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Electrocatalysis enables the industrial transition to sustainable production of chemicals using abundant precursors and electricity from renewable sources. De-centralized production of hydrogen peroxide (H2O2) from water and oxygen of air is highly desirable for daily life and industry. We report an effective electrochemical refinery (e-refinery) for H2O2 by means of electrocatalysis-controlled comproportionation reaction (2(H)O + O -> 2(HO)), feeding pure water and oxygen only. Mesoporous nickel (II) oxide (NiO) was used as electrocatalyst for oxygen evolution reaction (OER), producing oxygen at the anode. Conducting polymer poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) drove the oxygen reduction reaction (ORR), forming H2O2 on the cathode. The reactions were evaluated in both half-cell and device configurations. The performance of the H2O2 e-refinery, assembled on anion-exchange solid electrolyte and fed with pure water, was limited by the unbalanced ionic transport. Optimization of the operation conditions allowed a conversion efficiency of 80%., Funding: Swedish Agency for Innovation Systems (Vinnova) [2016-05156]; Swedish Energy Agency [42022-1]; Swedish Research Council [VR 2021-04427, VR 2019-05577, VR 2016-05990]; Centre in Nanoscience and Technology (CeNano, Linkoeping Institute of Technology (LiTH), Linkoeping University, 2020, 2021); Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoeping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Knut and Alice Wallenberg Foundation (H2O2) [KAW 2018.0058]

Inspired by thermally sensitive ion channels in human skin, a polarized membrane composed of a ferroelectric polymer fiber matrix is used to double the heat-induced potential in ionic thermoelectric devices. The comparison of the thermal potentials between different directions of polarization and temperature gradient indicates the importance of cation-dipole interactions for the enhancement. Adding a polarized membrane to ionic thermoelectric devices induces dipole-ion interaction and enhances the thermal voltage by more than double., Funding Agencies|EU commission [101058284]; Swedish Research Council [VR 2018-04037]; AForsk Foundation [23-220]; Advanced Functional Materials Centerat Linko ping University

The quest for eco-friendly materials with anticipated positive impact for sustainability is crucial to achieve the UN sustainable development goals. Classical strategies of composite materials can be applied on novel nanomaterials and green materials. Besides the actual technology and applications also processing and manufacturing methods should be further advanced to make entire technology concepts sustainable. Here, they show an efficient way to combine two low-cost materials, cellulose and zinc oxide (ZnO), to achieve novel functional and "green" materials via paper-making processes. While cellulose is the most abundant and cost-effective organic material extractable from nature. ZnO is cheap and known of its photocatalytic, antibacterial, and UV absorption properties. ZnO nanowires are grown directly onto cellulose fibers in water solutions and then dewatered in a process mimicking existing steps of large-scale papermaking technology. The ZnO NW paper exhibits excellent photo-conducting properties under simulated sunlight with good ON/OFF switching and long-term stability (90 minutes). It also acts as an efficient photocatalyst for hydrogen peroxide (H2O2) generation (5.7 x 10(-9) m s(-1)) with an envision the possibility of using it in buildings to enable large surfaces to spontaneously produce H2O2 at its outer surface. Such technology promise for fast degradation of microorganisms to suppress the spreading of diseases., Funding Agencies|Knut and Alice Wallenberg Foundation; VINNOVA (Digital Cellulose Center); Vetenskapradet [2016-05990]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoeping University [2009-00971]; aForsk Foundation [17-433]

“Water-in-polymer salt” electrolytes (WiPSEs) based on potassium polyacrylate (PAAK) belong to a new family of “water-in-salt” electrolytes that is envisioned as a potential solution for large-scale supercapacitors to balance the electric grid at short time scales. The WiPSEs display a broad electrochemical stability window up to 3 V, yet they are nonflammable and provide high ionic conductivity (100 mS/cm) as required in high-power devices. However, the transport of matter in PAAK-based WiPSEs has not been studied. In this work, we have extensively characterized PAAK by spectroscopic methods such as Raman spectroscopy and NMR diffusometry to determine the state of water and elucidate the mechanism of ionic transport as well as its interplay with water and polymer chain dynamics, which reveals that a significant proportion of the transport in WiPSEs is attributed to hydrated cations. The results are further supported by molecular dynamics (MD) simulations. Finally, the potential of WiPSEs based on PAAK is demonstrated in an activated carbon-based supercapacitor operating up to 2 V with reasonable self-discharge. This proof of concept shows promise for low-cost and large-scale supercapacitors., Funding Agencies|Swedish Energy Agency [P52023-1]; Knut and Alice Wallenberg Foundation [21-130]; Swedish Electricity Storage and Balancing Centre (SESBC); Swedish Energy Agency together with 5 academic and 26 non-academic partners; Ligna Energy; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University; Swedish Research Council; STandUP for Energy collaboration; [KAW 2020.0174]; [22-134]; [2009-00971]; [2020-05223]

