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The advancement of highly-efficient, non-noble metal electrocatalysts with high active sites for oxygen evolution reaction (OER) continues to face severe challenges. In this work, a new 3D flower-like α-Co(OH) 2 catalyst with high Co–NH 2 active sites (referred to as α-Co(OH) 2 –NH 2) is prepared. The Co–NH 2 active sites are formed through the interactions between Co2+ and –NH 2 groups and exhibit higher electrocatalytic performance for OER in alkaline mediums, with a lower overpotential (300 mV at 10 mA cm−2), a flatter Tafel slope (75 mV dec−1) and a longer stability. Moreover, water splitting catalyzed by α-Co(OH) 2 –NH 2 delivers 1.62 V to reach a current density of 10 mA cm−2. The mechanism studies show that the OER electrocatalytic activity is closely related to the content of –NH 2. Density functional theory (DFT) calculations unveil that –NH 2 groups can facilitate the formation of OH∗ on the α-Co(OH) 2 surface and promote the desorption of O 2 ∗ into O 2(g). • A new type Co–NH 2 active sites in OER electrocatalyst was obtained by in-situ coordination strategy. • The electrocatalyst shows excellent OER activity and stability. • The OER electrocatalytic activity can be tuned by –NH 2 content. • Water splitting catalyzed by α-Co(OH) 2 –NH 2 delivers 1.62 V to reach a current density of 10 mA cm−2. [ABSTRACT FROM AUTHOR]

The development of electrocatalyst possessing superior oxygen reduction reaction (ORR) activity is highly desirable due to the low sluggish kinetics at the cathode of fuel cell. Here, CoFe 2 O 4 nanoparticles embedded in N-doped carbon nanotubes electrocatalyst (denoted as CoFe 2 O 4 -NC) is synthesized via polymerization of pyrrole, absorbing metal ion and annealing under Ar/NH 3 atmosphere. By in situ integrating the catalytically active CoFe 2 O 4 nanoparticles with the N-doped carbon nanotubes and enhancing electrical conductivity, the as-obtained electrocatalyst exhibits excellent ORR activity and long-term stability with a half-wave potential of 0.86 V and 10 h continuous cycling, outperforming the reported similar catalysts. This work opens a new path for the expansion of low cost and efficient ORR electrocatalysts to substitute Pt-based metals for energy storage and conversion devices. [Display omitted] • In situ synthesis of CoFe 2 O 4 nanoparticles embedded in N-doped carbon nanotubes. • CoFe 2 O 4 -NC exhibits excellent ORR activity with a half-wave potential of 0.86 V and long-term stability. • The immobilization of particles on carbon tube prevents the CoFe 2 O 4 nanoparticles from dissolving or aggregating. [ABSTRACT FROM AUTHOR]

Recently, to improve the catalytic activity of oxygen evolution reaction (OER) electrocatalysts, some design strategies, such as the decrease of the catalyst particle size, the formation of the porous structure and the couple of carbon-based materials, are receiving increased attention in energy-related systems. Herein, based on metal organic framework (MOF), we develop an effective strategy to synthesize Ni nanoparticles embedded in N doped carbon nanotubes (Ni NPs@N-CNTs) catalyst. In consequence, the Ni NPs@N-CNTs integrates the advantageous features of NPs and N-CNTs towards OER, such as more catalytic sites, large surface area, pore-rich structure and good electrical conductivity. Benefiting from the favorable features, the Ni NPs@N-CNTs exhibits a better OER performance than commercial RuO 2 in alkaline medium, which includes a lower onset potential (1.49 V), a smaller Tafel slope (106 mV dec −1 ). The present work opens a new window for the construction of the coupling materials between NPs and carbon-based materials to increase the electrocatalytic activity of transition metal catalysts. [ABSTRACT FROM AUTHOR]

