[3] With Marcus Britt he won the open men's national coxless pair title at the 2023 Australian Rowing Championships.

[5] He first made state selection for New South Wales in the 2013 youth eight contesting the Noel Wilkinson Trophy at the Interstate Regatta within the Australian Rowing Championships.

[7] In 2017, he was selected to stroke the New South Wales senior men's eight competing for the King's Cup at the Interstate Regatta.

[12] The following year at the 2016 World Rowing U23 Championships in Rotterdam he was seated in the Australian U23 eight which raced to a seventh place finish.

That crew placed third in their heat and then in the repechage they went out hard and alongside New Zealand they surprised the Lithuanian world champions knocking them out of the final.

In the final the Australian quad rowed through most of the field from the 1000m mark and finished in second place for a silver world championship medal.

[12] In 2019, he was selected with Caleb Antill, David Watts and Cameron Girdlestone to row Australia's quad scull for the 2019 international season.

Purnell was selected to join the former two-time world champions Jack Hargreaves, Alexander Hill and Spencer Turrin in that boat.

With Purnell steering straight and true from the bow seat the Australians kept their composure and held off the Romanians in a tight finish, taking the gold in an Olympic best time.

[12] In March 2022 Purnell, Hargreaves, Turrin and Jack O'Brien were selected as the men's four in the Australian team for the 2022 international season and the 2022 World Rowing Championships.