Filed Pursuant to Rule 424(b)(3)
Registration No. 333-258340
PROSPECTUS SUPPLEMENT NO. 6
(to prospectus dated
August 10, 2021)
Up to 19,300,751 Shares of Class A Common Stock Issuable Upon the Exercise of Warrants
Up to 77,272,414 Shares of Class A Common Stock
Up to 8,014,500 Warrants to Purchase Class A Common Stock
This prospectus supplement is being filed to update and supplement the information contained in the prospectus dated August 10, 2021 (as
supplemented or amended from time to time, the “Prospectus”), with the information contained in our Current Report on Form 8-K, filed with the Securities and Exchange Commission (“SEC”) on
January 12, 2022 (the “Current Report”), other than information included in Item 2.02 and Exhibit 99.1, which was furnished and not filed with the SEC. Accordingly, we have attached the Current Report to this prospectus supplement.
The Prospectus and this prospectus supplement relate to the issuance by us of up to an aggregate of 19,300,751 shares of Class A
Common Stock, par value $0.0001 per share (“Class A Common Stock”), which consists of (i) up to 8,014,500 shares of Class A Common Stock that are issuable upon the exercise of 8,014,500 warrants (the “private
placement warrants”) issued in a private placement in connection with the initial public offering of Decarbonization Plus Acquisition Corporation (“DCRB”) and upon the conversion of a working capital loan by the Sponsor (as defined in
the Prospectus) to DCRB and (ii) up to 11,286,251 shares of Class A Common Stock that are issuable upon the exercise of 11,286,251 warrants originally issued in DCRB’s initial public offering. The Prospectus and this prospectus
supplement also relate to the offer and sale from time to time by the selling securityholders named in the Prospectus, or their permitted transferees, of (i) up to 77,272,414 shares of Class A Common Stock (including up to 5,293,958 shares
of Class A Common Stock issuable upon the satisfaction of certain triggering events (as described in the Prospectus) and up to 326,048 shares of Class A Common Stock that may be issued upon exercise of the Ardour Warrants (as defined in
the Prospectus)) and (ii) up to 8,014,500 private placement warrants.
This prospectus supplement updates and supplements the
information in the Prospectus and is not complete without, and may not be delivered or utilized except in combination with, the Prospectus, including any amendments or supplements thereto. This prospectus supplement should be read in conjunction
with the Prospectus and if there is any inconsistency between the information in the Prospectus and this prospectus supplement, you should rely on the information in this prospectus supplement.
Our Class A Common Stock and warrants are traded on the Nasdaq Global Select Market under the symbols “HYZN” and
“HYZNW,” respectively. On January 11, 2022 the closing price of our Class A Common Stock was $6.81 and the closing price for our public warrants was $1.77.
Investing in our securities involves risks that are described in the “Risk Factors” section beginning on page 7 of the
Prospectus.
Neither the SEC nor any state securities commission has approved or disapproved of the securities to be issued under
the Prospectus or determined if the Prospectus or this prospectus supplement is truthful or complete. Any representation to the contrary is a criminal offense.
The date of this prospectus supplement is January 12, 2022.