Aqueous Zn batteries with ideal energy density and absolute safety are deemed the most promising candidates for next-generation energy storage systems. Nevertheless, stubborn dendrite formation and notorious parasitic reactions on the Zn metal anode have significantly compromised the Coulombic efficiency (CE) and cycling stability, severely impeding the Zn metal batteries from being deployed in the proposed applications. Herein, instead of random growth of Zn dendrites, a guided preferential growth of planar Zn layers is accomplished via atomic-scale matching of the surface lattice between the hexagonal close-packed (hcp) Zn(002) and face-centered cubic (fcc) Cu(100) crystal planes, as well as underpotential deposition (UPD)-enabled zincophilicity. The underlying mechanism of uniform Zn plating/stripping on the Cu(100) surface is demonstrated by ab initio molecular dynamics simulations and density functional theory calculations. The results show that each Zn atom layer is driven to grow along the exposed closest packed plane (002) in hcp Zn metal with a low lattice mismatch with Cu(100), leading to compact and planar Zn deposition. In situ optical visualization inspection is adopted to monitor the dynamic morphology evolution of such planar Zn layers. With this surface texture, the Zn anode exhibits exceptional reversibility with an ultrahigh Coulombic efficiency (CE) of 99.9%. The MnO2//Zn@Cu­(100) full battery delivers long cycling stability over 548 cycles and outstanding specific energy and power density (112.5 Wh kg–1 even at 9897.1 W kg–1). This work is expected to address the issues associated with Zn metal anodes and promote the development of high-energy rechargeable Zn metal batteries.

Sulfite oxidases are metalloenzymes that oxidize sulfite to sulfate at a molybdenum active site. In vertebrate sulfite oxidases, the electrons generated at the Mo center are transferred to an external electron acceptor via a heme domain, which can adopt two conformations: a "closed" conformation, suitable for internal electron transfer, and an "open" conformation suitable for intermolecular electron transfer. This conformational change is an integral part of the catalytic cycle. Sulfite oxidases have been wired to electrode surfaces, but their immobilization leads to a significant decrease in their catalytic activity, raising the question of the occurrence of the conformational change when the enzyme is on an electrode. We recorded and quantitatively modeled for the first time the transient response of the catalytic cycle of human sulfite oxidase immobilized on an electrode. We show that conformational changes still occur on the electrode, but at a lower rate than in solution, which is the reason for the decrease in activity of sulfite oxidases upon immobilization.

The bioelectrocatalytic sulfite oxidation by human sulfite oxidase (hSO) on indium tin oxide (ITO) is reported, which is facilitated by functionalizing of the electrode surface with polyethylenimine (PEI)-entrapped CdS nanoparticles and enzyme. hSO was assembled onto the electrode with a high surface loading of electroactive enzyme. In the presence of sulfite but without additional mediators, a high bioelectrocatalytic current was generated. Reference experiments with only PEI showed direct electron transfer and catalytic activity of hSO, but these were less pronounced. The application of the polyelectrolyte-entrapped quantum dots (QDs) on ITO electrodes provides a compatible surface for enzyme binding with promotion of electron transfer. Variations of the buffer solution conditions, e.g., ionic strength, pH, viscosity, and the effect of oxygen, were studied in order to understand intramolecular and heterogeneous electron transfer from hSO to the electrode. The results are consistent with a model derived for the enzyme by using flash photolysis in solution and spectroelectrochemistry and molecular dynamic simulations of hSO on monolayer-modified gold electrodes. Moreover, for the first time a photoelectrochemical electrode involving immobilized hSO is demonstrated where photoexcitation of the CdS/hSO-modified electrode lead to an enhanced generation of bioelectrocatalytic currents upon sulfite addition. Oxidation starts already at the redox potential of the electron transfer domain of hSO and is greatly increased by application of a small overpotential to the CdS/hSO-modified ITO.

