Scalable Synthesis of Pt Nanoflowers on Solution‐Processed MoS2 Thin Film for Efficient Hydrogen Evolution Reaction

Nanostructuring of Pt nanocatalysts increases the surface‐to‐volume ratio, thus enabling efficient usage of Pt for hydrogen evolution reaction (HER). Direct electrochemical reduction of Pt on the electrode can produce nanostructured Pt catalysts, which has been time‐consuming for the conventional colloidal synthesis. However, carbon‐based growth templates commonly used to create Pt nanoparticles offer limited control over morphologies and HER performance. Herein, a facile electrochemical synthesis of Pt nanoflowers (NFs) with well‐defined petals is presented. Semiconducting MoS2 nanosheets are solution processed into a film on a carbon paper (CP) to synthesize Pt NFs upon reduction of Pt precursor. The Pt NFs show higher HER activities than spherical or spiky Pt nanoparticles because of their larger active surface area and enable faster release of hydrogen bubbles during HER. By generating sulfur vacancies and MoOx on the MoS2 template using a reactive ion etching, the areal density and spatial uniformity of Pt NFs can be greatly enhanced and a mass activity can be achieved more than 10 times as high as that of the conventional Pt/C electrode. Multiple electrodes with nearly similar electrochemical properties can be repeatedly produced by using a single precursor solution, which highlights the cost‐efficiency and scalability of our synthesis strategy.