No abstract

Exploring sustainable and efficient electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is necessary for the development of fuel cells and metal-air batteries. Herein, we report a bimetal Fe/Mn-N-C material composed of spinel MnFeO/metallic Fe hybrid nanoparticles encapsulated in N-doped mesoporous hollow carbon nanospheres as an excellent bifunctional ORR/OER electrocatalyst in alkaline electrolyte. The Fe/Mn-N-C catalyst is synthesized via pyrolysis of bimetal ion-incorporated polydopamine nanospheres and shows impressive ORR electrocatalytic activity superior to Pt/C and good OER activity close to RuO catalyst in alkaline environment. When tested in Zn-air battery, the Fe/Mn-N-C catalyst demonstrates excellent ultimate performance including power density, durability, and cycling. This work reports the bimetal Fe/Mn-N-C as a highly efficient bifunctional electrocatalyst and may afford useful insights into the design of sustainable transition-metal-based high-performance electrocatalysts.

Active electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are decisive for achieving efficient energy conversion from electricity to hydrogen fuel through water electrolysis. In this study, tremella‐like Ru‐doped Co‐V layered double hydroxide nanosheets on Ni Foam (Ru‐CoV‐LDH@NF) was fabricated by a one‐pot solvothermal reaction. As‐prepared Ru‐CoV‐LDH@NF, with a nominal Ru loading of around 51.6 μg cm−2 exhibits excellent bifunctional catalytic activity towards HER and OER in alkaline media. To accomplish a current density of 10 mA cm−2, it demands 32 mV and 230 mV overpotentials for HER and OER, respectively. The alkali electrolyzer utilizing Ru‐CoV‐LDH/NF as bifunctional electrocatalyst affords 10 mA cm−2 electrolytic current density at an extremely low cell voltage of 1.50 V, showing excellent performance compared to a Pt/C−RuO2‐based electrolyzer and many other bifunctional electrocatalyst‐based ones. The incorporation of Ru changes the morphology of the resultant nanosheets to offer high electrochemical surface areas for electrocatalysis; at the same time, it significantly boosts the intrinsic HER/OER electrocatalytic activity. For HER, the energy barrier of the Volmer step is efficiently reduced upon Ru doping, whereas the Ru dopants optimize the absorption strength of *O intermediates to facilitate the OER process. This work offers a feasible means to optimize the Co‐based hydroxide materials for improved electrocatalysis in overall water splitting.

Transition metal phosphides (TMPs) demonstrate great potential for hydrogen evolution reaction (HER) electrocatalysis, but their activities need further improvement. Herein we report a novel Au incorporation strategy to boost the HER catalytic performance of CoP. As a proof of concept, heterostructured Au/CoP nanoparticles dispersed on nitrogen-doped carbon with unique porosity, denoted as Au/CoP@NC-3, are synthesized by thermal treatment of Au-nanoparticle-incorporated ZIF-67 precursor. It shows excellent HER activity as well as good durability in acidic and alkaline condition, respectively, greatly outperforming its Au-free analogue, namely, CoP@NC. In-depth analysis suggests that the improved HER activity of Au/CoP@NC-3 is attributed to the presence of Au nanoparticles which enlarge the electrochemical active surface areas and adjust the electronic structure of active CoP species to enhance the water adsorption and optimize H adsorption for the accelerated HER process.

It is desirable yet challenging to develop highly active and durable hydrogen evolution reaction (HER) electrocatalysts with Pt-comparable activity for future energy devices. In this work, we report Ru2P nanoparticle decorated P/N dual-doped carbon nanofibers on carbon cloth (Ru2P@PNC/CC-900) as a highly efficient and durable hierarchical HER electrocatalyst in both acidic and alkaline media. Electrochemical tests show that this Ru2P@PNC/CC-900 possesses Pt-comparable HER activity to support 10 mA cm–2 HER current density at low overpotential of 15 and 50 mV in acidic and alkaline condition, respectively. Density functional theory calculations reveal that coupling Ru2P nanoparticles with heteroatom-doped carbon fibers leads to enhanced intrinsic HER activity. The integrative hierarchical architecture further endows high surface areas with good mechanical robustness to support abundant catalytically active sites and possesses excellent electrical conductivity and efficient access for mass transportation to facilitate the HER process.