Nanoarchitectonics of binary transition metal phosphides embedded in carbon fibers as a bifunctional electrocatalysts for electrolytic water splitting

The path to the future of energy is shifting from fossil fuels to renewables. Hydrogen as the product of water electrolysis is a flexible and clean energy carrier, since it not only offers the prospect of large green electricity storage capacities for weeks or months but also a broad spectrum of other options for industry decarbonization. NiCoP bimetallic phosphide nanoparticles incorporated into the carbon fibres (CF) were evaluated in this work as the most active materials within the investigated trinity NiCoP CF, FeNiP CF and FeCoP CF. Electrospinning was implemented as low cost, large-scale and versatile production technology. NiCoP CF as breakthrough bifunctional catalyst was studied in 1 M KOH as well as 0.5 M H 2 SO 4 solutions simulating environments of alkaline and proton exchange membrane (PEM) electrolysis, respectively. High electrocatalytic activity was detected for material prepared in both environments, resulting in cell voltage at the current density of 10 mA/cm -2 as low as 1.71 V and 1.51 V in KOH and H 2 SO 4 solution, respectively. Corresponding overvoltage has reached 257 mV for HER and 300 mV for OER, whereby the respective Tafel slopes acquire the values of 38.6 mV/dec for HER and 81 mV/dec for OER, respectively. An excellent stability in acidic environment was proven indicating high material potential for a practical utilization of these materials in water electrolysis energy conversion processes. • Preparation of NiCoP, FeNiP, FeCoP nanoparticles encapsulated in carbon fibers. • Needle-less electrospinning technology was used. • NiCoP carbon fibers exhibit superior HER catalytic performance in 1.0 M KOH. • NiCoP carbon fibers exhibit bifunctional catalytic performance in 0.5 M H 2 SO 4 .