Search

Exploration of active and durable electrocatalysts for water splitting has aroused widespread concern and is devoted with huge efforts to produce sustainable energy: hydrogen. Herein, self-standing RuO2-NiO nanosheets on conductive nickel foam (RuO2-NiO NSs/NF) are obtained via a spontaneous coprecipitation strategy for the hydrogen evolution reaction (HER). The RuO2-NiO NSs/NF electrode not only has efficient intrinsic activity because of the in situ-formed Ru/RuO2 interface during HER but also presents superior kinetic stability due to the self-standing nanosheet structure. By integrating compositional and structural merits, the RuO2-NiO NSs/NF electrode displays higher turnover frequencies compared with Pt/C (0.524 vs 0.376 H2 s–1 in 1 M KOH and 0.177 vs 0.065 H2 s–1 in 1 M KPi) and delivers remarkably small overpotentials of 14 and 25 mV at 10 mA cm–2 in 1 M KOH and KPi, respectively. Along with long-term stability at large current densities and excellent regenerative capability with simple acid treatment, the RuO2-NiO NSs/NF electrode exhibits potential for commercial seawater splitting. [ABSTRACT FROM AUTHOR]

Realizing efficient hydrogenation of N 2 molecules in the electrocatalytic nitrogen reduction reaction (NRR) is crucial in achieving high activity at a low potential because it theoretically requires a higher equilibrium potential than other steps. Analogous to metal hydride complexes for N 2 reduction, achieving this step by chemical hydrogenation can weaken the potential dependence of the initial hydrogenation process. However, this strategy is rarely reported in the electrocatalytic NRR, and the catalytic mechanism remains ambiguous and lacks experimental evidence. Here, we show a highly efficient electrocatalyst (ruthenium single atoms anchored on graphdiyne/graphene sandwich structures) with a hydrogen radical-transferring mechanism, in which graphdiyne (GDY) generates hydrogen radicals (H • ), which can effectively activate N 2 to generate NNH radicals ( • NNH). A dual-active site is constructed to suppress competing hydrogen evolution, where hydrogen preferentially adsorbs on GDY and Ru single atoms serve as the adsorption site of • NNH to promote further hydrogenation of NH 3 synthesis. As a result, high activity and selectivity are obtained simultaneously at -0.1 V versus a reversible hydrogen electrode. Our findings illustrate a novel hydrogen transfer mechanism that can greatly reduce the potential and maintain the high activity and selectivity in NRR and provide powerful guidelines for the design concept of electrocatalysts.

It is highly challenging to design low-cost, efficient electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, a hierarchical heterostructure was constructed on three-dimensional (3D) Ni foam, which contains Ni 3 S 2 nanorods decorated with both Co 9 S 8 and amorphous MoS x nanosheets and Ni 3 S 2 nanowires decorated with amorphous MoS x nanosheets, namely, MoS x @Co 9 S 8 @Ni 3 S 2 /NF. The synergistic effects from the strong interactions of the heterointerface and unique hierarchical heterostructure endow the MoS x @Co 9 S 8 @Ni 3 S 2 /NF with abundant active sites and effective mass and electron transport pathways, resulting in excellent activity toward both HER and OER in 1 M KOH. It only gives a low overpotential of 76.5 mV to achieve 10 mA cm -2 for HER and a low overpotential of 310 mV to achieve 100 mA cm -2 for OER. Based on the superior catalytic activity of MoS x @Co 9 S 8 @Ni 3 S 2 /NF for OER and HER, we demonstrated the activity of overall water splitting using MoS x @Co 9 S 8 @Ni 3 S 2 /NF as both the anode and cathode. It shows a higher catalytic activity for overall water splitting with a low cell voltage of 1.52 V at 10 mA cm -2 than commercial Pt/C/NF||IrO 2 /NF (1.61 V) and superior stability. This work provides a platform for the design and preparation of efficient electrocatalysts with various hierarchical heterostructures.

The oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are considered to be cornerstones of many energy conversion and storage technologies. It is difficult studying high-performance nonprecious materials as cost-effective bifunctional electrocatalysts for both the OER and ORR in future practical applications. In this study, NiCo 2 S 4 hollow spheres (NiCo 2 S 4 HSs) were fabricated via an effective and facile one-pot "green" approach in an N, N-dimethylformamide-ethylene glycol binary solution. The obtained NiCo 2 S 4 HSs had a high specific surface area as well as numerous active sites and showed a remarkable catalytic performance and durability toward both the OER and ORR in an alkaline electrolyte. For the ORR, NiCo 2 S 4 HSs exhibited a positive half-wave potential of 0.80 V and demonstrated outstanding stability and enhanced methanol tolerance. For the OER, NiCo 2 S 4 HSs presented a low overpotential (400 mV) at a current density of 10 mA cm -2 , small Tafel slope, and excellent stability in 0.1 M KOH. Moreover, regarding the overall electrocatalytic activity, the potential difference of NiCo 2 S 4 HSs was 0.83 V, surpassing that of NiCo 2 S 4 nanoparticles, binary counterparts (CoS, NiS), and most highly active bifunctional catalysts described in the literature. The superior catalytic performance of NiCo 2 S 4 HSs is mainly ascribed to its unique hollow structure, which increases molecular diffusion and adsorption, as well as the synergistic effect of Ni and Co, which offers richer redox reaction sites. Importantly, this strategy may facilitate the design and preparation of excellent bifunctional nonprecious metal electrocatalysts in various domains.