Intrinsically stretchable energy storage devices are essential for the powering of imperceptible wearable electronics. Organic batteries based on plant-derived redox-active molecules can offer critical advantages from a safety, sustainability, and economic perspective, but such batteries are not yet available in soft and stretchable form factors. Here we report an intrinsically stretchable organic battery made of elastomeric composite electrodes formulated with alizarin, a natural dye derived from the plant Rubia tinctorum, whose two quinone motifs enable its uses in both positive and negative electrodes. The quaternary biocomposite electrodes possess excellent electron-ion conduction/coupling and superior stretchability (>300%) owing to self-organized hierarchical morphology. In a full-cell configuration, its energy density of 3.8 mW h cm−3 was preserved at 100% strain, and assembled modules on stretchy textiles and rubber gloves can power integrated LEDs during various deformations. This work paves the way for low-cost, eco-friendly, and deformable batteries for next generation wearable electronics., We thank Mohsen Mohammadi, Sangmin Park, and Dr Robert Brooke for assistance with illustrations, Meysam Karami Rad for LabVIEW programming and help with the circuit tests, and Laura Seufert for assistance with the module demonstration. This work was financially supported by the ÅForsk Foundation (19-428), the Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linköping University (Faculty grant SFO-Mat-LiU no. 2009-00971), the Knut and Alice Wallenberg Foundation (POC “paper batteries” and “high voltage aqueous electrolyte”), and the Swedish Research Council (starting grant no. 2020-05218, no. 2019-04424 and no. 2016-06146). G. G. acknowledges financial support from the Swedish Research Council (no. 2018-03957) and the Swedish Energy Agency grant 51201-1. A. R. acknowledges Marie Skłodowska-Curie Actions Seal of Excellence Fellowship program from the Sweden's Innovation Agency (Vinnova grant no. 2021-01668). This work was partially supported by the Wallenberg Initiative Materials Science for Sustainability (WISE) funded by the Knut and Alice Wallenberg Foundation.

Soft vibrotactile devices have the potential to expandthe functionalityof emerging electronic skin technologies. However, those devices oftenlack the necessary overall performance, sensing-actuation feedbackand control, and mechanical compliance for seamless integration onthe skin. Here, we present soft haptic electromagnetic actuators thatconsist of intrinsically stretchable conductors, pressure-sensitiveconductive foams, and soft magnetic composites. To minimize jouleheating, high-performance stretchable composite conductors are developedbased on in situ-grown silver nanoparticles formed within the silverflake framework. The conductors are laser-patterned to form soft anddensely packed coils to further minimize heating. Soft pressure-sensitiveconducting polymer-cellulose foams are developed and integrated totune the resonance frequency and to provide internal resonator amplitudesensing in the resonators. The above components together with a softmagnet are assembled into soft vibrotactile devices providing high-performanceactuation combined with amplitude sensing. We believe that soft hapticdevices will be an essential component in future developments of multifunctionalelectronic skin for future human-computer and human-roboticinterfaces.

