Mottoh was released from the Academy at Arsenal in the summer of 2022 and was subsequently taken in on a two-year scholarship by the Academy at Portsmouth following a successful trial. He scored 15 goals in his first 18 appearances playing wing-back for the academy.[1] He made his senior debut as a second-year scholar on 8 August 2023, coming on as an 86th-minute substitute in a 3–1 win at Forest Green Rovers in the EFL Cup.[2] At the time the 16 year-old was the youngest second-year scholar in the country.[3] He earned his first start at Fratton Park on 23 August, in a 3–3 draw with Fulham U21 in the EFL Trophy.[4]