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1Introduction Molybdenum (Mo) containing enzymes have been associated with the catalysis of important reactions in the metabolism of smallm oleculess uch as carbon nitrogen, and sulfur [1a, b].T he sulfite oxidizing enzymes sulfite oxidase (SO) and sulfite dehydrogenase (SDH) catalyze the oxidation of sulfite to sulfate accompaniedw ith the release of two electrons and two protons according to the following equation:All sulfite oxidizing enzymes share the same catalytic Mo cofactor (Moco) containingu nit. But the number and type of additional redoxc enters differb etween enzymes from different classes of organisms, which has an impact on the type of electrona cceptor the enzyme can use [2a, b].O nly in the vertebrate SO ah eme b binding domaini sc ovalently linkedt ot he core structure of the enzyme.T he human sulfite oxidase (hSO) shows al arge structural homology to the enzyme from chicken liver (cSO) which is ad imeric enzyme where each subunit of the homodimer consists of an N-terminal heme b binding domain( SO-HD), followed by ap olypeptide tetherc onnectingt he heme domain to the Moco-containing domain (SO-MD) and ad imerization domain at the C-terminus [3].Thes ingle steps of the SO catalyzed reaction involve the two-electron oxidationo fs ulfite to sulfate at the Moco center, where Mo VI is reduced to Mo IV .I nv ertebrate SO the Mo VI regeneration is naturally coupled to the reduction of two equivalents of soluble cytochrome c which proceeds in two subsequent intra-and intermolecular singlee lectron transfer steps via the heme b5 containing site [4a, b, c].T hese steps involve ar epositioning of the domains to reduce electron transfer distances permitting electron transfer from Mo to Fe of SO-HD and to cytochrome c [5a, b].Areaction with soluble [6a, b] and polymerb ound redoxm ediators is also possible [7a, b]. Direct unmediated electron transfer from the reduced enzyme to electrodes proceedsv ia the hemed omain [8]. This process was most effective when the enzymei si mmobilized on electrode surfaces modified with positive charged SAMs facilitating the oriented assembly of SO electron transfer and bioelectrocatalysis [9a, b].Abstract:W er eport efficient bioelectrocatalytic sulfite oxidation by human sulfite oxidase (hSO) immobilizedo n ag old nanoparticle (AuNP)m odified gold electrode.T he AuNP were synthesized in aqueous phase by using branched polyethyleneimine (PEI) as reducing as well as stabilizing agent. Golde lectrodes were modified by as elf assembled monolayer of dithio-bis(N-hydroxysuccinimidyl propionate) (DTSP) onto which the NP and hSO were immobilized. Cyclic voltammetry of the hSO modified electrode in the absence of substrater evealedaquasi-reversible direct electrochemical reactiono ft he heme domaino fhSO with fast electron transfer rate.T he electron transferr ate constant of k s = 32 s À1 and the formal potential E 0 ' = À0.155 Vv s. Ag/AgCl/1 MK Cl were estimated. Comparatives tudies with nanoparticles of BaSO 4 indicate the importance of the NP conductivity for charge transfer an...

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ultimately increasing the charge transfer resistance. [8] During the OER process, the insulated Li 2 O 2 can only be decomposed at high overpotential, which can trigger severe parasitic reactions. [9][10][11] Therefore, exploring efficient bifunctional electrocatalysts and understanding the formation and decomposition mechanism of Li 2 O 2 is of great significance for effectively reducing ORR and OER overpotential and improving the electrochemical performance of LOBs.Currently, two types of mechanisms (solution-mediated pathway and surface adsorption pathway) were commonly recommended to explain the deposition process of Li 2 O 2 on the electrode surface during ORR. Different mechanisms lead to various structure (crystallinity or defect) and morphology (toroid or thin film) of Li 2 O 2 , eventually determining the battery performance. [12] For the solution-mediated pathway, disproportionation reaction of dissolved intermediate LiO 2 usually forms a large-size toroid-like Li 2 O 2 , resulting in a large discharge capacity but a high charge overpotential which is due to the limited contact between large-size discharge products and electrode surface. [3,12] For the surface adsorption pathway, electrode surface shows strong adsorption toward intermediate LiO 2 , finally leading to the deposition of thin film-like amorphous Li 2 O 2 on the oxygen electrode. The thin film-like Li 2 O 2 is in close contact with electrode, which is beneficial to reduce the charging overpotential. However, film-like discharge product will deliver a small discharge capacity because of the quickly passivated electrode surface. [13] As a result, designing porous oxygen electrodes with tuned adsorption capacity towards O-containing intermediates is essential for LOBs with both large discharge capacity and small charge overpotential. Generally, regulating the heterogeneous interfaces in the catalytic materials to realize the electronic modulation through interfacial coupling has proved to be an effective strategy for optimizing the chemical adsorption of the O-containing intermediates and accelerating the kinetics of oxygen electrode reactions. [14][15][16] Specifically, to achieve the thermodynamic equilibrium state, two regions of opposing charge distribution and a built-in electric field will be created at the interface of the heterostructure, where the strong charge region can modulate the adsorption of reactant, while the built-in Lithium-oxygen batteries (LOBs) with ultra-high theoretical energy density (≈3500 Wh kg −1 ) are considered as the most promising energy storage systems. However, the sluggish kinetics during the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) can induce large voltage hysteresis, inferior roundtrip efficiency and unsatisfactory cyclic stability. Herein, hydrangea-like NiO@Ni 2 P heterogeneous microspheres are elaborately designed as high-efficiency oxygen electrodes for LOBs. Benefitting from the interfacial electron redistribution on NiO@Ni 2 P heterostructure, the electronic structure can b...

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