Zn-metal batteries (ZnBs) are safe and sustainable because of their operability in aqueous electrolytes, abundance of Zn, and recyclability. However, the thermodynamic instability of Zn metal in aqueous electrolytes is a major bottleneck for its commercialization. As such, Zn deposition (Zn2+ & RARR; Zn(s)) is continuously accompanied by the hydrogen evolution reaction (HER) (2H(+) & RARR; H-2) and dendritic growth that further accentuate the HER. Consequently, the local pH around the Zn electrode increases and promotes the formation of inactive and/or poorly conductive Zn passivation species (Zn + 2H(2)O & RARR; Zn(OH)(2) + H-2) on the Zn. This aggravates the consumption of Zn and electrolyte and degrades the performance of ZnB. To propel HER beyond its thermodynamic potential (0 V vs standard hydrogen electrode (SHE) at pH 0), the concept of water-in-salt-electrolyte (WISE) has been employed in ZnBs. Since the publication of the first article on WISE for ZnB in 2016, this research area has progressed continuously. Here, an overview and discussion on this promising research direction for accelerating the maturity of ZnBs is provided. The review briefly describes the current issues with conventional aqueous electrolyte in ZnBs, including a historic overview and basic understanding of WISE. Furthermore, the application scenarios of WISE in ZnBs are detailed, with the description of various key mechanisms (e.g., side reactions, Zn electrodeposition, anions or cations intercalation in metal oxide or graphite, and ion transport at low temperature)., Funding Agencies|Knut and Alice Wallenberg (KAW) foundation [KAW 2020.0174]; Wallenberg Initiative Materials Science for Sustainability WISE; Swedish Energy Agency (SESBC competence center) [P52023-1, 526701]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoeping University (Faculty Grant SFO-Mat-LiU ) [2009-00971]; Aforsk foundation [21-130, 22134]

The interfacial energetics are known to play a crucial role in organic diodes, transistors, and sensors. Designing the metal-organic interface has been a tool to optimize the performance of organic (opto)electronic devices, but this is not reported for organic thermoelectrics. In this work, it is demonstrated that the electrical power of organic thermoelectric generators (OTEGs) is also strongly dependent on the metal-organic interfacial energetics. Without changing the thermoelectric figure of merit (ZT) of polythiophene-based conducting polymers, the generated power of an OTEG can vary by three orders of magnitude simply by tuning the work function of the metal contact to reach above 1000 mu W cm(-2). The effective Seebeck coefficient (S-eff) of a metal/polymer/metal single leg OTEG includes an interfacial contribution (V-inter/Delta T) in addition to the intrinsic bulk Seebeck coefficient of the polythiophenes, such that S-eff = S + V-inter/Delta T varies from 22.7 mu V K-1 [9.4 mu V K-1] with Al to 50.5 mu V K-1 [26.3 mu V K-1] with Pt for poly(3,4-ethylenedioxythiophene):p-toluenesulfonate [poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)]. Spectroscopic techniques are used to reveal a redox interfacial reaction affecting locally the doping level of the polymer at the vicinity of the metal-organic interface and conclude that the energetics at the metal-polymer interface provides a new strategy to enhance the performance of OTEGs., Funding Agencies|Knut and Alice Wallenberg Foundation; EU [ESR 955837_HORATES]; Swedish Research Council [2016-06146, 2016-03979]; Forsk [18-313]; Academy of Finland Postdoctoral Researcher [340103]; EU H2020 Marie Sklodowska-Curie [101022777]; Swedish Foundation for Strategic Research (SiOS); Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoeping University [2009-00971]

Ionic thermoelectric materials can generate large thermal voltages under temperature gradients while also being low-cost and environmentally friendly. Many electrolytes with large Seebeck coefficients are reported in recent years, however, the mechanism of the thermal voltage is remained elusive. In this work, three types of polyelectrolytes are studied with different cations and identified a significant contribution to their thermal voltage originating from a concentration gradient. This conclusion is based on studies of the loss and gain of water upon temperature changes, variations in conductivity with water content and temperature, and the voltages induced by changes in water content. The results are analyzed by the "hopping mode" dynamics of charge transport in electrolytes. The hydration of different cations influences the water concentration gradient, which affects the barrier height and ion-induced potential in the electrodes. This work shows that the hydro-voltage in ionic thermoelectric devices can be one order of magnitude larger than the contribution from thermodiffusion-induced potentials, and becomes the main contributor to energy harvesting when implemented into ionic thermoelectric supercapacitors. Together with the rationalized theoretical discussion, this work clarifies the mechanism of thermal voltages in electrolytes and provides a new path for the development of ionic thermoelectric materials. The thermal voltage of polyelectrolyte films largely depends on the water concentration gradient under a temperature difference, which can be optimized to promote the generated total voltage up to over 30 mV K-1.image, Funding Agencies|EU commission [101058284]; Swedish Research Council [VR 2018-04037]; AForsk Foundation [23-220]; Advanced Functional Materials Center at Linkoping University [2009-00971]

