One-pot solvothermal synthesis of highly catalytic Janus transition metal phosphides (TMPs) for high performance OER

Green hydrogen is a highly efficient and affordable energy carrier for imminent energy supply. First time, this work demonstrates the crystalline TMPs synthesized by one-pot solvothermal method. M₁₂P₅ (M = Ni, Co, Ni-Co) nanoparticles deposited on conducting surface of nickel foam (M₁₂P₅@NF) serving as highly auspicious oxygen evolution reaction (OER) electrode. Our findings demonstrate that the M₁₂P₅@NF electrodes can be cast-off as capable Janus catalysts for OER. The onset potential for OER of Janus Co₁₂P₅ befalls at 1.29 V_RHE and possesses a current density of 10 mAcm⁻² just at overpotential of only 160 mV. Intriguingly, Co₁₂P₅ reveals the low Tafel slope value of 33 mVdec⁻¹. The onset potential for Ni₁₂P₅, (Ni-Co)₁₂P₅ electrodes are 1.30 and 1.46 V_RHE, decade current density obtained just at bias of 300 and 340 mV, respectively. These electrocatalysts unveil the worthy electro-active zone, as compared to that of other reported nickel and cobalt based materials. These electrocatalysts also sustain an amazing stability during long-term stability experiments. Ni, Co and (Ni-Co)-phosphides show high TOF value of 8.5, 11.37 and 5.1 s⁻¹ and mass activity of 119, 68 and 48 A g⁻¹ respectively at over potential of 350 mV which is an indicative of rapid electrochemical reaction and charge transfer kinetics of electrocatalyst. The catalytic enactment of Co₁₂P₅ is several folds superior than avant-garde catalysts (RuO₂ and IrO₂) under the similar set of conditions. The greater OER activity of M₁₂P₅ at such low overpotential is attributed to the mutual consequence of high electroactive sites at exterior of catalytic surface and auspicious interaction generated among intrinsically dynamic 3d-transition metal i.e. Ni, Co and phosphorous. TMPs are efficient and non-precious metal centered materials, which unwraps new prospects to exploit water electrolysis for green hydrogen fuel.