Rational design and fabrication of efficient catalysts for overall water splitting in an integrated electrolyzer are essential for energy storage and conversion. Herein, an ultra-small substitutional Zn-doped Ru/RuO2 heterostructure (5.6 nm) is synthesized through a facile pyrolyzing strategy as an efficient bi-functional electrocatalyst for water splitting in both acidic and alkaline media. Experiments demonstrate that introducing appropriate alien atoms into RuO2 with an amorphous state can effectively optimize the electron structure and expose abundant defects, and thus increasing the number of active sites and improving the intrinsic activity of RuO2 for the oxygen evolution reaction (OER). In addition, the high hydrogen adsorption capability of metallic Ru makes Ru-RuO2 heterointerface suitable for water splitting. Notably, the Ru/ZnRuO2 displays low overpotentials at 10 mA cm(-2) with only 184 mV for OER in 0.5 m H2SO4 and 35 mV for HER in 1.0 m KOH. Besides, the as-synthesized Ru/ZnRuO2 displays cell voltages of 1.540 and 1.567 V (at 10 mA cm(-2)) for water splitting with remarkable durability for more than 220 and 100 h, respectively, in acidic and alkaline media. This work provides a facile strategy for designing pH-universal electrocatalysts toward overall water splitting.

Surface reconstruction inevitably occurs during pre-catalysis for the oxygen evolution reaction (OER); however, obtaining OER electrocatalysts with high performance and stability remains a challenge. In this study, we have developed a bimetallic leaching-induced surface reconstruction strategy to fabricate efficient electrocatalysts for water oxidation. Microcolumn arrays consisting of α-CoMoO4, K2Co2(MoO4)3, Co3O4, and CoFe2O4 four-phase oxides were integrated as pre-catalyst by a hydrothermal, ion-exchange, and subsequent annealing process. In situ Raman spectroelectrochemical and ex situ X-ray diffraction (XRD) studies revealed that the rapid dissolution of the unstable component K2Co2(MoO4)3 triggered the adaptive leaching of Mo and K, which accelerated the transformation of the surface-enriched α-Co(OH)2 to the active phase of CoOOH at low voltage. Furthermore, the stable CoFe2O4 component couples the reconfigured new phase CoO with the amorphous layer CoOOH to form a compact hierarchical structure of CoFe2O4@CoO@CoOOH, which plays the role of a nanofence and effectively prevents the catalyst from over-reconstruction, thus achieving excellent catalytic stability. This work provides a novel idea for designing OER catalysts with excellent activity and stability at high current densities.

Nickel molybdate is a promising non-noble metal candidate for alkaline hydrogen evolution reaction (HER), but its insufficient activity due to its low conductivity and slow reaction kinetics hinders its application for large-scale commercial hydrogen production. Here, we report an efficient self-supporting electrocatalyst consisting of NiMoO4 nanorods modified by MoOy with abundant internal oxygen vacancies and epitaxially grown NiTex with high specific surface area for alkaline HER. Benefiting from the structural advantages of nanorods/nano-sheets integrated electrode, a larger specific surface area and abundant active centers can be provided for the HER. Such constructed NiTex/MoOy/NiMoO4 catalyst achieves a low overpotential of 59 mV to drive a current density of 10 mA cm-2 and a low Tafel slope of 32.8 mV dec- 1 in 1.0 M KOH solution with sustainable durability. Additionally, a two-electrode electrolytic cell system assembled with NiTex/MoOy/NiMoO4 and NiMoO4 employed as cathode and anode, respectively, extraordinary performance with a voltage of 1.49 V at a current density of 10 mA cm-2 was achieved in alkaline electrolyte. This work demonstrates a novel idea for metalloid Te-modified transition metal oxides, which is expected to expand the family of stable and efficient transition metal oxide (such as CoMoO4, Co3O4, NiCo2O4, etc.)-based catalysts for energy electrocatalysis.

Bifunctional oxygen electrocatalysts that hold outstanding activity and stability are highly crucial for the development of efficient rechargeable Zn-air batteries. Herein, cobalt-molybdenum-based bimetallic carbide and cobalt nanoparticles embedded N-doped carbon nanocages are synthesized via the pyrolysis of functionalized zeolitic imidazolate framework precursor originated from zeolitic imidazolate framework sequentially coated with polydopamine and phosphomolybdic acid. Furthermore, we revealed the composition-performance relationship based on the exploration of bifunctional performance on the pyrolysis products. More importantly, the synergy of multiple active sites with hollow structure gives the prepared catalyst a low overpotential (284 mV) for oxygen evolution reaction and high half-wave potential (0.865 V) for oxygen reduction reaction, besides an excellent bifunctional durability. Furthermore, the prepared catalyst as a cathode electrocatalyst grants the assembled rechargeable Zn-air batteries a high open-circuit voltage, power density, specific capacity, and remarkable charge-discharge cycle stability. This work provides a strategy for the integration and active-adjustment of bifunctional catalyst and its potential applications in water splitting and other catalytic reactions.

Efficacious regulation of the geometric and electronic structures of carbon nanomaterials via the introduction of defects and their synergy is essential to achieving good electrochemical performance. However, the guidelines for designing hybrid materials with advantageous structures and the fundamental understanding of their electrocatalytic mechanisms remain unclear. Herein, superfine Pt and PtCu nanoparticles supported by novel S,N-co-doped multi-walled CNT (MWCNTs) were prepared through the innovative pyrolysis of a poly(3,4-ethylenedioxythiophene)/polyaniline copolymer as a source of S and N. The uniform wrapping of the copolymer around the MWCNTs provides a high density of evenly distributed defects on the surface after the pyrolysis treatment, facilitating the uniform distribution of ultrafine Pt and PtCu nanoparticles. Remarkably, the Pt1Cu2/SN-MWCNTs show an obviously larger electroactive surface area and higher mass activity, stability, and CO poisoning resistance in methanol oxidation compared to Pt/SN-MWCNTs, Pt/S-MWCNTs, Pt/N-MWCNTs, and commercial Pt/C. Density functional theory studies confirm that the co-doping of S and N considerably deforms the CNTs and polarizes the adjacent C atoms. Consequently, both the adsorption of Pt1Cu2 onto the SN-MWCNTs and the subsequent adsorption of methanol are enhanced; in addition, the catalytic activity of Pt1Cu2/SN-MWCNTs for methanol oxidation is thermodynamically and kinetically more favorable than that of its CNT and N-CNT counterparts. This work provides a novel method to fabricate high-performance fuel cell electrocatalysts with highly dispersed and stable Pt-based nanoparticles on a carbon substrate.