Lignin, obtained as a waste product in huge quantities from the large-scale cellulose processing industries, holds a great potential to be used as sustainable electrode material for large-scale electroactive energy storage systems. The fixed number of redox-active phenolic groups present within the lignin structure limits the electrochemical performance and the total energy storage capacity of the lignin-based electrodes. Herein, the way to enhance the charge storage capacity of lignin by incorporating additional small catechol molecules into the lignin structure is demonstrated. The catechol derivatives are covalently attached to the lignin via aromatic electrophilic substitution reaction. The increased phenolic groups in all functionalized lignin derivatives notably increase the values of capacitance compared to pristine lignin. Further, solvent fractionation of lignin followed by functionalization using catechol boosts three times the charge capacity of lignin electrode. Herein, a scalable, cost-effective method to enhance the electrochemical performance of lignin electrodes via incorporation of small redox active moieties into the lignin structure is demonstrated. Solvent fractionation of lignin followed by functionalization using catechol increases the charge storage capacity of the lignin-carbon composite electrode by a factor of 3 reaching record high charge capacity above 100 mAh g-1., Funding Agencies|Knut and Alice Wallenberg Foundation [KAW 2020-0174]; Wallenberg Wood Science Center; Swedish Energy Agency [P52023-1]; Forsk Foundation [22-134]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoeping University [2009-00971]

Internet-of-Everything (IoE) is defined as networked connections of things, people, data, and processes. IoE nodes, preferably shaped as printed flexible systems, serve as the frontier outpost of the Internet and comprise devices to record and regulate states and functions. To power distributed IoE nodes in an ecofriendly manner, a technology to scavenge energy from ambience and self-powered devices is developed. For this, piezoelectricity is regarded as a key property; however, the current technology typically based on polyvinylidene difluoride (PVDF) copolymers is expensive and produced via toxic protocols. We report piezoelectric characteristics of electrochemically poled cellulose nanofiber (CNF) thin films processed from water dispersions. Poling these films under humid conditions causes breaking and reorientation of CNF segments, which results in enhanced crystal alignment rendering the resulting material piezoelectric. Generators based on poled CNF show similar piezoelectric voltage and coefficient, here measured as d(33) = 46 pm V-1, to devices including PVDF copolymer layers of similar thickness. Our findings promise low-cost and printable ecofriendly piezoelectric-powered IoE nodes., Funding Agencies|Knut and Alice Wallenberg Foundation; Swedish Research Council [2016-06146, 2018- 04037, 2009-00971]; NCD- SWEET beamline of ALBA synchrotron in Barcelona, Spain; [VR 2016-05990]

Lignin, a byproduct from the pulp industry, is one of the redox active biopolymers being investigated as a component in the electrodes for sustainable energy storage applications. Due to its insulating nature, it needs to be combined with a conductor such as carbon or conducting polymer for efficient charge storage. Here, the lignin/carbon composite electrodes manufactured via mechanical milling (ball milling) are reported. The composite formation, correlation between performance and morphology is studied by comparison with manual mixing and jet milling. Superior charge storage capacity with approximate to 70% of the total contribution from the Faradaic process involving the redox functionality of lignin is observed in a mechanically milled composite. In comparison, manual mix shows only approximate to 30% from the lignin storage participation while the rest is due to the electric double layer at the carbon-electrolyte interface. The significant participation of lignin in the ball milled composite is attributed to the homogeneous, intimate mixing of the carbon and the lignin leading the electronic carrier transported in the carbon phase to reach most of the redox group of lignin. A maximum capacity of 49 mAh g(-1) is obtained at charge/discharge rate of 0.25 A g(-1) for the sample milled for 60 min., Funding Agencies|Knut and Alice Wallenberg Foundation [KAW 2019-0344, KAW 2020-0174]; Wallenberg Wood Science Center; Vetenskapradet [2016-05990]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoeping University [2009-00971]; Wallenberg Scholar grants

