Industrially profitable water splitting is one of the great challenges in the development of a viable and sustainable hydrogen economy. Alkaline electrolysers using Earth-abundant catalysts remain the most economically viable route to electrolytic hydrogen, but improved efficiency is desirable. Recently, electron spin polarization was described as a potential way to improve water-splitting catalysis. Here, we report the significant enhancement of alkaline water electrolysis when a moderate magnetic field (≤450 mT) is applied to the anode. Current density increments above 100% (over 100 mA cm −2) were found for highly magnetic electrocatalysts, such as the mixed oxide NiZnFe 4 O x. Magnetic enhancement works even for decorated Ni-foam electrodes with very high current densities, improving their intrinsic activity by about 40% to reach over 1 A cm −2 at low overpotentials. Thanks to its simplicity, our discovery opens opportunities for implementing magnetic enhancement in water splitting.

A sustainable future requires highly efficient energy conversion and storage processes, where electrocatalysis plays a crucial role. The activity of an electrocatalyst is governed by the binding energy towards the reaction intermediates, while the scaling relationships prevent the improvement of a catalytic system over its volcano-plot limits. To overcome these limitations, unconventional methods that are not fully determined by the surface binding energy can be helpful. Here, we use organic chiral molecules, i.e., hetero-helicenes such as thiadiazole-[7]helicene and bis(thiadiazole)-[8]helicene, to boost the oxygen evolution reaction (OER) by up to ca. 130 % (at the potential of 1.65 V vs. RHE) at state-of-the-art 2D Ni- and NiFe-based catalysts via a spin-polarization mechanism. Our results show that chiral molecule-functionalization is able to increase the OER activity of catalysts beyond the volcano limits. A guideline for optimizing the catalytic activity via chiral molecular functionalization of hybrid 2D electrodes is given.

Earth-abundant electrocatalysts for the oxygen evolution reaction (OER) able to work in acidic working conditions are elusive. While many first-row transition metal oxides are competitive in alkaline media, most of them just dissolve or become inactive at high proton concentrations where hydrogen evolution is preferred. Only noble-metal catalysts, such as IrO2, are fast and stable enough in acidic media. Herein, we report the excellent activity and long-term stability of Co3O4-based anodes in 1 M H2SO4 (pH 0.1) when processed in a partially hydrophobic carbon-based protecting matrix. These Co3O4@C composites reliably drive O2 evolution a 10 mA cm–2 current density for >40 h without appearance of performance fatigue, successfully passing benchmarking protocols without incorporating noble metals. Our strategy opens an alternative venue towards fast, energy efficient acid-media water oxidation electrodes.

Non-precious-metal catalysts are promising alternatives for Pt-based cathode materials in low-temperature fuel cells, which is of great environmental importance. Here, we have investigated the bifunctional electrocatalytic activity toward the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) of mixed metal (FeNi; FeMn; FeCo) phthalocyanine-modified multiwalled carbon nanotubes (MWCNTs) prepared by a simple pyrolysis method. Among the bimetallic catalysts containing nitrogen derived from corresponding metal phthalocyanines, we report the excellent ORR activity of FeCoN-MWCNT and FeMnN-MWCNT catalysts with the ORR onset potential of 0.93 V and FeNiN-MWCNT catalyst for the OER having E OER = 1.58 V at 10 mA cm –2 . The surface morphology, structure, and elemental composition of the prepared catalysts were examined with scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The FeCoN-MWCNT and FeMnN-MWCNT catalysts were prepared as cathodes and tested in anion-exchange membrane fuel cells (AEMFCs). Both catalysts displayed remarkable AEMFC performance with a peak power density as high as 692 mW cm –2 for FeCoN-MWCNT.

The electrochemical reduction of CO2 (eCO2RR) using renewable energy is an effective approach to pursue carbon neutrality. The eCO2RR to CO is indispensable in promoting C–C coupling through bifunctional catalysis and achieving cascade conversion from CO2 to C2+. This work investigates a series of M/N–C (M = Mn, Fe, Co, Ni, Cu, and Zn) catalysts, for which the metal precursor interacted with the nitrogen-doped carbon support (N–C) at room temperature, resulting in the metal being present as (sub)­nanosized metal oxide clusters under ex situ conditions, except for Cu/N–C and Zn/N–C. A volcano trend in their activity toward CO as a function of the group of the transition metal is revealed, with Co/N–C exhibiting the highest activity at −0.5 V versus RHE, while Ni/N–C shows both appreciable activity and selectivity. Operando X-ray absorption spectroscopy shows that the majority of Cu atoms in Cu/N–C form Cu0 clusters during eCO2RR, while Mn/, Fe/, Co/, and Ni/N–C catalysts maintain the metal hydroxide structures, with a minor amount of M0 formed in Fe/, Co/, and Ni/N–C. The superior activity of Fe/, Co/, and Ni/N–C is ascribed to the phase contraction and the HCO3 – insertion into the layered structure of metal hydroxides. Our work provides a facile synthetic approach toward highly active and selective electrocatalysts to convert CO2 into CO. Coupled with state-of-the-art NiFe-based anodes in a full-cell device, Ni/N–C exhibits >80% Faradaic efficiency toward CO at 100 mA cm–2.

The distinct beneficial effect of Zn-doping on the OER alkaline activity of Fe-based catalysts points towards an alternative and faster two-site mechanism.

The selectivity of CO2 electrolyzers has hitherto mainly been associated with the cathode selectivity. A few recent studies have shown that the nature of the polymer membrane can impact the system ionic selectivity, with anion exchange membranes (AEM) leading to high crossover of (bi)carbonates during operation and a CO2 pumping effect. In the present work, we investigate and compare CO2 crossover during operation through an AEM and a bipolar membrane (BPM) in a flow cell fed with gaseous CO2. With AEM, starting with 1 M KHCO3 catholyte and 1 M KOH anolyte, the anolyte pH rapidly drops from 14 to 8. This triggers an increase of 1.2 V in cell voltage at 45 mA·cm-2, due to increased OER overpotential and anolyte resistance. Steady-state operation at 45 mA·cm-2 with the AEM results in a CO2/O2 ratio of 3.6 at the anode. With BPM, the anolyte pH decreases more slowly, and the CO2/O2 ratio at the anode under steady-state at 45 mA·cm-2 is only 0.38. Overall, the cell voltage is lower with the BPM than with the AEM at steady-state. These results show the potential of BPMs to mitigate carbon crossover, which could be further reduced by optimizing their design.

The thermal hysteresis in the cooperative spin crossover (SCO) polymer [Fe(trz)(Htrz) 2 ] n [BF 4 ] n (1) has been tuned by a simple ball milling grinding process. Mechanical treatment affects the size and morphology of the crystallite domains, as confirmed by multiple complementary techniques, including ESEM, DLS, and PXRD data. Upon milling, the regular cubic shape particles recrystallize with slightly different unit cell parameters and preferential orientation. This macroscopic change significantly modifies the thermally induced SCO behavior, studied by temperature-dependent magnetic susceptibility, X-ray diffraction, and DSC analysis. Transition temperatures downshift, closer to room temperature, while hysteresis widens, when particle sizes are actually decreasing. We relate this counterintuitive observation to subtle modifications in the unit cell, offering new alternatives to tune and enhance SCO properties in this class of 1Dcooperative polymers.