Reversing a Platinum Micromotor by Introducing Platinum Oxide

Abstract Understanding and controlling the swimming direction of a synthetic nano‐ and micromotor holds fundamental and applied significance. Here, we focus on platinum‐containing Janus colloids that catalytically decompose H 2 O 2 into O 2 , an archetypical model of chemical micromotor. We discover that platinum oxides (primarily PtO) are produced on Pt films sputter‐coated in O 2 plasma, and PtO reverses the motor possibly by self‐electrophoresis. Using this knowledge, micromotors moving in either direction were fabricated by intentionally introducing or removing PtO. These findings challenge the conventional wisdom that a Pt micromotor is powered by Pt alone, and open up new avenues for controlling the swimming directions of a micro‐ and nanomachine.