Zn-ion batteries are one of the hot candidates for low-cost and sustainable secondary batteries. The hydrogen evolution and dendritic growth upon zinc deposition are todays challenges for that technology. One of the new strategies to cope with these issues is to use "water-in-salt" electrolyte (WISE), that is, super concentrated aqueous electrolytes, to broaden its electrochemical stability window (ESW), suppressing hydrogen evolution reaction (HER), and perturbing the dendritic growth. Herein, this work proposes to use "water-in-polymer salt" electrolyte (WIPSE) concept to mitigate the challenges with Zn ion batteries and bring this technology toward one of the cheapest, greenest, and most sustainable electrodes: Lignin-carbon (L-C) electrode. Potassium polyacrylate (PAAK) as WISE bears out as better electrolyte for L-C electrodes in terms of self-discharge, cyclic stability, and specific capacity compared to conventional electrolyte based on chemically cousin molecule potassium acetate. Zinc bis(trifluoromethanesulfonyl) imide (Zn(TFSI)(2)) added into WIPSE shows deposition and dissolution of Zn in Zn//Zn symmetric cell suggesting that Zn2+ are moving into the polyanionic network. Furthermore, the added bis (trifluor omethanesul fonyl) imide (TFSI-) metal salts trigger a approximate to 40% enhancement of the capacity of L-C electrode. These results show a new promising direction toward the development of cost-effective and sustainable Zn-lignin batteries., Funding Agencies|Knut and Alice Wallenberg (KAW) foundation [KAW 2020.0174]; Swedish Research Council [2016-05990]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoeping University [2009-00971]; competence center FunMat-II - Swedish Agency for Innovation Systems (Vinnova) [2016-05156]; aforsk foundation [21-130]; KAW

Desalination by capacitive deionization (CDI) is a promising technique to combine desalination and energy storage. The efficiency of charge storage process, which is equivalent to the desalination process, depends strongly on the presence of Faradic side reactions on the electrode. Herein, the performance of a new low-cost designed flow-through electrode with porous carbon nanoparticles (CP) coating on carbon-fiber paper (CFP) is evaluated. The CP layer enables high capacitance while the CFP core makes fluid dynamics along and across the electrode. The electrodes are evaluated by studying the effective operational CDI parameters, such as operational voltage, degassing of electrolyte, and salt concentration. The Faradic side reaction and its effect on charge efficiency (CE) are evaluated which are estimated to decrease to 46% by liquid flow bringing dissolved oxygen from the air-electrolyte interface to the electrode. The CE enhances to 59% with a salt concentration of 1 m. By purging N-2 gas, CE is much higher (>85%) with a maximum efficiency of 97% at 0.6 V. Three regimes of the complex kinetic of side reactions are found involving various species such as O-2, H2O2, H-2, and carbon oxidation and the implication of those regimes for real applications are discussed., Funding Agencies|Swedish Research Council [VR 2016-05990]; Knut and Alice Wallenberg Foundation [KAW 2018.0058]; Swedish Energy Agency [P52023-1]; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoeping University [2009-00971]

Sustainable production of hydrogen gas, a green energy carrier of high density, is possible only by electrolysis of water based on the hydrogen evolution reaction (HER). Here, we report the effect of oxygen poisoning on the efficiency of hydrogen production and the consumption by the HER and the hydrogen oxidation reaction (HOR), respectively, on the interface of platinum group metal-free electrocatalyst TaS2 in pristine form and intercalated by the organic Lewis base hexylamine. The state of the surface probed by photoelectron spectroscopy was significantly altered by both Lewis base doping and oxygen poisoning. This alteration dramatically affects the hydrogen production efficiency in the HER, while the back process by the HOR was less sensitive to the changes in the surface states of the electrocatalysts. The oxygenated and intercalated electrocatalyst shows more than 2 x 105 times lower exchange current density of the HER compared to pristine oxygenated materials., Funding Agencies|Swedish Research Council [VR 2016-05990, VR 2020-04210]; Knut and Alice Wallenberg Foundation [KAW 2019.0604, 2021.0195]; Karl Erik O nnesjoes Foundation; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoeping University (Faculty Grant SFO-Mat-LiU) [2009-00971]

