FeNi (oxy)hydroxides embedded with high-valence Mo atoms: A efficient and robust water oxidation electrocatalyst.

The incorporation of high-valence transition metal atoms into FeNi (oxy)hydroxides may be a promising strategy to regulate the intrinsic electronic states, thereby reducing the thermodynamic barrier and accelerating oxygen evolution reaction (OER). Here, a high-valence Mo atoms doping route is proposed by an efficient self-reconstruction strategy to prepare MoFeNi (oxy)hydroxides for efficient alkaline OER. By using borides (MoNiB) as sacrificial template and Mo source, FeNi (oxy)hydroxides nanoflakes embedded with high-valence Mo atoms (MoFeNi) is successfully synthesized, which can modulate the electron coordination to improve the intrinsic catalytic activity. Remarkably, the obtained MoFeNi exhibits extremely low overpotential (η100 = 252 mV and η500 = 288 mV) and small Tafel slope (18.35 mV dec-1). The robust catalyst can run stably for hours at 500 mA cm-2. Characterization results and theoretical calculations confirmed that the addition of high-valence Mo effectively modulated the intrinsic electronic structure of metal sites and optimized the adsorption/desorption energy of the intermediates, accelerating OER reactions kinetics. By coupling MoFeNi anode with Pt/C cathode, anion exchange membrane (AEM) electrolyser can operate stably at 500 mA cm-2 with about less than 2.2 V. This research introduces a novel approach to develop ideal electrocatalysts through the incorporation of high-valence molybdenum species.

Motivating borate doped FeNi layered double hydroxides by molten salt method toward efficient oxygen evolution.

The incorporation of borate is a beneficial strategy to improve the catalytic activity of transition metal-based electrocatalyts for oxygen evolution reaction (OER). However, how to efficiently introduce borate has always been a challenge. Here, a facile and scalable molten salt method is developed to successfully dope borate into FeNi layered double hydroxides (FeBi@FeNi LDH) for efficient OER. The molten salt method can not only promote the formation of evenly dispersed nano-pompous FeBi precursor, thus providing the possibility to realize the direct doping of borate and the increase of mass, charge transfer and oxygen evolution active sites in FeNi LDH, but also promote the in-situ growth of FeBi@FeNi LDH on the conductive iron foam, improvingconductivity and stability of the material. The results indicate that the synthesized FeBi@FeNi LDH shows enhanced OER activity by delivering current densities of 10 and 100 mA cm-2 at low overpotentials of 246 and 295 mV and showing a small Tafel slope of 56.48 mV dec-1, benefiting from the optimization of geometric structure of active sites as well as the adjustment of electron density by borate doping especially in the case of molten salt. In addition, the sample can maintain durability at an industrial current density of 100 mA cm-1 for 90 h. This work provides a new way for the construction of efficient catalysts using boron doping assisted by molten salt.

Amorphous-crystalline cobalt phosphide hollow nanocubes induced by dual ligand environment for highly efficient hydrogen evolution.

CoP is one of the most promising catalysts for catalyzing hydrogen evolution reaction. The foremost issue is how to improve intrinsic activity by regulating electronic structure at the molecular level. Herein, utilizing selective combination of EDTA and Co2+, an amorphous-crystalline CoP with lower valence cobalt and hollow porous structure which induced by dual ligand environment is successfully synthesized via microwave heating and following phosphating process. Synthesize CoPBA from EDTA3+ and Co3+ in a ratio of 1:1 and followed by phosphating (ECP-1) exhibits excellent performance for HER in alkaline media, requiring 173 mV to achieve 10 mA cm-2. The enhanced catalytic activity may be ascribed to the amorphous-crystalline crystal structure with enlarged exposure of active sites and the hollow porous framework induced by EDTA, as well as the homogeneously distribution of (111) plane, on which the change of free energy on both Co bridge sites and P top sites is close to zero when adsorbing hydrogen. Besides, its great catalytic stability has been evaluated via 1000 cycles of CV measurement. The possible mechanism of valence state regulation of cobalt ions in CoP is discussed in detail. Furthermore, the optimal ratio of EDTA to Co2+ and different precursor states are explored reasonably.