well electrochemically under pH conditions as low as 1.6 and that various structural components can greatly change solubility and catalytic operation. [ABSTRACT FROM AUTHOR]

Artificial photosynthesis of H2O2 from H2O and O2 by visible light is a promising approach, but the efficiency is still unsatisfactory because of the inefficient O2 adsorption and proton supply. Here, terphenyl functionalized covalent triazine polymer (CTP‐TD) is prepared for efficient H2O2 production. Experimental and theoretical results show that terphenyl structure can promote O2 adsorption by regulating the oxygen evolution (O2→1O2) and improve proton supply by accelerating water oxidation. The terphenyl structure significantly promotes the singlet oxygen (1O2) production via the intersystem crossing (ISC) process. The electrophilic 1O2 is more easily adsorbed on the catalyst surface than O2. Simultaneously, the accumulated holes at the terphenyl structure lower water oxidation energy barriers and accelerate the water dehydrogenation process. This work provides a valuable reference and new inspiration for the polymer design of efficient H2O2 generation from the perspective of reactant supply. [ABSTRACT FROM AUTHOR]

In this research, the heterogeneous catalysts of Fe3O4@SiO@TiO‐FePc and Fe3O4@SiO@TiO‐ CuPcN (FePc = iron (II) phthalocyanine and CuPcN = copper (II) tetraazaphthalocyanine), termed respectively as nanocomposites 1 and 2, were prepared by immobilizing the FePc and CuPcN complexes on the Fe3O4@SiO@TiO surface and used for the photocatalytic water oxidation reaction. Since phthalocyanine complexes have received very little attention as photocatalysts for water oxidation, the advantage of the synthesized photocatalyst owes to the ability of the phthalocyanine complex grafted on the titanium substrate to oxidize water in the photocatalytic reaction. The prepared nanocomposites were then studied by diffraction (XRD), scanning electron microscopy (SEM), energy‐dispersive X‐ray (EDX), Fourier transform infrared (FT‐IR) spectroscopies, thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), inductively coupled plasma‐optical emission spectroscopy (ICP‐OES), Brunauer–Emmett–Teller (BET) analysis, ultraviolet diffuse reflectance (DRS), and photoluminescence (PL) spectroscopies. The photocatalytic response of water oxidation by nanocomposites 1 and 2 was investigated in the presence of silver nitrate as an electron recipient at ambient temperature. The progress of the water oxidation reaction was monitored with an oxygen meter. The amount of oxygen generated in the presence of nanocomposites 1 and 2 under visible light irradiation was found to be 2.6 and 2.1 mg L−1, respectively. Owing to the existence of magnetic material, these nanocomposites can be effortlessly removed from the response medium with an external magnet. The involved nanocomposites can be used up to three times in catalytic water oxidation reactions with no significant change in their photocatalytic activity. [ABSTRACT FROM AUTHOR]

Water electrolysis is one promising and eco‐friendly technique for energy storage, yet its overall efficiency is hindered by the sluggish kinetics of oxygen evolution reaction (OER). Therefore, developing strategies to boost OER catalyst performance is crucial. With the advances in characterization techniques, an extensive phenomenon of surface structure evolution into an active amorphous layer was uncovered. Surface reconstruction in a controlled fashion was then proposed as an emerging strategy to elevate water oxidation efficiency. In this work, Cr substitution induces the reconstruction of NiFexCr2‐xO4 during cyclic voltammetry (CV) conditioning by Cr leaching, which leads to a superior OER performance. The best‐performed NiFe0.25Cr1.75O4 shows a ~1500 % current density promotion at overpotential η=300 mV, which outperforms many advanced NiFe‐based OER catalysts. It is also found that their OER activities are mainly determined by Ni : Fe ratio rather than considering the contribution of Cr. Meanwhile, the turnover frequency (TOF) values based on redox peak and total mass were obtained and analysed, and their possible limitations in the case of NiFexCr2‐xO4 are discussed. Additionally, the high activity and durability were further verified in a membrane electrode assembly (MEA) cell, highlighting its potential for practical large‐scale and sustainable hydrogen gas generation. [ABSTRACT FROM AUTHOR]

In electrocatalytic applications, catalyst interface crucially influences electrochemical activity and selectivity, balancing adsorption, desorption, and transport of intermediates and electrons. Capitalizing on this fact, this study unveils a novel approach to enhance CoO x surfaces, a promising electrocatalyst for water oxidation, through organic shell functionalization via electrodeposition. Utilizing a dinuclear cobalt complex 1 , resembling CoO x 's structure, we crafted a modified film exhibiting remarkable stability. This film consistently delivered a current density of 2.0 mA/cm2 for oxygen evolution at 1.5 V vs. NHE, sustaining over 25 h under neutral conditions with only a minimal 5% activity reduction. Conversely, the standard CoPi catalyst underwent rapid deterioration, losing about 40% of its initial catalytic current in just 14 h. Further investigations revealed that the organic shell effectively reduces catalyst dissolution, in contrast to the severe dissolution of CoPi, directly impacting its catalytic activity. This approach offers a straightforward means to functionalize various nanostructured materials, potentially enhancing their electrochemical activities and stabilities. [Display omitted] • Interface engineering of electrocatalysts with an organic ligand shell. • Mod-CoPi was electrodeposited from a dinuclear cobalt complex with a polyhydroxy ligand. • The mod-CoPi shows remarkable stability, maintaining over 90% activity for 50 h. • The unmodified CoPi degrades, losing 40% catalytic current in 14 h. • Analyses reveal CoPi dissolution key factor to its activity degradation. [ABSTRACT FROM AUTHOR]