Interfacial charge transfer efficiency and electronic states of active sites are two essential issues to restrict catalytic activity of electrocatalysts for oxygen evolution reaction (OER). In this work, we show that although Au is recognized to be inert towards OER, the catalytic activity of Fe 3 O 4 catalyst for OER was highly boosted by coupling Fe 3 O 4 with Au to address these two issues. Here, Au nanoparticles were attached to hierarchical Fe 3 O 4 microsphere through electrochemical deposition, a mild and rapid approach that can be accomplished within 3 min and requires no sophisticated equipment. With the coupling of Au, interfacial charge transfer resistance of Fe 3 O 4 declined remarkably. On the other hand, oxidability of Fe sites and electron accepting capability of Au sites was elevated due to strong interaction between Au and Fe 3 O 4. Owing to these two merits induced by Au, Fe 3 O 4 exhibited enhanced catalytic activity for OER. The potential of Fe 3 O 4 to obtain 10 mA/cm2 decreased by 640 mV, the current density was amplified up to 2.5 fold at the potential of 2 V (vs SCE), and the Tafel slop was reduced by 146 mV/dec. This work shows that the catalytic activity of an earth-abundant electrocatalyst (Fe 3 O 4) for OER reaction was boosted by coupling it with OER-inert Au. It is found that the coupling of Au not only facilitated charge transfer efficiency of the catalyst, but elevated the oxidability of Fe sites and electron accepting capability of Au sites. Thereby, when coupled with Au, Fe 3 O 4 exhibited enhanced current density, reduced overpotential, and smaller Tafel slop. [Display omitted] • Enhance catalytic activity of Fe 3 O 4 for OER reaction via coupling of OER-inert Au. • Effectively promoted interfacial charge transfer with the decoration of Au. • Modify the state of Fe sites and Au sites by strong interaction of Au with Fe 3 O 4. • An easy-to-handle and rapid way to couple Au with hierarchical Fe 3 O 4 microspheres. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting is considered as a promising approach to storing renewable electricity in the form of hydrogen fuel. In this work, we report the design and electrocatalytic properties of chiral CuO@Ni with three dimensional (3D) continuous macroporous framework. With the chiral CuO@Ni as anode, the OER overpotential required to achieve the current density of 10 mA/cm2 was as low as 110 mV in 0.1 M KOH electrolyte, and the hydrogen production rate of water splitting reaction could reach 1070 nL/s. Moreover, the OER overpotential could be regulated easily by controlling the deposition time of chiral CuO layer on Ni. The high catalytic activity of chiral CuO@Ni for water splitting is closely associated with the Chiral-induced spin selectivity ( CISS ) effect, the large reactive area provided by its 3D macroporous structure, and the effective cooperation between chiral CuO and Ni foam that facilitated the transportation of spin aligned electrons from chiral CuO layer to Ni. The results shown in this work indicate a simple and promising strategy to improve the electrocatalytic activity of other chiral earth-abundant catalysts for water splitting. This work shows the design and properties of chiral CuO@Ni with three dimensional continuous macroporous framework. The chiral CuO@Ni exhibited lower OER overpotential and larger current density than many CuO-based catalysts. Its high catalytic activity for water splitting reaction is attributed to the CISS effect of chiral CuO, the large reactive area of its 3D porous structure, and the synergistic interaction between the chiral CuO and the Ni foam. Image 1 • Chiral CuO@Ni with three dimensional continuous macroporous framework. • Low OER overpotential (110 mV) to achieve 10 mA/cm2 current density. • Easy and effective way to enhance the activity of chiral earth-abundant catalyst. [ABSTRACT FROM AUTHOR]

At present, the preparation of highly active, long-term durable, and low cost electrocatalysts toward oxygen evolution reaction is still a challenge for energy conversion and storage. This work reports CoS 1.097 embedded in flower-like biomass derived from red blood cells (RBCs) nanocatalyst, was synthesized via a one-step, hydrothermal method. Compared to pure CoS 1.097 microspheres, the generated flower-like CoS 1.097 -biomass (CoS 1.097 -B) nanosheets exhibits enhanced OER electrocatalytic activity with a onset potential of 1.43 V (vs. RHE), an overpotential of 260 mV at the current density of 10 mA cm−2, and a low Tafel slope of 83 mV dec−1. Moreover, the CoS 1.097 -B displays good OER stability with little decrease after 400 cycles. Our work provides a reference for designing catalysts with high activity and good stability using biomass under mild conditions. Image 1 • Novel synthesis of CoS 1.097 embedded in flower-like biomass nanocatalysts. • More exposed CoS 1.097 particles impart large active area. • The CoS 1.097 -B exhibits excellent activity and stability towards OER. • The CoS 1.097 -B requires an overpotential of 260 mV to reach a current density of 10 mA cm−2. • The Tafel slope of CoS 1.097 -B is only 83 mV dec−1. [ABSTRACT FROM AUTHOR]

Microbial electrolysis cells (MECs) are a promising approach for producing hydrogen gas from low-grade substrates with low energy consumption. However, pH increase in a cathode due to proton reduction and thus the need for buffering this pH increase remains a challenge for MEC operation. In this study, a previously reported operational strategy for pH buffer - periodic polarity reversal (PPR) was further studied by developing and applying an automatically control system. The effect of PPR interval on the hydrogen production was investigated and the optimal PPR interval was determined. With an optimal PPR interval of 40 min, the MEC had a significantly low pH increase rate of 0.0085 min −1 in its cathodes, and this resulted in the highest current density of 1.58 ± 0.02 A m −2 , Coulombic efficiency of 130.3 ± 1.8%, hydrogen production rate of 1.65 ± 0.01 m 3 H 2 m −3 d −1 , overall hydrogen recovery of 75.9 ± 0.4%, and energy efficiency relative to the substrate input of 140.8 ± 1.4%. Further analysis suggested that this optimal value of PPR interval was affected by both reaction time and hydrogen supply. When the PPR interval increased from 10 min to 40 min, a longer reaction time helped produce more protons and thus generated a stronger buffer capacity. Beyond 40 min, the mass transfer of the dissolved hydrogen gas could become a limiting factor, leading to a weaker buffer capacity with a longer PPR interval. Those findings have provided an effective pH control strategy with a convenient control system for maximizing hydrogen production in MECs. [ABSTRACT FROM AUTHOR]