Herein, a surfactant- and additive-free strategy is developed for morphology-controllable synthesis of cobalt pyrophosphate (CoPPi) nanostructures by tuning the concentration and ratio of the precursor solutions of Na P O and Co(CH COO) . A series of CoPPi nanostructures including nanowires, nanobelts, nanoleaves, and nanorhombuses are prepared and exhibit very promising electrocatalytic properties toward the oxygen evolution reaction (OER). Acting as both reactant and pseudo-surfactant, the existence of excess Na P O is essential to synthesize CoPPi nanostructures for unique morphologies. Among all CoPPi nanostructures, the CoPPi nanowires catalyst renders the best catalytic performance for OER in alkaline media, achieving a low Tafel slope of 54.1 mV dec , a small overpotential of 359 mV at 10 mA cm , and superior stability. The electrocatalytic activities of CoPPi nanowires outperform the most reported non-noble metal based catalysts, even better than the benchmark Ir/C (20%) catalyst. The reported synthesis of CoPPi gives guidance for morphology control of transition metal pyrophosphate based nanostructures for a high-performance inexpensive material to replace the noble metal-based OER catalysts.

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CoS, a low cost and efficient electrocatalyst for oxygen evolution reaction (OER), has attract great research interest but its electrosynthesis to delicately tune the nanostructures has not been carried out. Herein, for the first time by the use of potassium thiocyanate (KSCN) as sulfur source, CoS nanosheets are time‐controlled electrosynthesized and further evolved to a 3D flower‐like nanostructure, in which KSCN plays a critical role. With a deposition time of 1200s, the catalyst shows excellent catalytic activity toward OER, achieving a small Tafel slope of 55 mV dec−1 and only requires an overpotential of 310 mV to deliver a current density of 10 mA cm−2, better than the benchmark IrO2 and other electrodeposited cobalt sulfide catalysts. The enhancement mechanism is attributed to the unique nanostructure offering a large electroactive surface while allowing reactants accessing the reaction surface and the produced oxygen bubble escaping out for a fast electrode kinetics toward OER.