Protein structure plays an essential role on their stability, functionality, and catalytic activity. In this work, the interplay between the β‐sheet structure and its catalytic implications to the design of enzyme‐inspired materials is investigated. Here, inspiration is drawn from the active sites and β‐sheet rich structure of the highly efficient multicopper oxidase (MCO) to engineer a bio‐inspired electrocatalyst for water oxidation utilizing the abundant metal, copper. Copper ions are coordinated to poly‐histidine (polyCuHis), as they are in MCO active sites. The resultant polyCuHis material effectively promotes water oxidation with low overpotentials (0.15 V) in alkaline systems. This activity is due to the 3D structure of the poly‐histidine backbone. By increasing the prevalence of β‐sheet structure and decreasing the random coil nature of the polyCuHis secondary structures, this study is able to modulates the electrocatalytic activity of this material is modulated, shifting it toward water oxidation. These results highlight the crucial role of the local environment at catalytic sites for efficient, energy‐relevant transformations. Moreover, this work highlights the importance of conformational structure in the design of scaffolds for high‐performance electrocatalysts. [ABSTRACT FROM AUTHOR]

Poly(3‐hexylthiophene) (P3HT) film was applied as a photoanode on an electron‐extracting layer‐coated upon a current‐collecting plastic substrate. The film soaked in an aqueous solution (pH 12) exhibited an enhanced anodic current with light illumination, and the photocurrent density (J) reached almost 100 μA/cm2 for its wound cylinder, which was accompanied by oxygen bubble evolution. The light ON/OFF response, light‐intensity proportion, and wavelength‐dependency of the J value supported the photo‐electrolytic function of the P3HT film. The hole‐injection efficiency of the film estimated for water oxidation using a solution involving a sacrificial reagent, was relatively high in the range of 46%–86%. Although an apparent activation energy of 39 kJ/mol for the electrolytic water oxidation in the dark suggested a chemical but catalytic pathway for the film anode, the temperature independence of the photocurrent indicated direct hole‐injection into water or hydroxide ions. The photoanode performance of the P3HT film for water oxidation was discussed in relation to the energy diagram including the highest occupied molecular orbital level. [ABSTRACT FROM AUTHOR]

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X-ray crystallography and X-ray spectroscopy using X-ray free electron lasers plays an important role in understanding the interplay of structural changes in the protein and the chemical changes at the metal active site of metalloenzymes through their catalytic cycles. As a part of such an effort, we report here our recent development of methods for X-ray absorption spectroscopy (XAS) at XFELs to study dilute biological samples, available in limited volumes. Our prime target is Photosystem II (PS II), a multi subunit membrane protein complex, that catalyzes the light-driven water oxidation reaction at the Mn4CaO5 cluster. This is an ideal system to investigate how to control multi-electron/proton chemistry, using the flexibility of metal redox states, in coordination with the protein and the water network. We describe the method that we have developed to collect XAS data using PS II samples with a Mn concentration of

Abstract Most electrocatalysts are known to experience structural change during the oxygen evolution reaction (OER) process. Considerable endeavors have been dedicated thus far to comprehending the catalytic process and uncovering the underlying mechanism. During the dynamic evolution of catalyst structure, component leaching of electrocatalysts is the most common phenomenon. This article offers a concise overview of recent findings and developments related to the leaching phenomena in the OER process in terms of fundamental understanding of leaching, advanced characterization techniques used to investigate leaching, leaching of inactive components, and leaching of active components. Leaching behaviors and the induced effects in various kinds of OER catalysts are discussed, progress in manipulating leaching amount/degree toward a tunable surface evolution is spotlighted, and finally, three representative types of structure transformations induced by leaching metastable species in OER condition are proposed. By understanding the process of component leaching in the OER, it will provide more guidance for the rational design of superior electrocatalysts.

The oxygen evolution reaction (OER) is a vital half-reaction in many applications, such as the electrochemical H2O splitting, CO2, and N2 conversion processes. The OER involves a four-electron transfer and is a kinetically sluggish reaction that requires additional potential to drive. To enhance the electrochemical performance of the above-mentioned applications, highly efficient, corrosion-resistant, earth-abundant, and eco-friendly electrocatalysts are required. Here, we report a highly porous, minimally Ru-doped copper phosphate electrocatalyst obtained through co-precipitation. The optimized electrocatalyst (5% Ru-doped copper phosphate) exhibits a low overpotential of 340 mV to achieve 10 mA cm−2 compared to copper-based materials, and it remains stable over 20 h. The high performance is attributed to a high electrochemically effective surface area (ECSA) of 30.25 cm2, facilitating effective ion transportation at the electrode/electrolyte interface and excellent electrical conductivity. This result is supported by density functional theory calculations, which demonstrate that ruthenium enhances the electrochemical properties by increasing electronic conductivity, reducing the theoretical overpotential, and influencing the rate-determining step of the oxygen evolution reaction. Herein, the electrocatalyst is attractive for commercialization due to its utilization of minimal ruthenium in earth-abundant electrocatalysts, which offer competitive performance.