Ionic thermoelectric supercapacitors (ITESCs) produce orders of magnitude higher voltages than those of con-ventional thermoelectrics (TEs) based on the thermo-diffusion of electrons/holes and are therefore attractive for converting low-grade heat into electricity. The stretchability and stability of the whole ITESC are important for wearable heat harvesting applications. Recent studies on ITESC have focused on stretchable ionic TE electrolytes with a giant Seebeck coefficient, but there are no reports of fully stretchable ITESCs for wearable heat harvesting devices due to the lack of stretchable electrodes and stretchable ionic TE electrolytes with stability. Herein, we present a fully stretchable ITESC composed of stable high-performance ionic thermoelectric elastomer (ITE) electrolyte and stretchable gold nanowire (AuNW) electrodes. The ITE shows excellent air stability (> 60 d) in comparison to hydrogel-based electrolytes that are susceptible to dehydration in ambient conditions. Further-more, the ITE exhibits an apparent thermopower up to 38.9 mV K-1 and ionic conductivity of 3.76 x 10-1 mS cm-1, which both are maintained up to a tensile strain of 250%. Finally, a fully stretchable ITESC with AuNW electrodes is developed which can harvest energy from thermal gradients during deformations., Funding Agencies|National Research Foundation (NRF) of Korea - Korea government (MSIT) [2021R1I1A1A01048298]; Korea Initiative for fostering University of Research and Innovation (KIURI) Program of the NRF - Korean government (MSIT) [NRF-2020M3H1A1077207]; European Union [101064482]; NRF of Korea - Korea government (MIST); NRF of Korea [2020R1A2B5B03002697]; National Research Foundation of Korea [2021R1I1A1A01048298] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)

Electrocatalysis enables the industrial transition to sustainable production of chemicals using abundant precursors and electricity from renewable sources. De-centralized production of hydrogen peroxide (H2O2) from water and oxygen of air is highly desirable for daily life and industry. We report an effective electrochemical refinery (e-refinery) for H2O2 by means of electrocatalysis-controlled comproportionation reaction (2(H)O + O -> 2(HO)), feeding pure water and oxygen only. Mesoporous nickel (II) oxide (NiO) was used as electrocatalyst for oxygen evolution reaction (OER), producing oxygen at the anode. Conducting polymer poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) drove the oxygen reduction reaction (ORR), forming H2O2 on the cathode. The reactions were evaluated in both half-cell and device configurations. The performance of the H2O2 e-refinery, assembled on anion-exchange solid electrolyte and fed with pure water, was limited by the unbalanced ionic transport. Optimization of the operation conditions allowed a conversion efficiency of 80%., Funding: Swedish Agency for Innovation Systems (Vinnova) [2016-05156]; Swedish Energy Agency [42022-1]; Swedish Research Council [VR 2021-04427, VR 2019-05577, VR 2016-05990]; Centre in Nanoscience and Technology (CeNano, Linkoeping Institute of Technology (LiTH), Linkoeping University, 2020, 2021); Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoeping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Knut and Alice Wallenberg Foundation (H2O2) [KAW 2018.0058]

Practical interest in oxygen reduction reaction (ORR) has traditionally been due to its application at fuel cells' cathode following its complete 4e route to the water. In search of new electrode materials, it was discovered that conducting polymers (CPs) also are capable of driving ORR, though predominantly halting the process at 2e reduction leading to hydrogen peroxide generation. As alternative ways to produce this "green oxidant" are attracting increasing attention, a detailed study of the ORR mechanism at CP electrodes gains importance. Here, we summarize our recent theoretical work on the topic, which underscores the fundamental difference between CP and electrocatalytic metal ORR electrodes. Our insights also bring to us the attention of outer-sphere electron transfer, not unknown but somewhat ignored in the field. We also put the action of CP electrodes in a more general context of chemical ORR and redox mediation responsible for the electrocatalytic ORR mechanism., Funding Agencies|Wallenberg Wood Science Center; Swedish Research Council [VR 2019-05577]; Flexible metalair primary batteries [VR 2016-05990]; Paper fuel cell; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoping University [2009-00971]; Knutoch Alice Wallenbergs Stiftelse